WO1987004465A1

WO1987004465A1 - Process for the fermentation of starch containing materials

Info

Publication number: WO1987004465A1
Application number: PCT/SE1987/000023
Authority: WO
Inventors: Ingemar Bjurenvall; Ernst Conrad
Original assignee: Ingemar Bjurenvall; Ernst Conrad
Priority date: 1986-01-21
Filing date: 1987-01-20
Publication date: 1987-07-30
Also published as: DK489687D0; SE453922B; SE8600253L; EP0257045A1; SE8600253D0; DK489687A; AU6899687A

Abstract

Process for the fermentation of starch containing material derived from cereals in order to produce alcohols, preferably ethanol, whereby the cereal starch is presaccharified by using alpha-amylase to a low dextrose equivalent value, whereupon one adds simultaneously amyloglucosidase and a suitable yeast culture for the fermentation of ethanol and carries out a simultaneous hydrolysis and fermentation to ethanol at 35-37°C.

Description

PROCESS FOR THE FERMENTATION OF STARCH CONTAINING MATERIALS. DESCRIPTION Technical field

The present invention relates to a process for the fermenta¬ tion of starch containing material derived from cereals for the production of alcohols, preferably ethanol.

The object of the present invention is to obatin a possibility to saccharify and ferment starch from cereals in a simple and rational way to alcohols, preferably ethanol, with a simulta¬ neous high yield of alcohols, preferably ethanol.

Background of the invention.

At industrail production of ethanol from cereals the starch contents of the cereal grains are primarily saccharified, af¬ ter an elimination of bran and gluten, to yield a high dex¬ trose equivalent, typically 95-97 DE; previously by an acid hydrolysis of the starch contents, today by an enzymatic hyd¬ rolysis by using amyloglucosidase of a gelatinized starch hav- ing been presaccharified by the action of amylase, whereupon the completely saccharified starch is fermented by adding a suitable yeast culture, to yield ethanol at 37 C during 48 hrs .

When the carbon dioxide generation has stopped, which occurs due to the fermentation the mash is distilled to obtain a cru¬ de alcohol, which is then subject to a fractionated distilla¬ tion to give 96% ethanol, or another suitable strength. A 100% yield of ethanol per 100 kg of starch shall be 57 kg of etha- nol according to the formulae:

^C6^H10°5 ^{+ H}2° --* ^C6^H12°6 100 kg 11 kg 111 kg

^C ₆ ^H ₁₂°6 ^{"" 2C} ₂ ^H5^{0H +} - ^C02 111 kg 57 kg 54 kg Description of the present invention

It has now surprisingly been shown possible to be able to eli¬ inate these two steps, viz. saccharification and fermentation and carry them out as one step only, whereby it, also surpris- ingly, has shown possible to obtain a considerably higher ield of ethanol than was previously known, whereby the inven¬ tion is characterized in that cereal starch is presaccharified by using amylase to a dextrose equivalent value of 10-15, whereupon amyloglucosidase and a yeast culture for the fer- mentation to ethanol are added; and a fermentation to ethanol is carried out at 35-37 C, whereby the yeast culture is added in such an amount that complete fermentation of the starch content is obtained.

Further characteristics are evident from the accompanying clai s.

By means of the present invention it is obtained, as mentioned above, a high ethanol ield, as well as one obta ns that the amount of am loglucosidase added can be restricted to a mini¬ mum as the inactivation of amyloglucosidase due to heat is restricted, which further increases the yield of the process in economical terms.

In a common two stage process of above pH of the presacchari¬ fied starch is adjusted by adding an acid to reach optimal conditions for the saccharification and the yeast culture. pH is thereby generally 4.5.

It has now turned out that such pH adjustment is not necessary in the process of the present invention as pH is selfadjusted in the saccharified starch solution to an optimal pH.

It has further turned out that the dextrose equivalent value increases to 40-45 DE by means of the am loglucosidase hydro¬ lysis, but ill then become stable at this level during the whole fermentation as the yeast fungus immediately ferment the glucose formed. The invention will be described more in detail in the follow¬ ing by way of some examples.

Example 1 800 g of crushed wheat (15.5% H₂0) were added to 3000 ml of water as well as 0.5 g of ^Q£-amylase (N0V0 Thermamyl). This slurry was heated to opti ma I o6-am lase hydrolysis to 95 C to obtain ge lat i ni zat on and presacchari fi cati on to a DE-value of 10-12, whereupon the slurry was subject to autoc lavat i on at 130 C to provide enzyme deactivation. The slurry was then cooled to 35 C and transferred to a fermentation flask. pH was hereby 6.5. Then 50 g of baker's yeast and 2 g of amylo¬ glucosidase were added. The fermentation flask with its slurry contents as then placed in a heating cabinet having constant temperature adjustment facilities at 35 C, whereby there was obtained a very strong fermentation. The pH of the slurry the¬ reby fell rapidly to pH 4.5, while simultaneously increasing the dextrose equivalent value to 40-45 %, which value was stable during the whole fermentat on. CO_?-release was accomp- lished after 24 hrs.

The mash obtained was then distilled to obtain a crude ethan¬ ol, comprising 33% per volume of ethanol. The direct yield was 1000 mis of 33% ethanol, which means 412 mis of 100% ethanol per kg of wheat.

Example A (Comparative).

At a conventional production of ethanol in an industry start¬ ng from winter wheat (15% H_0, 60% of starch) about 0.3 kg of 100% ethanol (percent by weight) are obtained per kg of wheat, which means 0.39 I of 100% ethanol (percent by volume). Theoretically 60 kg of starch shall give 33.6 kg ethanol. Yield normally 90%.

Example B (Comparative). 8 80000 gg ooff ccrruusshheedd wwhheeaatt ((15.5% H₂0) and 0.5 g of -amylase (N0V0 Thermamyl) were added to 3000 ml of water. The slurry was heated 95°C and was then autoclaved at 130 C for enzyme deactivation, i.e., all n accordance with Example 1 above. pH was then adjusted to 4.5 from 6.5 by adding HCl. 2 g of amyloglucosidase were added, whereupon the enzyme was allowed ttoo aacctt ffoorr 2244 hhrrss aatt 6 655°CC ttoo ggiiv' e a complete saccharification, i.e., to DE 96 in the solution.

The slurry was then cooled to 35 C and 50 g of yeast were add¬ ed and was allowed to ferment in a heating cabinet at 35 C for 24 hrs, when the C0_-release had ceased.

The mash obtained was then distilled which yielded 1000 ml of a distillate comprising 26.4% by volume of ethanol. The yield was thus 330 mis of 100% ethanol per kg of wheat.

As evident from above a better yield was obtained using the process of the present invention, Example 1, than using a con¬ ventional 2-stage ethanol production. Example B.

The amount of amyloglucosidase can be reduced considerably in the present process, as it is only deactivated to a small extent at 35 C .

Thus it is possible to use 0.5 g of amyloglucosidase per kg crushed wheat, however, more preferably 1.0 g of amyloglucosi¬ dase per kg.

In a modern conventional industrial production of ethanol from winter wheat bran is normally sieved off first, whereupon glu- ten is eliminated from the starch in hydro cyclones. The starch is saccharified and is then fermented in the way de¬ scribed above, whereupon gluten is washed and dried.

In the present process the whole contents of the grain can be present during the whole process, including the distilla¬ tion, whereby the distillate residue of bran and gluten can be used as a foodstuff or feedstuff additive after having been washed and dried. The present invention has been described above with reference to the use of wheat, but of course, any other cereal can be used, as rye, oat, barley, ryewheat, maize, rice, sorghum, and others. The total yield of ethanol is thereby dependent on the starch contents but the high yield compared with con¬ ventional 2-stage process is obtained in all cases. However, it seems to be less pronounced when using rice and maize.

Claims

CLAIMS.

1. A process for the fermentation of starch containing mate¬ rial derived from cereals for the production of alcohols, pre¬ ferably ethanol, characterized in that the cereal starch is presaccharified by usi ng oi-amy Lase to a dextrose equivalent value of 10-15, whereupon one adds am loglucosidase and a yeast culture intended for the alcohol wanted for the fermen¬ tation and carries out a fermentation to alcohol at 35-37 C, whereby the yeast culture is added in such an amount that a complete fermentation of the starch present is obtained.

2. A process according to claim 1, characterized in that the cereal starch is present in the form of whole and/or crushed cereal grains which in a concentration of 20-30% by weight of grain material in an aqueous solution is provided with ^amylase .

3. A process according to claim 2, characterized in that 0.4-0,8 g cC-amylase is added per kg of dry substance of grain material.

4. A process according to claim 1, characterized in that at least 0.5 g of amyloglucosidase is added per kg of dry sub¬ stance of grain material, preferably 1.0 g of amyloglucosi- dase.

5. A process according to claim 1, character zed in that the dextrose equivalent value during the amyloglucosidase hydroly¬ sis is kept at 40-45.

6. A process according to claims 1 and 3, characterized in that the presaccharification is carried out at a temperature of 60-95°C, preferably 90-95°C for a time period of at least 5 mi n .