WO2015120264A1

WO2015120264A1 - Process for the preparation of a c5-enriched juice stream

Info

Publication number: WO2015120264A1
Application number: PCT/US2015/014808
Authority: WO
Inventors: Zachary LOSORDO; Justin Van Rooyen; Kevin Wenger; Lee Lynd; John Mcbride
Original assignee: Enchi Corporation
Priority date: 2014-02-07
Filing date: 2015-02-06
Publication date: 2015-08-13
Also published as: EP3137508A1; EP3137508A4

Abstract

The present disclosure provides a process for preparing a juice stream comprising sucrose and hemicellulose (C5) sugars, wherein the juice stream, after typical workup, is suitable for cofermentation to produce ethanol.

Description

PROCESS FOR THE PREPARATION OF A C5-ENRICHED JUICE STREAM

BACKGROUND OF THE INVENTION

[0001] Sugar (sucrose) and ethanol production from sugarcane are often conjoined processes, with some sugar production facilities either directly or indirectly further processing some or all of their sucrose for ethanol production. Such conjoined production is observed largely in Brazil, where ethanol demand is high. The demand for ethanol is driven in large measure by the use of ethanol in place of, or in combination with, refined hydrocarbon fuels.

[0002] When sucrose is extracted from sugarcane (for fermentation or otherwise), the process results in waste, as the sugarcane itself is a fibrous stalk that typically contains less than about 20% soluble sugars, and typically about 15% soluble sugar. The wet, fibrous material remaining after sugar is extracted from the stalk can be dried to appropriate levels (typically around 50%> by weight) and used as fuel to generate energy to support cane processing. Alternatively, remaining material can be used in paper production, serving as a source of pulp.

[0003] Although the present sugarcane processing techniques are capable of producing commercial quantities of sugar for consumption and ethanol production, the demand for ethanol continues to grow commensurate with consumers preference for greener fuels and government mandated ethanol blends. Despite the increased demand for ethanol, the sugar content in sugarcane has remained relatively constant. As a result, ethanol producers seeking to increase ethanol production must buy additional sugarcane, expand production facilities, or both. As more ethanol producers seek additional sugarcane to produce additional ethanol, the aggregate cost of sugarcane increases, ultimately driving the price of sugar and ethanol up.

[0004] In order to offset the cost increases in raw materials associated with increased demand, it would be desirable to have a process capable of extracting additional materials suitable for fermentation to ethanol from the sugarcane already available. The present disclosure provides such a process. BRIEF SUMMARY OF THE INVENTION

[0005] The present disclosure provides a procedure that allows bagasse and/or cane trash to be "pretreated" and subsequently extracted to provide hemicellulose sugars and sucrose for further processing into ethanol. The disclosed process reduces the capital and operating costs of ethanol production through high levels of integration with pre-existing sugarcane processing equipment. Further, although the process provides increased ethanol production, the process has minimal impact on downstream energy extractable from bagasse waste, e.g. through burning.

[0006] More specifically, the process disclosed herein comprises treating bagasse, cane trash, or a combination thereof in a pretreatment reactor to hydrolyze hemicellulose already present in the cane trash and/or bagasse. This pretreatment process generates a C5-enriched material that comprises hemicellulose sugars, such as xylose and arabinose, as well as some C6 sugars present in lower amounts, such as glucose, mannose, and galactose. The C5-enriched material can further include lignin and degradation products such as acetic acid, furfural, and hydroxymethylfurfural ("HMF").

[0007] The C5-enriched material is then subjected to an extractive process, such as milling or a diffuser, where sucrose not previously extracted from the C5-enriched materials and the hemicellulose sugars resulting from the pretreatment process are co- extracted. This extraction process results in a C5 -enriched juice stream comprising hemicellulose sugars and sucrose which can then be processed into ethanol using preexisting equipment/processes and one or more yeast strains capable of expressing enzymes suitable for fermenting both sucrose and hemicellulose sugars into ethanol. Exemplary yeast strains are, for example, disclosed in US 2013/0323822 and PCT/US2013/000090, the entireties of which are incorporated herein by reference.

[0008] In certain embodiments, the present disclosure provides a process for preparing a

C5 -enriched juice stream, the process comprising: pretreating bagasse, cane trash, or a combination thereof to produce a C5-enriched material; and extracting the C5-enriched material to produce a C5 -enriched juice stream.

[0009] In certain embodiments, the pretreating comprises treating the bagasse with steam for about 5 to about 15 minutes at a temperature of from about 150 °C to about 200 °C.

[0010] In certain embodiments, the extracting comprises milling the C5 -enriched materials or passing the C5 -enriched materials into a diffuser. [0011] In some embodiments, the milling comprises subjecting the C5 -enriched material to at least one milling stage and washing the C5 -enriched material subjected to milling with imbibition water to produce the C5 -enriched juice stream.

[0012] In some embodiments, the at least one milling stage comprises two, three, four, five, or six milling stages.

[0013] In certain embodiments, the at least one milling stage comprises four milling stages and the C5-enriched materials are subjected to countercurrent washing.

[0014] In some embodiments, the extracting comprises passing the C5-enriched material into a diffuser.

[0015] In some embodiments, the C5-enriched juice stream comprises sucrose and hemicellulose sugars.

[0016] In some embodiments, the C5 -enriched juice stream comprises from about 1% to about 50% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

[0017] In some embodiments, the C5-enriched juice stream comprises from about 3% to about 33% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

[0018] In still other embodiments, the C5-enriched juice stream comprises from about 1% to about 5% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

[0019] In another embodiments, the process described herein further comprises subjecting the C5 -enriched juice stream or a stream derived from the C5 -enriched juice stream to cofermentation.

[0020] In another embodiments, the present disclosure provides a process for preparing a

C5 -enriched juice stream, the process comprising: feeding sugarcane to a first milling stage to produce a primary juice stream and bagasse; pretreating the bagasse produced by the first milling stage to produce a C5-enriched material; and extracting the C5-enriched material to produce a C5 -enriched juice stream.

[0021] In some embodiments, extracting the C5 -enriched material to produce a C5- enriched juice stream comprises feeding the C5-enriched material to a diffuser. [0022] In other embodiments, extracting the C5-enriched material to produce a C5- enriched juice stream comprises subjecting the C5 -enriched material to at least one, at least two, at least three, at least four, at least five, or at least six additional milling stages.

[0023] In some embodiments, the process further comprises combining the C5-enriched juice stream with the primary juice stream.

[0024] In certain embodiments, the C5 -enriched juice stream and the primary juice stream are not combined.

[0025] The present disclosure further provides a process for preparing a C5 -enriched juice stream comprising: feeding sugarcane to a first milling stage to produce a primary juice stream and bagasse; feeding the bagasse to at least a second milling stage to produce a secondary juice stream and extracted bagasse; pretreating the extracted bagasse to produce a C5-enriched material; and extracting the C5-enriched material to produce a C5- enriched juice stream.

[0026] In some embodiments, the process further comprises combining the secondary juice stream and the C5 -enriched juice stream to produce a combined juice stream.

[0027] In some embodiments, the process further comprises processing the combined juice stream to produce a juice stream suitable for cofermentation.

[0028] In certain embodiments, feeding the bagasse to at least a second milling stage to produce a secondary juice stream and extracted bagasse comprises feeding the bagasse to at least one, at least two, at least three, at least four, or at least five milling stages.

[0029] In some embodiments, the process described herein further comprises cofermenting the combined juice stream.

[0030] In some embodiments, the cofermenting comprises contacting the combined juice stream with a microorganism capable of fermenting xylose and sucrose.

[0031] In certain embodiments, the microorganism is M3799 or M5401.

[0032] In certain embodiments, the contacting is at a temperature of about 35 °C.

[0033] In still another embodiments, the present disclosure provides a C5-enriched juice stream prepared by the process of: pretreating bagasse, cane trash, or a combination thereof to produce a C5-enriched material; and extracting the C5-enriched material to produce a C5 -enriched juice stream. [0034] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the pretreating comprises treating the bagasse with steam for about 5 to about 15 minutes at a temperature of from about 150 °C to about 200 °C.

[0035] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the extracting comprises milling the C5 -enriched materials or passing the C5 -enriched materials into a diffuser.

[0036] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the milling comprises miling the C5 -enriched material in at least one milling stage and washing the C5 -enriched material subjected to milling with imbibition water to produce the C5-enriched juice stream.

[0037] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the at least one milling stage comprises two, three, four, five, or six milling stages.

[0038] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the at least one milling stage comprises 4 milling stages and wherein the C5-enriched materials are subjected to countercurrent washing.

[0039] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the extracting comprises passing the C5 -enriched material into a diffuser.

[0040] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the C5 -enriched juice stream comprises sucrose and hemicellulose sugars.

[0041] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the C5 -enriched juice stream comprises from about 1% to about 50% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

[0042] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the C5 -enriched juice stream comprises from about 3% to about 33% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

[0043] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the C5 -enriched juice stream comprises from about 1% to about 5% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

[0044] In certain embodiments, when the C5 -enriched juice stream is prepared according to the process described herein, the process further comprises subjecting the C5 -enriched juice stream or a stream derived from the C5 -enriched juice stream to co fermentation.

[0045] The present disclosure still further provides a sugar/ethanol production plant comprising: at least a first extractive stage for generating bagasse; a pretreatment reactor for generating a C5 -enriched material, wherein the pretreatment reactor is adapted to receive the bagasse from the at least a first extractive stage and, optionally, cane trash; at least a second extractive stage for generating a C5 -enriched juice stream, wherein the at least a second extractive stage is adapted to receive the C5 -enriched material; and a cofermentation reactor for fermenting the C5 -enriched juice stream.

[0046] In some embodiments, the at least a first extractive stage is at least a first milling stage.

[0047] In still other embodiments, the at least a second extractive stage is at least a second milling stage.

[0048] In a further embodiment, the at least a second extractive stage is a diffuser.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0049] The foregoing summary, as well as the following detailed description of the embodiments, will be better understood when read in conjunction with the appended drawings. For the purpose of illustration, the drawings may describe the use of specific embodiments. It should be understood, however, that the formulation is not limited to the precise embodiments discussed or described in the figures.

[0050] Figure 1 is a diagram of a standard sugarcane milling operation including five milling stages.

[0051] Figure 2 is a diagram showing a sucrose/ethanol production process using a diffuser modified to accommodate the process disclosed herein.

[0052] Figure 3 shows a block diagram of a C5 production and processing plant minimally integrated with a sugarcane ethanol plant, sharing only the biomass powerplant

[0053] Figure 4 shows a block diagram of a moderately integrated sugar/ethanol production process employing the process disclosed herein. [0054] Figure 5 shows a block diagram for a highly integrated ethanol production process employing the process disclosed herein.

[0055] Figure 6 is a diagram of a standard sugarcane milling operation including five milling stages, wherein the process described herein has been integrated into the process.

[0056] Figure 7 is a block diagram of sugarcane processing procedure wherein bagasse and/or cane trash is subject to pretreatment resulting in C5-enriched materials which can then be fed to an extractive process and extracted simultaneously with new sugarcane.

This process provides a combined juice stream comprising hemicellulose sugars and sucrose.

[0057] Figure 8 is a graph showing the efficacy of cofermentation of a combined juice stream.

[0058] Figure 9 is a graph showing the efficacy of cofermentation of molasses and xylose.

DETAILED DESCRIPTION OF THE INVENTION

[0059] The articles "a," "an," and "the" are used herein to refer to one or to more than one

(i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

[0060] As used herein, the term "bagasse" refers to completely or partially extracted sugarcane fiber.

[0061] As used herein, the term "cane trash" refers to materials remaining after harvesting sugarcane, including cane tops and leaves.

[0062] As used herein the term "feed supply" refers to bagasse, cane trash, or a combination thereof. The bagasse and/or cane trash can be shredded, crushed, or otherwise treated to make sucrose or hemicellulose sugars more susceptible to extraction.

[0063] The phrase "C5-enriched" means hemicellulose sugar enriched, particularly xylose and arabinose enriched. When the phrase C5-enriched is used to modify another term, e.g. "C5-enriched material," C5-enriched juice," etc, it is to be understood that object described as C5-enriched can further include other components, such as, but not limited to, lignin and degradation products, such as acetic acid, furfural, and hydroxymethylfurfural ("HMF"). An object described as C5-enriched can further include sucrose or sucrose derivatives, such as glucose and fructose. [0064] The term "sugar" means sucrose.

[0065] The phrase "hemicellulose sugar" means C5 sugars such as xylose and arabinose, and C6 sugars such as glucose, mannose, and galactose. In particular embodiments described herein, hemicellulose sugar can comprise at least about 70%, at least about 80%, at least about 90%>, at least about 93%, at least about 95%, or at least about 97% xylose and arabinose, by weight, of the total sugar concentration, while the remaining sugars can be, for example, a combination of C6 sugars also generated by pretreatment of the feed supply such as glucose, mannose, and/or galactose.

[0066] The present disclosure provides a process comprising treating a feed supply containing insoluble hemicellulose, cellulose, and lignin, as well as soluble sucrose at whatever level may be beneficial, in a pretreatment reactor to solubilize and hydrolyze the hemicellulose to oligomeric and monomeric hemicellulose sugars. This process results in a C5-enriched feed supply, which is then subjected to an aqueous extractive process, such as milling or a diffuser, wherein hemicellulose sugars and any sucrose in the C5-enriched feed supply are co-extracted into water. This extraction process results in a C5 -enriched juice stream comprising hemicellulose sugars and sucrose, which can then be processed into ethanol using, for example, one or more yeast strains capable of expressing enzymes suitable for fermenting both sucrose and hemicellulose sugars into ethanol.

[0067] In certain embodiments, the C5-enriched juice stream can comprise from about

1%) to about 50%) by weight hemicellulose sugars based on the total weight of sugars (hemicellulose sugars + other sugars) present in the stream. In other embodiments, the C5 -enriched juice stream can comprise from about 1% to about 45% by weight hemicellulose sugars based on the total weight of sugars present in the stream; from about 1%) to about 40%) by weight hemicellulose sugars based on the total weight of sugars present in the stream; from about 1% to about 35% by weight hemicellulose sugars based on the total weight of sugars present in the stream; or from about 1% to about 30% by weight hemicellulose sugars based on the total weight of sugars present in the stream. In a particular embodiment, the C5 -enriched juice stream can comprise from about 3% to about 33%) by weight hemicellulose sugars based on the total weight of sugars present in the stream. In a particular embodiment, the C5 -enriched juice stream can comprise from about 1%) to about 5% by weight hemicellulose sugars based on the total weight of sugars present in the stream. In a particular embodiment, the C5 -enriched juice stream can comprise from about 5% to about 50% by weight hemicellulose sugars based on the total weight of sugars present in the stream. In certain embodiments, the sugar comprising the non-hemicellulose sugar portion of the C5-enriched juice stream can be sucrose.

[0068] Although the process described herein can be employed separate and apart from a traditional sugar/ethanol manufacturing process, see, for example, Figure 3, in more typical embodiments, the process described herein will be integrated into an existing sugarcane processing setup as shown, for example, in Figures 4, 5, 6, and 7.

Mill Integration

[0069] In certain embodiments, the process of the present invention can be integrated into a sugarcane milling process. Sugarcane mills dominate the sugarcane ethanol industry in countries such as Brazil. Mills can comprise of a set of milling stages arranged in a series. The milling stages can comprise 3 roll mills, though other configurations are known in the art. A given process can include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or more milling stages, each including an appropriate number of roll mills or other milling implements. Figure 1, for example, describes a standard sugarcane milling process comprising 5 milling stages with each milling stage comprising 3 roll mills.

[0070] As shown in Figure 1 , the unprocessed sugarcane is fed into a shredder. From the shredder, the semi-processed sugarcane is fed to a first milling stage, which applies pressure to the cane to remove sucrose and water to give an aqueous primary juice stream that can contain from about 100 g/L to about 225 g/L sucrose. In some embodiments, the primary juice stream can comprise at least about 100 g/L, at least about 125 g/L, at least about 150 g/L, at least about 175 g/L, at least about 200 g/L, or at least about 225 g/L sucrose representing from at least about 35% to at least about 70%> of the total sucrose present in the cane stalks. In particular embodiments, the primary juice stream can comprise about 100 g/L, about 125 g/L, about 150 g/L, about 175 g/L, about 200 g/L, or about 225 g/L sucrose. Cane processed through this first milling stage results in bagasse.

[0071] The bagasse can then be passed through at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, or at least 12 additional milling stages, depending upon the configuration in a given plant. Between milling stages, the bagasse is washed with counter-current imbibition water to collect additional sucrose released from the bagasse as a result of the milling processes. This repeated processing results in a secondary juice stream that contains at least about 60 g/L, at least about 80 g/L, at least about 100 g/L, or at least about 120 g/L sucrose, representing from at least about 30% to at least about 65% of the total sucrose present in the cane stalks.

[0072] While the concentrations of the primary juice stream and secondary juice stream can vary, it is understood in the art, and within the skill of the ordinarily skilled artisan, to recover at least 90%>, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% of the sucrose present sugar cane using known techniques.

[0073] In certain plant configurations, sometimes referred to as "coproduct flexible plants," the primary juice stream is reserved for producing sugar for consumption, while the secondary juice or a combination of secondary juice and primary juice is used for ethanol production. In other embodiments, the primary and secondary juice streams can be fully or partially mixed, which is typical in ethanol only production facilities. Mixed juice streams are typically not used to produce sugar for consumption in view of the presence of certain impurities that can be difficult to remove during the processing of food grade sucrose.

[0074] The pretreatment process disclosed herein can be integrated into a multi-stage milling process of the type disclosed above in numerous ways. For example, in certain embodiments, the bagasse that would normally pass from the first milling stage to the second milling stage can be diverted to a pretreatement reactor before being directed to the second milling stage. See, for example, Figure 6. Alternatively, diversion of the bagasse to the pretreatment reactor can be carried out between milling stages 2 and 3, milling stages 3 and 4, milling stages 4 and 5, milling stages 5 and 6, milling stages 6 and 7, milling stages 7 and 8, milling stages 8 and 9, milling stages 9 and 10, milling stages 10 and 11, and so on - depending on the number of milling stages in a given setup and the efficiency of the mills. In particular, embodiments, the bagasse can be shifted to the pretreatment reactor when about 50%, about 55%, about 60%, about 65%, about 70%, about 80%, about 85%, about 90%, about 95%, about 96%, about 97%, or 98% or about 99% of the total sucrose originally present in the cane has been extracted from the cane and bagasse.

[0075] Determining when to shift bagasse to the pretreatment reactor depends on the stability of sucrose during the pretreatment process, and the efficiency of extraction achieved at each step in the starting process. For example, if the pretreatment process results in significant sucrose degradation, as much sucrose as possible should be extracted from the bagasse before passing it to the pretreatment reactor. Conversely, if pretreatment does not result in significant sucrose degradation, then the bagasse can be passed to the pretreatment reactor sooner.

[0076] For example, in some embodiments, where pretreatment results in less than about

8% sucrose degradation during the pretreatment process, the bagasse can be directed to the pretreatment reactor between milling stages 1 and 2 or milling stages 2 and 3. In some embodiments where pretreatment results in from about 8% sucrose degradation to about 10% sucrose degradation, the bagasse can be directed to the pretreatment reactor between milling stages 2 and 3 or milling stages 3 and 4. In some embodiments where pretreatment results in from about 10%> sucrose degradation to about 17% sucrose degradation, the bagasse can be directed to the pretreatment reactor between milling stages 3 and 4 or milling stages 4 and 5. In some embodiments where pretreatment results in from about 17% sucrose degradation to about 25% sucrose degradation, the bagasse can be directed to the pretreatment reactor between milling stages 4 and 5 or 5 and 6. In some embodiments where pretreatment results in greater than about 25% sucrose degradation, the bagasse can be directed to the pretreatment reactor between milling stages 5 and 6 or 6 and 7. In particular embodiments, the bagasse can be directed to the pretreatment reactor between milling stages 1 and 2.

[0077] Pretreatment provides C5 -enriched materials which can be fed back into the milling process at any appropriate stage, e.g. at the 2^nd, 3^rd, 4^th, 5^th, 6^th, or 7^th milling stages. In certain embodiments, the C5-enriched materials are returned to the milling process at the point just after the stage from which it was originally removed. This is exemplified, for example, in Figure 6, which shows C5 -enriched materials - resulting from pretreatment of bagasse fed to the pretreatment reactor after being processed through the first milling stage - being fed into the second milling stage.

[0078] When the C5 -enriched materials are returned later in the extractive pathway, additional extractive processes, such as additional mills, may be required to extract the desired quantity of hemicellulose sugars and sucrose in the C5 -enriched materials. Regardless of where the C5-enriched materials reenter the milling process, the C5- enriched materials can be subject to sufficient extractive processes to extract at least about 50%), at least about 55%, at least about 60%, at least about 65%, at least about 69%, at least about 74%, at least about 76%, at least about 78%, at least about 80%, at least about 85%), at least about 87%, at least about 90%, at least about 91%>, at least about 93%>, at least about 95%, or at least about 97% of the hemicellulose sugars solubilized during pretreatment.

[0079] The additional milling and extraction of the C5-enriched materials results in a C5- enriched secondary juice stream. This C5 -enriched secondary juice stream, which can also contain significant quantities of sucrose, can then, in certain embodiments, be combined with the primary juice stream for processing and treatment prior to cofermentation. As discussed elsewhere herein, combination of the primary juice stream and the C5 -enriched secondary juice stream provides additional efficiencies for cofermentation as compared to cofermentation of the C5 -enriched secondary juice stream by itself.

[0080] Although less energy efficient than the fully integrated embodiments disclosed above, in an alternative process, the materials subject to pretreatment can undergo extraction and dewatering separately from the primary and/or secondary juice streams. In this process, the C5-enriched materials resulting from pretreatment are subject to an extractive process separate and apart from the extractive processes shown, for example, in Figure 1, resulting in a C5 -enriched secondary juice stream that is not mixed with the primary and/or secondary juice streams from the traditional milling process. The C5- enriched secondary juice stream resulting from the separate extractive processes can then be fermented into ethanol separately from the primary and/or secondary juice streams resulting from the traditional milling processes. The resulting ethanolic mixture can then be recombined with sucrose-derived "wine" from primary and/or secondary juice streams from the traditional process for subsequent distillation and dehydration. See, for example, Figure 4. In a further alternative, the ethanol derived from the separate C5 -enriched juice stream can be dehydrated and distilled separately.

Diffuser Integration

[0081] The process described herein can also be integrated into sugarcane processing plants using diffuser technology. Although less prevalent in commercial settings, diffusers can be highly efficient in removing sucrose from sugarcane and typically employ anywhere from 6 to 15, though typically 12, extraction stages comprising a cross flow wash with extraction water. See, generally, Rein, Peter. Cane Sugar Engineering. Bartens, 2007. (ISBN-13 : 978-3870401108), the entirety of which is incorporated herein by reference. Unlike a milling process, however, diffusers operate continuously and do not permit removal of cane trash or bagasse from the diffuser mid-process. Thus, in order to integrate the process described herein into a sugarcane process employing a diffuser, bagasse and/or cane trash must be subject to pretreatment prior to entering the diffuser.

[0082] In other embodiments, mechanically treated sugarcane can be processed through one or more milling stages before being subject to pretreatment. In these embodiments, bagasse resulting from the milling process is subject to pretreatment (along with any optionally included cane trash) with the resulting C5-enriched materials fed into a diffuser.

[0083] Milling processes employed prior to pretreatment can be similar to the milling processes described elsewhere herein. Milling results in a primary juice stream, which can be processed into consumer grade sugar or ethanol, and bagasse. And if a second or subsequent milling stage is employed, a secondary juice stream can also be generated. As with milling processes discussed elsewhere herein, the number of milling stages can be adjusted, depending upon how sucrose present in the bagasse tolerates the pretreatment process. When low degradation is observed, i.e. less than about 10%, less than about 8%, or less than about 5% degradation, one or two milling stage can be employed, for example. In embodiments where sucrose degradation during pretreatment is greater than about 10%, at least 2, at least 3, at least 4, at least 5, at least 6, or at least 7 milling stages can be employed, for example. In certain embodiments, 1 milling stage is employed. In other embodiments, two milling stages are employed. As discussed elsewhere herein, the number of milling stages can be determined by how much sucrose needs to be extracted prior to pretreatment.

[0084] After undergoing the milling process described above, the resulting bagasse can be passed to the pretreatment reactor, along with any desired cane trash. After pretreatment, the resulting C5 -enriched materials can be loaded into a diffuser wherein a C5 -enriched secondary juice stream can be obtained. As noted previously, the extraction can provide at least about 50%>, at least about 55%, at least about 60%, at least about 65%), at least about 69%>, at least about 74%, at least about 76%, at least about 78%, at least about 80%, at least about 85%, at least about 87%, at least about 90%, at least about 91%, at least about 93%, at least about 95%, or at least about 97% of the hemicellulose sugars solubilized during pretreatment.

[0085] An example of the present process integrated with a diffuser, shown with both one and two milling stages, is exemplified in Figure 2. The lightning bolt in the figure identifies the bagasse take-off point for pretreatment. The C5-enriched secondary juice stream can then be recombined with the primary and/or secondary juice streams for further processing into ethanol.

[0086] In a further alternative, bagasse collected from the end of a diffuser run (or otherwise) and/or cane trash can be subject to pretreatment and the resulting C5-enriched materials can be fed directly to a diffuser where it can be processed by itself or mixed with fresh sugarcane. See, for example, Figure 7.

Pretreatment Conditions

[0087] Exemplary pretreatment conditions include any water-based processes with conditions that breaks down hemicellulose, but preserves hemicellulose sugars and permits high recoveries of the same. Suitable examples of pretreatment conditions and reactors are disclosed in, for example, Kaar, et al, Steam Explosion Of Sugarcane Bagasse As A Pretreatment For Conversion To Ethanol, Biomass and Bioenergy Vol. 14, No. 3, pp. 277-287, 1998; Hongdan, Z., et al, Enhancement Of Enzymatic Saccharification Of Sugarcane Bagasse By Liquid Hot Water Pretreatment, Bioresource Technology 143 (2013) 391-396; and Amores, I., et al, Ethanol Production from Sugarcane Bagasse Pretreated by Steam Explosion, Electronic Journal of Energy and Environment, Vol. 1 , No. 1, pp. 25-36, April, 2013, each of which is incorporated herein by reference in its entirety.

[0088] Conditions suitable for breaking down hemicellulose tend to be lower severity than conditions required to achieve, for example, reactive solids. In particular embodiments, the pretreatment severity can range from about 2.5 to about 4.5. In some embodiments, the pretreatment severity can range from about 3 to about 4.25. In still further embodiments, the pretreatment severity can range from about 3 to about 3.9. Within the noted severity range, treatment times and temperatures can range from about 5 to about 15 minutes at temperatures from about 150 °C to about 200 °C. In certain embodiments, the pretreatment severity is about 3.5. Many reactors are suitable for performing the pretreatment of the type required. Suitable examples include, but are not limited to, horizontal screw fed reactors and horizontal pandia-type reactors both with and without steam explosion.

[0089] In some embodiments, the quantity of hemicellulose sugar that can be solubilized during pretreatment is about 50%, about 60%, about 70%>, or about 80%> of the total hemicellulose sugar present in original feed material. In particular embodiments, about 5%>, about 10%), about 15%, or about 20%> of the hemicellulose sugar present in the feed material can be degraded during pretreatment.

Further Processing of the C5 -enriched Juice Stream

[0090] Once recovered, the C5 -enriched juice can be combined with other juice streams

(such as the primary juice stream and/or the secondary juice streams) or it can be treated separately. In any event, the C5-enriched juice stream can be treated to remove impurities and solids that are known to impact fermentation performance. Exemplary processes known to those of ordinary skill in the art include, but are not limited to, liming, heating, clarifying, filtering, and concentrating (using processes such evaporation and/or reverse osmosis).

Benefits of a Highly Integrated Process Including Cofermentation

[0091] As is appreciated in the art, sugar and ethanol production are energy intensive processes. And any proposed changes, particularly those that add steps and/or require additional energy input, must be analyzed in the context of the benefit of the increase processing efficiency versus the cost of the energy required to obtain process efficiency. It has now been found that the process disclosed herein only reduces waste bagasse's heating value by 20% and requires minimal thermal and electrical inputs to catalyze the ethanol reaction, meaning that the highly integrated process described herein can be employed without the need to resort to additional energy sources to drive certain reaction processes. Stated somewhat differently, the process described herein can, for example, produce ethanol at an energy cost of about 31 MJ/Gal whereas the standard procedure for preparing ethanol can do so at an energy cost of about 37 MJ/Gal. Thus, the integration of the present process can provide significant energy savings over prior processes.

[0092] In addition to providing energy benefits, and as noted previously, integrating the process described herein into a conventional ethanol production facility provides further benefits such as allowing an ethanol manufacturer to control the concentration of inhibitors in the C5-enriched juice stream that will be subjected to fermentation. For example, C5 enriched juice streams prepared from pretreated bagasse, in addition to containing fermentable sugars, also contain undesirable byproducts from the pretreatment process. These undesirable byproducts include, but are not limited to, lignin, furfural, HMF (hydroxymethylfurfural), and acetic acid.

[0093] Acetic acid, for example, acidifies yeast cytosol and requires the yeast to use ATP to pump protons out of the cell. This stresses the micro-organism and inhibits the production of ethanol. See, for example, Bellissimi E, et al., Effects of acetic acid on the kinetics of xylose fermentation by an engineered, xylose-isomerase-based Saccharomyces cerevisiae strain. FEMS Yeast Res. 2009 May; 9(3):358-64, the entirety of which is hereby incorporated by reference. The inhibitor effects of lignin are likewise well known. See, for example, Klinke HB, et al., Inhibition of ethanol-producing yeast and bacteria by degradation products produced during pre-treatment of biomass. Appl Microbiol Biotechnol. 2004 Nov; 66(1): 10-26, the entirety of which is hereby incorporated by reference.

[0094] Traditional approaches to minimizing these undesirable impurities in a C5 juice stream included, but were not limited to, optimization of pretreatment conditions, removal of some acetic acid and/or furfural through evaporation prior to fermentation, and engineering robust organisms capable of handling high concentrations of inhibitors. Despite these measures, it was still often necessary to run fermentations at concentrations of about 120 g/L to about 140 g/L, and in certain embodiments, at about 130 g/L for C5 juice streams. By way of contrast, conventional fermentation processes could be run at about 200 to about 300 g/L, depending upon the sugar source (e.g. sucrose). The significantly lower concentration required for C5 juice streams resulted in lower ethanol titers after fermentation and ultimately, higher production costs.

[0095] And, although additional makeup water could be added to the C5 juice stream, for example, to lower the concentrations of acetic acid to less than about 20 g/L, the concentration of dissolved lignin to less than about 70 g/L, and the combined concentration of furfural and HMF to less than about 1 g/L - the addition of make-up water only worsened the economics of the fermentation as downstream processing costs increased commensurate with the quantity of makeup water added. [0096] The present process, however, moots many of the issues associated with standalone hemicellulose sugar fermentation. More specifically, because the present process can be configured to produce both a primary juice stream, an optional secondary juice stream, and a C5-enriched secondary juice stream, the C5-enriched secondary juice stream can be diluted with the primary juice stream and/or the secondary juice stream to produce a combined juice stream that is enriched in hemicellulose sugars and sucrose (together "fermentable carbohydrates") but that contains significantly reduced concentrations of undesirable impurities due to the dilution resulting from combination. Alternatively, or in addition to any of the foregoing, molasses (resulting from the sugar refining process) can be added to provide additional fermentable sugars such as glucose and fructose. In certain embodiments, additional makeup water can be added to achieve the desired dilution. In other embodiments, water can be removed (under reduced pressure or otherwise) to obtain a combined juice stream having the correct constituent concentrations.

[0097] In certain embodiments, the primary juice stream can be combined with the C5- enriched secondary juice stream at a ratio of sucrose to hemicellulose sugar of from about 1 : 1 to about 100: 1 including all ranges and ratios therein. In particular embodiments, the ratio can be about 1 : 1, about 2: 1, about 3: 1, about 4: 1, about 5: 1, about 6: 1, about 7: 1, about 8: 1, about 9: 1, or about 10: 1, 20: 1, 30: 1, 40: 1, 50: 1 or 60: 1. In a particular embodiments, the ratio of ratio of sucrose to hemicellulose sugar can be about 6:1.

[0098] Combination of the primary and C5-enriched secondary juice streams can result in the combined juice stream having predetermined inhibitor and fermentable carbohydrate concentrations. For example, in certain embodiments, the combined juice stream can be formulated to contain less than about 1 g/L, less than about 0.5 g/L, less than about 0.2 g/L, less than about 0.1 g/L, less than about 0.01 g/L, less than about 0.001 g/L, or less than about 0.0001 g/L HMF and furfural combined. In particular embodiments, the combined juice stream can be formulated to have about 1 g/L HMF and furfural combined.

[0099] In certain embodiments, acetic acid concentration of the combined juice stream can be less than about 20 g/L, less than about 15 g/L, less than about 10 g/L, less than about 5 g/L, or less than about 1 g/L. In particular embodiments, the acetic acid concentration of the combined juice stream can be about 4 g/L. [0100] In certain embodiments lignin concentration of the combined juice stream can be less than about 70 g/L, less than about 50 g/L, less than about 30 g/L, less than about 25 g/L, less than about 20 g/L, less than about 18 g/L, less than about 16 g/L, or less than about 10 g/L. In particular embodiments, the lignin concentration in the combined juice stream can be about 16 g/L.

[0101] In certain embodiments, concentration of fermentable carbohydrates in the combined juice stream can range from about 140 to about 220 g/L, from about 150 g/L to about 210 g/L, from about 160 g/L to about 200 g/L, or from about 170 g/L to about 190 g/L. In certain embodiments, the combined concentration of hemicellulose sugars and sucrose is about 180 g/L.

[0102] In some embodiments, the concentration of fermentable carbohydrates can range from about 150 to about 250 g/L, from about 180 g/L to about 240 g/L, from about 190 g/L to about 230 g/L, or from about 200 g/L to about 220 g/L. In certain embodiments, the combined concentration of hemicellulose sugars and sucrose is about 210 g/L.

[0103] In some embodiments, the combined juice stream can comprise from about 140 to about 220 g/L fermentable carbohydrates and less than about 20 g/L acetic acid, less than about 15 g/L acetic acid, less than about 10 g/L acetic acid, less than about 5 g/L acetic acid, or less than about 1 g/L acetic acid; and lignin concentration of less than about 70 g/L, less than about 50 g/L, less than about 30 g/L, less than about 25 g/L, less than about 20 g/L, less than about 18 g/L, less than about 16 g/L, or less than about 10 g/L; and less than about 1 g/L, less than about 0.5 g/L, less than about 0.2 g/L, less than about 0.1 g/L, less than about 0.01 g/L, less than about 0.001 g/L, or less than about 0.0001 g/L HMF and/or furfural. In particular embodiments, the lignin concentration in the combined juice stream can be about 16 g/L, the acetic acid concentration of the combined juice stream can be about 4 g/L, and the furfural and HMF concentration can be less than about 0.1 g/L.

[0104] In particular embodiments, the combined juice stream comprises about 180 g/L fermentable carbohydrates wherein about 155 g/L is sucrose and about 25 g/L is hemicellulose sugars; about 4 g/L acetic acid, about 16 g/L lignin; and about less than about 0.1% furfural and HMF. In another embodiment, the combined juice stream comprises about 210 g/L fermentable carbohydrates wherein about 180 g/L is sucrose and about 30 g/L is hemicellulose sugars; about 4 g/L acetic acid, about 16 g/L lignin; and about less than about 0.1 g/L furfural and HMF.

Examples

[0105] The processes described herein are now further detailed with reference to the following examples. These examples are provided for the purpose of illustration only and the processes described herein should in no way be construed as being limited to these examples. Rather, the processes should be construed to encompass any and all variations which become evident as a result of the teaching provided herein.

[0106] Example 1: Cofermentation of a Representative Combined Juice Stream

[0107] Yeast strains M3799 (as described in PCT/US2013/000090) and wild type strain

M2390 - S. cerevisiae were grown overnight in shake flasks with yeast extract (10 g/L) and peptone (20 g/L) medium with 40 g/L sucrose as the sugar source (YPS media) at 35 °C and 220 rpm. The resulting cells were pelleted by centrifugation at 5000 rpm for 5 min in 250mL centrifuge bottles. Cells were then transferred to 50mL tubes in the quantities noted in Table 1 ("Yeast Cell Mass") and quantities of the remaining ingredients were added in the quantities shown in Table 1. Actual cell loading was 8% of total fermentation mass (equivalent to approximately 4.8 g/L dry cell weight). Final sugar concentrations loaded into the tubes were 155 g/L of sucrose and 25 g/L of xylose (bottles 1, 2, and 6), 180 g/L of sucrose (tubes 3, 7, and 8), or 180 g/L of xylose (tubes 4 and 5).

[0108] The tubes were sealed with pressure monitoring devices (Ankom). Samples were collected at 14 hours to check ending dry cell weight and to analyze the resulting solution via HPLC.

Table 1

Yeasl Cel l Yeast Penicil l in ( i Tola l

Tube Oil i W ilier Sucrose Xylose I Vnione

mass ( w ei extract d ηι ml . Mass

11111 Si rii i n ( » > (g) (g) <g>

Lini ni i (g) slock Mil l . ) (g)

1 & 2 M3799 17.75 3.875 0.625 2.0 0.25 0.5 0.023 25.00

3 M3799 17.75 4.5 0.00 2.0 0.25 0.5 0.023 25.00

4 & 5 M3799 17.75 0.00 4.5 2.0 0.25 0.5 0.023 25.00

6 M2390 17.75 3.875 0.625 2.0 0.25 0.5 0.023 25.00

[0109] As a control, wild type strain M2390 was used to ferment 180 g/L sucrose, and approximately 50 PSI of total pressure was accumulated in the system. See, Tubes 7 & 8 in Table 1. (Figure 8 - solid gray line and 4-pointed star). When engineered strain M3799 was used to ferment a mixture of sucrose (155 g/L) and xylose (25 g/L), the pressure resulting from the process was nearly equivalent to the control over the same period of time. See, Tubes 1 & 2 in Table 1. (Figure 8 - triangle and solid black line). These control results were nearly identical to the results observed for Tubes 1 and 2 indicating that virtually all of the xylose and sucrose in the combined juice stream in Tubes 1 and 2 was converted to ethanol.

[0110] When wild-type strain M2390 was used on the sucrose/xylose mixture (Tube 6;

Fig. 8 - crescent), the recorded pressure was about 70% of the control pressure. When xylose utilizing strain M3799 was given only sucrose (Tube 3; Fig. 8 - lightning bolt), the accumulated pressure was less than about 50%> of the pressure observed in the control. When strain M3799 was given all xylose (Tubes 4 & 5; Fig. 8 - 5-pointed star and circle) it was unable to ferment much sugar at all and only generated 10 to 15% of the pressure observed with the control, indicating that the presence of some sucrose was necessary for the fermentation process to proceed.

[0111] These results clearly show that an integrated approach of the type disclosed herein can produce a combined juice stream suitable for fermentation, providing significant advantages to ethanol producers.

[0112] Example 2 - Cofermentation of a Molasses-Derived Combined Juice Stream

[0113] Strain M2390 and an engineered strain M3799, both as described in Example 1, were each grown in a mixture of molasses and xylose. In the mixture, sugars from molasses (glucose, fructose, and sucrose) made up 86%> (w/w) of the mixture and xylose made up the remaining 14% (w/w). Target sugar loading in the fermentations was 150 g/L.

[0114] Cells of M2390 or M3799 were precultured in YPS media, as described in example 1, and were loaded at approximately 13% wet weight of cells (1.3 g wet cells per 10 g total fermentation mass) per total fermentation mass. Fermentations were set up in 30 mL sealed glass bottles (serum vials), vented with a 23 gauge needle and loaded with stocks of molasses (50% w/w dilution of starting molasses in water; total sucrose, glucose and fructose was 29% w/w in water after dilution), xylose (50%> w/w in water), and yeast extract and peptone (50 and 100 g/L in water respectively). The stocks were added along with cells (1.3 grams wet) to create mixtures of sugars as described above (150 g/L total sugars, with fractions coming from molasses or xylose) with yeast extract and peptone media stock diluted 1 in 5. Bottles were incubated at 35C and mixed at 150 RPM in a shaker. Samples were taken at 2, 4, and 8 hours and analyzed by HPLC for sugar and ethanol concentrations.

[0115] The fermentation results are shown in Figure 9 and include the quantity of ethanol produced at a given time and the concentration of a given sugar at a given time point. As is shown in the figure, M3799 is able to rapidly co-ferment xylose and sucrose, producing 22% more ethanol than the wild type strain in the same system.

[0116] Example 3 - (Prophetic) - Cofermentation Using M5401

[0117] M5401 (disclosed in PCT/US2013/000090), a yeast strain capable of fermenting hemicellulose sugars directly to ethanol, is used to ferment a combined juice stream, optionally including sucrose and other sugars from molasses. This fermentation is compared to a wild type strain that is not engineered to ferment hemicellulose sugars. The strains are each grown in mixtures where the fermentable material is a) all sucrose (derived from molasses, a primary juice stream, or a combination thereof); b) all hemicellulose sugars (derived from a C5-enriched juice stream); or c) 86 weight % sucrose and 14 weight % hemicellulose sugars (sourced as noted previously herein). Total sugar concentrations loaded into the fermenter are 170 g/L, including sucrose, glucose, fructose, and hemicellulose oligomers and monomers. Cells are loaded at 8 to 13% wet weight of cells per mass of the reaction. The prophetic results of this test are given in Table 2. Table 2

[0118] As is shown in Table 2, the wild type strain is able to ferment virtually all of the sucrose (>99%) into ethanol in the given time frame, producing about 80 g/L of ethanol in 8 hrs, corresponding to -92% theoretical yield (0.511 g ethanol/g sucrose fermented) on sucrose. However, the wild type strain is unable to ferment hemicellulose sugars. As a result, it produces no ethanol when subjected to hemicellulose sugars and only ferments sucrose when exposed to a mixture of hemicellulose sugars and sucrose.

[0119] By contrast, M5401 ferments sucrose and hemicellulose sugars present in the mixture. This fermentation produces 78.3 L of ethanol per gram of fermentable material, representing an 85% ethanol yield on the available hemicellulose sugars, and retaining the >90% ethanol yield on fermented sucrose. By way of distinction, when hemicellulose sugars are fermented alone with no sugar derived from molasses and/or the primary juice stream, only a 50% yield on available hemicellulose sugars is realized.

[0120] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.

[0121] The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. A process for preparing a C5 -enriched juice stream, the process comprising:

a. pretreating bagasse, cane trash, or a combination thereof to produce a C5 -enriched material; and

b. extracting the C5-enriched material to produce a C5-enriched juice stream.

2. The process according to claim 1 , wherein the pretreating comprises treating the bagasse with steam for about 5 to about 15 minutes at a temperature of from about 150 °C to about 200 °C.

3. The process of claim 1, wherein the extracting comprises milling the C5-enriched materials or passing the C5-enriched materials into a diffuser.

4. The process of claim 3, wherein the milling comprises subjecting the C5 -enriched material to at least one milling stage and washing the C5 -enriched material subjected to milling with imbibition water to produce the C5 -enriched juice stream.

5. The process of claim 4, wherein the at least one milling stage comprises two, three, four, five, or six milling stages.

6. The process of claim 5, wherein the at least one milling stage comprises four milling stages and wherein the C5-enriched materials are subjected to countercurrent washing.

7. The process of claim 3, wherein the extracting comprises passing the C5 -enriched material into a diffuser.

8. The process of claim 1, wherein the C5-enriched juice stream comprises sucrose and hemicellulose sugars.

9. The process of claim 8, wherein the C5-enriched juice stream comprises from about 1% to about 50% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

10. The process of claim 9, wherein the C5-enriched juice stream comprises from about 3% to about 33%) (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

11. The process of claim 9, wherein the C5-enriched juice stream comprises from about 1% to about 5%> (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

12. The process of claim 1, further comprising subjecting the C5-enriched juice stream or a stream derived from the C5 -enriched juice stream to co fermentation.

13. A process for preparing a C5 -enriched juice stream, the process comprising:

a. feeding sugarcane to a first milling stage to produce a primary juice stream and bagasse;

b. pretreating the bagasse produced by the first milling stage to produce a C5 -enriched material; and

c. extracting the C5-enriched material to produce a C5-enriched juice stream.

14. The process of claim 13, wherein extracting the C5 -enriched material to produce a C5- enriched juice stream comprises feeding the C5 -enriched material to a diffuser.

15. The process of claim 13, wherein extracting the C5 -enriched material to produce a C5- enriched juice stream comprises subjecting the C5-enriched material to at least one, at least two, at least three, at least four, at least five, or at least six additional milling stages.

16. The process of claim 13, further comprising combining the C5 -enriched juice stream with the primary juice stream.

17. The process of claim 14, wherein the C5-enriched juice stream and the primary juice stream are not combined.

18. A process for preparing a C5 -enriched juice stream, the process comprising:

b. feeding the bagasse to at least a second milling stage to produce a secondary juice stream and extracted bagasse;

c. pretreating the extracted bagasse to produce a C5-enriched material; and

d. extracting the C5-enriched material to produce a C5-enriched juice stream.

19. The process according to claim 18, further comprising combining the secondary juice stream and the C5-enriched juice stream to produce a combined juice stream.

20. The process according to claim 19, further comprising processing the combined juice stream to produce a juice stream suitable for cofermentation.

21. The process of claim 18, wherein feeding the bagasse to at least a second milling stage to produce a secondary juice stream and extracted bagasse comprises feeding the bagasse to at least one, at least two, at least three, at least four, or at least five milling stages.

22. The process of claim 20, further comprising cofermentmg the combined juice stream.

23. The process of claim 22, wherein the co fermenting comprises contacting the combined juice stream with a microorganism capable of fermenting xylose and sucrose.

24. The process of claim 23, wherein the microorganism is M3799 or M5401.

25. The process of claim 23, wherein the contacting is at a temperature of about 35 °C.

26. A C5 -enriched juice stream prepared by the process of: a. pretreating bagasse, cane trash, or a combination thereof to produce a C5 -enriched material; and

b. extracting the C5-enriched material to produce a C5-enriched juice stream.

27. The C5 -enriched juice stream prepared according to the process of claim 26, wherein the pretreating comprises treating the bagasse with steam for about 5 to about 15 minutes at a temperature of from about 150 °C to about 200 °C.

28. The C5 -enriched juice stream prepared according to the process of claim 26, wherein the extracting comprises milling the C5-enriched materials or passing the C5-enriched materials into a diffuser.

29. The C5 -enriched juice stream prepared according to the process of claim 26, wherein the milling comprises miling the C 5 -enriched material in at least one milling stage and washing the C5 -enriched material subjected to milling with imbibition water to produce the C5 -enriched juice stream.

30. The C5 -enriched juice stream prepared according to the process of claim 29, wherein the at least one milling stage comprises two, three, four, five, or six milling stages.

31. The C5 -enriched juice stream prepared according to the process of claim 30, wherein the at least one milling stage comprises 4 milling stages and wherein the C5 -enriched materials are subjected to countercurrent washing.

32. The C5 -enriched juice stream prepared according to the process of claim 28, wherein the extracting comprises passing the C5 -enriched material into a diffuser.

33. The C5 -enriched juice stream prepared according to the process of claim 26, wherein the C5-enriched juice stream comprises sucrose and hemicellulose sugars.

34. The C5 -enriched juice stream prepared according to the process of claim 33, wherein the C5-enriched juice stream comprises from about 1% to about 50% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

35. The C5 -enriched juice stream prepared according to the process of claim 34, wherein the C5-enriched juice stream comprises from about 3% to about 33% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

36. The C5 -enriched juice stream prepared according to the process of claim 34, wherein the C5-enriched juice stream comprises from about 1% to about 5% (w/w) hemicellulose sugars based on the total weight of fermentable carbohydrates present in the stream.

37. The C5-enriched juice stream prepared according to the process of claim 26, further comprising subjecting the C5 -enriched juice stream or a stream derived from the C5- enriched juice stream to cofermentation.

38. A sugar/ ethanol production plant comprising :

a. at least a first extractive stage for generating bagasse;

b. a pretreatment reactor for generating a C5 -enriched material, wherein the pretreatment reactor is adapted to receive the bagasse from the at least a first extractive stage and, optionally, cane trash;

c. at least a second extractive stage for generating a C5 -enriched juice stream, wherein the at least a second extractive stage is adapted to receive the C5-enriched material; and

d. a cofermentation reactor for fermenting the C5-enriched juice stream.

39. The sugar/ethanol production plant of claim 38, wherein the at least a first extractive stage is at least a first milling stage.

40. The sugar/ethanol production plant of claim 39, wherein the at least a second extractive stage is at least a second milling stage.

41. The sugar/ethanol production plant of claim 39, wherein the at least a second extractive stage is a diffuser.