DD212053A1 - PROCESS FOR OBTAINING ETHANOL - Google Patents

Abstract

The invention relates to a process for obtaining ethanol from fermentable carbohydrates by means of fermentation processes, which are carried out batchwise, semicontinuously, in two or more stages and with Hückueckfuehrung or -background. The aim of the invention is to achieve a high ethanol end concentration with good ethanol yield and long-lasting Gaeraktivitaet the amount of yeast used repeatedly from 20 to 100 g HTS / l without an unproductive aerobic Nichtgaerphase is undergo to activate the yeasts. This goal is achieved by means of a two- to multi-stage procedure, in which a short-term fermentation, with or without partial ventilation, alternates to activate the fermentation yeast with a long-term fermentation with a high sugar supply. Due to the relatively low sugar supply in the Kurzzeitgaerung sufficient activation of Gaerhefe is achieved on the one hand, on the other hand, the Gaerhefe for growth little time available, so that already formed in this stage ethanol in good yield and as a result of the overall process ethanol end concentrations of 90 to 100 g Ethanol / l and more can be achieved.

Description

The invention relates to a process for the production of fermentation ethanoi by means of yeasts from fermentable carbohydrates. The invention can be applied to discontinuous or semi-continuous fermentation processes which are carried out sterile or unstable with yeast retention or recirculation · It belongs in the IPK C 12 Έ 1/00.

Characteristic of the known technical solutions

The ethanolic fermentation is characterized by the product inhibition of the process. As ethanol concentration increases, fermentation yeast growth and ethanol production decrease. The growth and the ethanol formation come to a standstill at ethanol concentrations of 40 to 50 or over 80 g of ethanol / 1 completely.

As a result of ethanolic fermentation, the fermenting activity of yeast and its viability are negatively affected.

This can lead to complete death of the fermentation organisms, as was found at Etfaanolendkonzentrationen of about 130 g of ethanol / 1. (U.Y. Wang, F.M. Robinson, S.S. Lee, Biotechnol., Bioeng., Symp., 11, 555-65 (1981).) For this reason, conventional methods employ ethanol end concentrations of 70 to 85 g ethanol / l.

-3DE11932 * 052245

Yeast concentrations of less than 15 g of yeast dry matter (HTS) / l are preferably used, the fermentation times being relatively long, namely from 20 to 72 hours. Shorter fermentation times are achieved by the use of boiling yeast concentrates. reached. This is accounted for by a number of recent process developments employing yeast concentrations of 50 to 120 g HTS / 1. The use of these high yeast concentrations requires the provision of appropriate amounts of carbon substrates for cultivation, which are removed from ethanolic fermentation and burden the economy of ethanol production The newer process developments therefore concentrate on minimizing this expense. It reduces z * B by using the fermented yeast once cultivated several times. This is achieved either by the recirculation (DS 2917 411, DE 2261 238, DE 2903 273, AT 334 857) of the separated yeast content in the fermenter effluent or by yeast retention in the fermentor. Various technologies have been developed for yeast containment, for example B, retention by filtration with suitable membranes (DT 1517 300, J 54 132 291, GB 1406 506) or immobilization or fixation of the yeasts in or on suitable carrier materials (OH 489 601; DD-AS 126 842, J 53 128-072, J 53 118-584).

In all processes involving yeast retention or recirculation, it is important to maintain the fermentability and viability of the yeasts over a longer period of time. Thus, after the separation, the yeasts are subjected to an acid wash (OE-PS 334 857) and / or to an aerobic activation stage (GH 5,20,197, DE 2354 556, DE 2426 120, DE 2151 574, FR 2168 225) in order to regenerate their fermenting activity. All of these processes are usually associated with the disadvantage that during the regeneration of the yeast no or only negligible amounts of ethanol are formed.

ώ. J) -

Object of the invention

The aim of the invention is to develop a method in which normal-power fermentation yeasts are stimulated, instead of forming the usual 70 to 80 g ethanol / 1 ethanol end concentrations of 110 to 13Og ethanol / l. At the same time, the loss of fermentability and viability be kept low and activation or regeneration of the fermentation yeast with simultaneous ethanol formation - without a separate Hichtgärstufe - done.

Essence of the invention

The invention has for its object to find a suitable procedure in which both high ethanol concentrations are achieved and the Gäraktivität and viability is maintained long.

This is achieved according to the invention with the aid of a two- to multi-stage process with yeast return or retention. In yeast return processes, intermediate storage of the separated yeast material is often required. It has been found, however, that intermediate stored yeast material does not immediately exhibit its full fermentability.

The fermentation yeast initially begins to multiply, whereby less ethanol is formed from the fermentable sugar. "It is an activation of the fermentation yeast (activation phase), which can last over several fermentations (Figure 1). This activation phase is further characterized by a prolonged fermentation period. If the yeast is loaded in this phase by carbon substrate or ethanol concentrations of> 180 g reducing substance (RS) / l or> 90 g ethanol / 1, this leads to an increased decrease in the viability of the cells.

It has also been found that with the use of fresh yeast material initially also increased growth at the expense of ethanol formation takes place, however, with renewed use of the separated after completion of the first fermentation yeast material in a 2, fermentation process less yeast, but very good yields of ethanol were obtained.

The course of the 3rd and 4th fermentation with the same fermentation yeast corresponds to that of the 1st or 2nd fermentation. A fermentation stage with increased growth (activation phase) is followed by a fermentation with a higher ethanol yield as shown in the picture.

On the basis of the results shown in Figure 2, a two- to multi-stage process with Hückückführung or -haltung have been developed, with the help of which higher ethanol concentrations and high ethanol yields are achieved in long lasting fermentation activity of the repeatedly used yeast material.

This method consists of a short-time fermentation with a relatively low sugar supply of 140 to 170 g RS / 1 and a long-term fermentation with an exceptionally high sugar supply of 220 to 280 g RS / 1.

In this case, high yeast concentrations of 20 to 100 g HTS / 1 were used. The fermentation yeast is exposed in the 1, stage very gentle fermentation conditions. It is achieved sufficient activation of the yeast material.

Due to the selected favorable yeast-sugar ratio, the fermentation time is relatively short and the yeast growth is relatively low, so that ethanol is already formed in this step with good yield

After completion of the short-term fermentation, the separated fermentation yeast is used in the long-term fermentation. Due to the extraordinarily high supply of sugar, a high ethanol end concentration with good yield and a fermentation yeast with less fermentability are obtained. By reusing the fermentation yeast in a fermentation process whose fermentation conditions correspond to those of the first fermentation, sufficient activation of the yeast material is achieved that in a fermentation it can be re-exposed to the extreme fermentation conditions corresponding to the 2nd fermentation. "This change of fermentations with different final ethanol concentration can be continued until the proportion of dead yeast cells is 25 % . In this palium an aerobic regeneration of the fermentation yeast must take place.

It can be carried out according to the invention at the beginning, in the same fermentation reactor and as part of the activation fermentation and must take up about 1/3 of the fermentation time. With a higher content of dead cells than 35 % , fresh yeast material should be used.

Overall, it should be noted that the fermentation yeast despite the burden of long-term fermentation due to the previous and subsequent activation fermentation sufficient amounts of ethanol are formed.

As a result of the succession of fermentations with different final ethanol concentrations, average concentrations and yields of ethanol of 100 g ethanol / 1 and 0.47 g ethanol / g sugar, respectively, are achieved. In this procedure, one and the same yeast material can be used more often than in previously known terms. "The process is explained in more detail with the following example:

Example:

Sin stirred tank fermenter with a working volume of 4 1 was in four successive fermentations each with a solution of mineral nutrients, yeast extract and glucose fed and in the 1st fermentation with a fresh, in the further fermented with the fermented yeast of the species Saccaromyces cerevisiae. The permentor was equipped with a commercial measuring and Hegel technology for temperature control and pH control.

The discontinuous fermentations were carried out at a pH of 4.2 and a temperature of 33 ⁰ C.

The composition of the nutrient solution based on 1 g HTS was as follows:

76 mg K ₂₄

28 mg MgSO ₄ . 7H ₂ O

135 mg P as 85 % H ₃ PO ₄

0.88 mg ZnSO. 7 H _p 0

1.43 mg _{2 2}

0.16 mg of CuSO 4. , 5 H ₃ O

0.88 mg MnSO ₄ . 5 H ₃ O

150 mg of yeast extract

367 mg (SH ₄ ) ₂ SO ₄

The most important parameters and results of the fermentations are summarized in Table 1.

The glucose offered in the first fermentation was 180 g ES / 1. Yeast concentration was 33 g HTS / l. After 3 hours the first fermentation was over. The ethanol concentration at Yersucfasende was 80 g ethanol / 1 and the yeast concentration was 40 g HTS / 1. The yield of ethanol obtained was 0.44 g ethanol / g glucose, the proportion of living

Yeast end yeast cells corresponded to 98 % of the culture composition at the beginning of Yersucfas.

After completion of the first fermentation, the yeast was separated and reused after separation of the excess yeast in a second fermentation process in the same stirred tank reactor. The glucose offered was 240 g glucose / l, and after 5 hours the fermentation had ended. The ethanol concentration at the end of the test was 120 g ethanol / l and the yeast concentration 38 g HTS / 1. The yield of ethanol obtained was 0.5 g ethanol.

n_Qi / g__GJLjÄO.Qafi- ^ JThe proportion of living yeast cells was 88 56.

After purification of the two ethanol-containing aqueous phases from the two fermentations, a 10% strength aqueous ethanol solution was obtained as a result of the overall process and an average ethanol yield of 0.476 g Etbanal / g glucose was calculated

The separated yeast material was used again in the 3rd fermentation process. The glucose supply was 160 g glucose / kg, the fermentation time was 3 1/4 hours, and at the end of the experiment, with a living cell fraction of 87 %, 74 g ethanol / 1 were produced at an aspiration yield of 0.46 g ethanol / g glucose. • The 4th fermentation was carried out with 230 g glucose / 1. After 5 hours of fermentation time, 115 g of stanol / 1 were obtained with a yield of 0.5 g of ethanol / g of glucose.

The living cell content is 85 % *

The mixture of the two ethanol-containing aqueous phases of the 3rd and 4th fermentation gave an approximately 9.45% ethanol solution. The arithmetic mean of the Bthanolausbeuten the 3rd and 4th fermentation is 0.48 g of ethanol / g glucose.

Table Ij Parameters and results of the multi-stage batch process with yeast leavening with alternating changes of short (1st and 3rd stage) and long-term fermentations (2nd and 4th stages)

Glucose · Level offer

g RS / 1

Yeast concentration of yeast at the beginning at the end of different yeast content

at the end g HTS / 1 %

ethanol yield

Ethanolkonzentr "

g ethanol / g RS g ethanol / 1

fermentation period

1 180 33 40 7 98 2 240 33 38 VJL 88 1.2 3 160 33 36 3 87 4 230 33 37 4 85 3.4

0.44 0 80 3 0.5 120 5 0,476 100 0.46 0 74 3.25 0.5 115 5 0.48 94.5

Claims (1)

1 »A process for the production of ethanol by means of fermentation yeast from fermentable carbohydrates, characterized in that the batch or semi-continuous in a two- or multi-stage process with a yeast concentration of 20 to 100 g HTS / 1 reactor contents After a Karzzeitgärung of 2 to 10 hours with a Zackerangebot of 140 to 170 g RS / 1 reactor contents and after recycling of the separated yeast or after retention of the yeast in the reactor a long-term fermentation with a sugar supply of 220 to 280 g RS / 1 reactor contents follows which lasts twice to a multiple of the time of the short-term fermentation, and when the fermentation steps are repeated, is preferably aerated at a proportion of 20 to 25 % dead cells based on the total yeast at the beginning and as part of the short-term fermentation, the aeration up to one One third of the duration of carcass fermentation is · For this purpose, see drawings 1 Soap tables