WO2010087737A2

WO2010087737A2 - Process for production of organic solvents

Info

Publication number: WO2010087737A2
Application number: PCT/RU2009/000618
Authority: WO
Inventors: Evgeniy Rubenovich Davidov; Petr Sergeevich Kanygin; Oleg Anatolievich Frakin; Igor Vladimirovich Cheremnov
Original assignee: Limited Liability Company "Prof Business"
Priority date: 2009-01-29
Filing date: 2009-11-12
Publication date: 2010-08-05
Also published as: RU2009102853A; RU2405828C2; WO2010087737A3

Abstract

The present invention relates to a process for production of organic solvents, particularly acetone, butanol, ethanol using the anaerobic fermentation by butanol, acetone, and ethanol- producing bacteria. The process comprises saccharifying the pretreated plant material with enzymes which degrade or convert the material into soluble sugars, fermenting the sugars by butanol, acetone, ethanol producing bacteria in a fermentor at a nutrient medium, removing organic solvents and fermentation gases, recovering end product, wherein the saccharification and the fermentation are carried out in parallel, moreover an even rate is maintained for the saccharification and fermentation.

Description

Process for production of organic solvents

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a process for production of organic solvents, particularly acetone, butanol, ethanol using the anaerobic fermentation.

BACKGROUND OF THE INVENTION

Butanol fermentation, also called acetone butanol ethanol (ABE) fermentation is one of the oldest fermentation processes. Butanol is the most valuable of the produced solvents.

Butanol is an important industrial chemical and is currently used as solvency enhancer in the formation of nitrocellulose lacquers, synthetic resins; as a feedstock chemical in the plastics industry and as a food grade extractant in the food and pharmaceutical industry. As it turned out butanol has excellent fuel characteristics. Compared to the currently popular fuel additive ethanol, butanol is more miscible with gasoline and diesel fuel, has a lower vapor pressure, and is less miscible with water, qualities that make butanol a superior fuel extender than ethanol. Use of butanol as fuel will contribute to clean air by reducing smog-creation compounds, harmful emissions (carbon monoxide).

Currently butanol is produced chemically by either the oxo process starting from propylene (with H₂ and CO over rhodium catalyst or nickel-cobalt catalyst) or the aldol process starting from acetaldehyde.

The recent trend of using butanol as biofuel has revived research efforts aimed at obtaining liquid fuels by anaerobic fermentation.

Now the main directions of ABE process development are focused on metabolic engineering of Clostridium (US 2007259410, WO 2007050671, etc.), improvements in the process productivity and research of new techniques of solvent recovery (US 2005089979, US 5755967).

Traditionally the microbiological process for producing organic solvents from plant material comprises few stages that are performed separately and sequentially. Most processes start with a pretreatment, followed by an enzymatic or chemical hydrolysis (saccharification), a microorganism-based fermentation of the resulting sugars and a recovery of the organic solvents.

For example, WO2008025522 discloses a method of producing bioalcohol, in particular ethanol or butanol, from biomass, the method is carried out sequentially: the biomass is comminuted and saccharified with enzymes, insoluble components and/or non-fermentable sugars are separated off from the biomass, the remaining biomass is fed to a fermentation and the alcohol is obtained from the product of the fermentation. US 20070178569 discloses a method of making a fuel from biomass material, the method comprising the following separate stages: providing biomass material reduced in size; hydrolyzing the biomass material to provide a hydrolyzed material; combining the hydrolyzed biomass material with Clostridium phytofermentans cells in a medium; and fermenting the hydrolyzed material under conditions and for a time sufficient to produce a fuel.

In the light of the aforesaid there is interest in process for producing organic solvents wherein the saccharification and the fermentation are performed simultaneously, i.e. soluble sugars after saccharification are not accumulated but fermented as they are produced. It allows to optimize the process for producing organic solvents, reduce the operating time, make cheaper by removal of separate reactors and some operations, for example concentration and sterilization of soluble sugars before fermentation.

However there are few obstacles to perform such process. The problem is that the saccharification of the plant raw material and the fermentation of the obtained sugars proceed at the different conditions, temperature, pH. Also it should to be noted that Clostridia are very fastidious (Jones D.T. et al., Acetone-Butanol Fermentation Revisited, MICROBIOLOGICAL REVIEWS, Dec. 1986, Vol. 50, No. 4, p. 484-524).

There is a brief information that researchers at the US Agricultural Research Service (ARS) are refining an integrated method of producing cellulosic biobutanol from wheat straw (Ed./Green Car Congress (2008, October 17) Integrated SSFR Process Could Make Cellulosic Biobutanol More Competitive with Ethanol. [WWW document]. URL http://www.greencarcongress.com/2008/10/integrated-ssfr .html#more). Dilute acid pretreated wheat straw in a bioreactor is saccharified by a combination of enzymes and fermented by a culture of C. beijerinckii P260, which produces a combination of acetone, biobutanol and ethanol (ABE). However the reference does not disclose the details of this process, either the possibility of continuous mode.

The researchers indicated the drawback of the process. In early trial runs the pace of fermentation outran the pace of hydrolysis and small batches of additional sugar were added in the process. Also the pretreatment with dilute acid refers to the drawback because it causes known difficulties of process structure.

Summarizing the aforesaid, a need exists for an improved continuous process to produce organic solvents from non-edible renewable plant material, particularly forestry residues, wherein the saccharification and the fermentation are performed simultaneously, preferably in a single vessel. BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a process for production of organic solvents comprising:

-saccharifying the pretreated plant material with enzymes which degrade or convert the material into soluble sugars,

-fermenting the sugars by butanol, acetone, ethanol producing bacteria in a fermentor at a nutrient medium,

-removing organic solvents and fermentation gases, -recovering end product, wherein the saccharification and the fermentation are carried out in parallel, moreover an even rate is maintained for the saccharification and the fermentation.

In one embodiment, the saccharification and the fermentation are carried out in a single vessel. The sugar concentration and the concentration of solvents are monitored to maintain the even rate. The sugar concentration in the fermentor is maintained at between about 1.2-2.5%. The process is carried out at pH 4.2-5.0 and temperature 33-55 ºC. In one embodiment, plant raw material is wood chips, hi one embodiment, the wood chips are coniferous wood chips. In the case the process further comprises removal of pitch, wherein removal of pitch is carried out by extraction with organic solvents. Preferably enzyme complex is used for saccharification. The enzyme complex is matched to polysaccharide components of the raw plant material. In one embodiment, the culture liquid obtained by cultivation (growth) of fungi Penicillium verruculos is used as the enzyme complex. In one embodiment, butanol, acetone, ethanol producing bacteria is Clostridium acetobutylicum.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention the saccharification and the fermentation are performed in parallel. It is possible to perform the saccharification and the fermentation in the different bioreactors maintaining the claimed conditions, i.e. the saccharification is carried out in one vessel and the fermentolysate is then fermented in a second reactor. It is clear that in the continuous mode the saccharification and the fermentation are performed in parallel. However in the preferred embodiment the saccharification and the fermentation are carried out in a single vessel. The number of vessels is reduced resulting in capital cost savings. Furthermore, the presence of alcohol during saccharification reduces the likelihood of contamination, especially in continuous operations.

The sugar concentration and the concentration of solvents are monitored to maintain the even rate for the saccharification and the fermentation. The sugar concentration in the fermentor is maintained at between about 1.2-2.5%.

The saccharification and the fermentation are carried out at pH 4.2-5.0 and temperature 33-55 ºC.

Preferably enzyme complex is used for saccharification. The enzyme complex is matched to polysaccharide components of the raw plant material. In one embodiment, the culture liquid obtained by cultivation (growth) of fungi Penicillium verruculosum is used as the enzyme complex.

Butanol, acetone, ethanol producing bacteria includes species of Clostridium, including Clostridium beijerinckii and Clostridium acetobutylicum, as well as another bacteria known in the art.

In accordance with the present invention the pretreatment of the plant material includes the coarse milling and the fine milling. The coarse milling of the raw material is carried out in mills, preferably in ball-mills to particles ranging in size from 1 mm to 2 mm with simultaneous drying by air blowing. The operation gives option to dry the raw material and prepare it for the fine milling. The fine milling is carried out to particles ranging in size from 1 μm to 5 μm.

In accordance with the present invention plant material includes various agricultural residues (straws, hulls, stems, stalks); deciduous and coniferous woods. One of advantages of the present invention is processing of forestry residues, particularly wood chips. hi one preferred embodiment, the plant material is coniferous wood chips, hi this case the removal of pitch is preferable before the fine milling. More particularly, wood chips are subjected to a solvent extraction process, preferably with acetone or ethanol (plant material: solvent ratio is 1 :7 - 1 :10).

We have found that such pretreatment in combination with such enzyme complex provides an optimal rate of the saccharification, gives an option to digest the polysaccharides completely. Moreover the claimed process in comparison to the processes from the prior of art allows that the amount of sugar that comes into solution per time unit is approximate to the amount of sugar consumed by Clostridium.

Recovery of solvents is achieved through vacuum removal under reduced pressure when butanol concentration in the fermentor is approaching to toxic for producing bacteria.

The invention may be further understood by the following non-limiting examples.

Example 1

The wood powder with particle size of l-5μm is suspended in water and the complex of hydrolytic enzyme (cellulase, xylanase and/or mannanase, cellobiase) is added to the suspension in the ratio 2.5 g per 1 kg of the fined wood powder. The saccharification was allowed to proceed at 55 ºC, pH 5.5 and in 12 hours the process is completed. 45% of carbohydrates are in the solution and lignin is removed from the sugar solution by centrifugation.

Obtained 2.7% carbohydrate solution was sterilized and then transferred into a fermentor. Then the mixture was inoculated with inoculum of Clostridium acetobutylicum VKM B-2531D with density of 1-2 milliard/ml. The fermentation was allowed to proceed at 37 ºC, pH 3.8 for 48 hours.

After removal of the solvents and the fermentation gas under vacuum, the nutrient medium, containing 75 g of sugars is added per day with the pace of 100 ml per hour. One time in two days 28 g of yeast autolyzate is added into the fermentor. Productivity was 8 g/l/day. Solvent yield on sugars is 27-33%. Sugar yield on the used wood powder is 14-16%.

The ABE vapors were cooled in a condenser and in result solution, containing butanol, acetone and ethanol was obtained (ABE ratio was 10:88:2).

Example 2

In a four-liter fermentor containing the suspension (density lg/cm³) of the wood powder with particle size of l-5μm and water the complex of hydrolytic enzyme (cellulase, xylanase and/or mannanase, cellobiase) is added (ratio 2.5 g per 1 kg of the milled wood chips). The mixture was inoculated with inoculum of Clostridium beijerinckii KM MSU (Moscow State University) No 101 with density of 1-2 milliard/ml. The saccharification and fermentation were allowed to proceed in parallel at 37 ºC pH 4.2 for 48 hours. The sugar concentration is constant and is 2 g/1.

After removal of the solvents and the fermentation gases under vacuum, the nutrient medium, containing fresh suspension of the wood powder in water, enzyme complex is added with the pace of 100 ml per hour. One time in two days 28 g of yeast autolyzate is added into the fermentor. Productivity was 8 g/l/day. Solvent yield on sugars is 27-33%. Sugar yield on the used wood powder is 14-16%.

Therefore the continuous process for production of organic solvents from non-edible renewable plant material, particularly forestry residues, is disclosed in which the saccharification and the fermentation are performed simultaneously, preferably in a single vessel.

Claims

1. A process for production of organic solvents comprising:

-saccharifying the pretreated plant material with enzymes which degrade or convert the material kilo soluble sugars;

-fermenting the sugary by butanol, acetone, ethanol producing bacteria, in a fermentor at a nutrient medium,

-removing organic solvents and fermentation gases,

-recovering end product- wherein the aaccharification and the fermentation are carried out in parallel, moreover an even rate is maintained for the saecharification and fermentation.

2. The process of claim 1 wherein the aaccharification and the fermentation are carried out in a single vessel.

3. The process of claim 1 wherein the sugar concentration and the concentration of solvents arc monitored to maintain the even rate.

4. The process of claim 1 wherein the sugar concentration in the fermentor is maintained at between about 1.2-2.5%.

5. The process of claim 1 wherein the saceharifieation and the fermentation arc earned out at pH 4.2-5.0.

6. The process of claim 1 wherein the sacαharification and the fermentation are carried out at the temperature of 33-55 ºC.

7. The process of claim 1 wherein the plant material is wood chips,

8. The process of claim 6 wherein the wood chips arc coniferous wood chips.

9. The process of claim 7, further comprising extraction of pitch,

10. TIic process of claim 1 wherein an enzyme complex is used for the sacchari Hoation and the complex is matched to polysaccharide components of the plant material.

11. The process of claim 10 wherein the culture liquid obtained by cultivation of Pcnicillium verruculowm is used as the enzyme complex.

12. The process of claim 1 wherein said butanol, acetone, ethαnol producing bacteria, are Clostriduium acetobutylicum.