CA1211398A

CA1211398A - Process for treating starch or starch-containing raw materials

Info

Publication number: CA1211398A
Application number: CA000445187A
Authority: CA
Inventors: Karl Faltejsek; Vilim Cvitas; Reinhart Hanke; Bertalan Treso
Original assignee: Voestalpine AG
Current assignee: Voestalpine AG
Priority date: 1983-01-13
Filing date: 1984-01-12
Publication date: 1986-09-16
Also published as: ATA10983A; EP0114162B1; ZA8469B; DE3475411D1; EP0114162A2; EP0114162A3

Abstract

Abstract For treating starch or starch-containing raw materials, the starting material is subjected to a mechanical treatment, noting that the fraction rich in starch is, after having been wetted, thermally degraded by applying high temperatures, for example by applying saturated steam at 110 to 130°C. The thermally degraded starch fraction is cooled down to saccharification tempera-ture and saccharified by adding enzymes. For obtaining a higher reaction speed in the subsequent fermentation stage and for better energy utilization, the saccharified dispersion is cooled down to fermentation temperature or a slightly higher tempera-ture by dilution and the undissolved solid matter is separated, optionally after a flocculating stage, prior to the fermentation stage. This additional separation of solid matter immediately prior to the fermentation stage at temperatures exceeding the fermentation temperature or being already said fermentation temperature provides the possibility to immediately obtain a substrate of low con-tent in solid matter, in which substrate the fermentation can more rapidly proceed.

Description

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The present invention relates to a process for treating starch or starch-eontaining raw materials for 2r-ducing fermentable sugar solutions, in whieh process the raw materials are mechanically comminutedl dispersed in water, thermally degraded and in par-ticular gelatinized at temperatures above 100 C and subsequentl~ sacchari~ied~
in partieular enzymatieally saceharified.
Sueh a process is disclosed in EP-A 0 044 428 according to which the starch-containing material (for example corn, beets, cane) is separated by a mechanical treatmen-t (crushing, sieviny, sifting) in-tO
a fraction rich in stareh (s-torage tissue) and into a fraetion of low starch eonten-t (skins). Separation is effeeted by using the differing mechanical strength and the density of both types of tissue. The fraction of low s-tarch content can be further processed for ob-taining animal feeding produc~s. The fraction rich in starch is subsequently wetted thereby adjusting a water content of approxima~ely 50 percent and effecting a thermal degrada-tion. The thermal degradation of the cell tissue and of the staxch grains is effected at 110 to l30 C under the condition of saturated steam. The starch fraction thus treated is further diluted with water and enzymaticall~

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~2~L~3~3 saccharified a-t about 70 C. Saccharification is effec~ed within a m:lxing apparatus at a water content of the di~-persion of 65 to 80 percent. With the known processes, enzymes required for fermcnting -the s~bstrate were already added prior -to the step of thermal decJrada~ion and the dispersion obtained was immediately subjected to an alcoholic fermentation. It is a drawback of such a manner oE operation that in such a substrate the fermen-tation speed during the fermentation is prede-termined by the dilution phenomena and diEfusion phenomena so that there results a long fermentation time.
The present invention produces a fer-mentable sugar solution which can be fermented to obtain alcohol within a substantially shorter time interyal and this immediately subsequent to the preparatory treatment For solving this task the invention essentially consists in that the saccharified dispersion is cooled, in parti-cular by diluting down to fermentation temperature or a slightly higher temperature and in -that undissolved solid matter is separated, optionally after a flocculation treat-ment, pr:ior to the fermentation step. By separating a further portion of recoverable solid matter subsequent to the saccharification stage, a Eurther raw material for producing an~mal feeding products can be obtained if no 25 flocculatiol1 step has been performed. By the dilution step performed subsequent to the saccharification step the fermentation temperature of, for example, about 35 C

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required for the alcoholic fermentation can immediately be adjusted. Separation oE solid matter after the cooling step can be effected, for example, b~ centrifugation or filtration and optionally be ~ssis-ted by flocculatinq the solid matter. Thus, a solution practically not containing any solid matter is obtained for the subsequent alcoholic fermen-ta-tion, so that the fermentation process is not adversely affected by inert solid matter or adsorption phenomena.
The process according to the inventlon provides the possibility to circulate alon~ a closed circuit a major portion of the obtained solutions and au~iliary material if this process is combined with a subsequent fermentation process, thus obtaining a particularly high efficiency, The solid matter having been separated after the cooling step may, if desired together with solid matter from the mechanical comminution step and not being suitable for being saccharified, be supplied to an animal feeding production.
In par-ticular when producing a fermentation substra-te by loading yeast with the sugar solution produced according to the invention, a liquid containing further residual sugar is obtained prior to introducing the yeast sludge into the fermentation receptacle and it is just this liquid containing residual sugar whlch can be used in advantageous manner ~or diluting -the saccharified dis-persion and for cooling same down to fermentation. tempera-ture.

2~L~3~3l3 The solution se~arated from the yeast sludge has, as a rule, a sugar conten-t of 1 -to 8 percent by weight and can be used again in other staqes of -the process to produce in an advantageous manner e-thanol ~rom starch--contalning raw materlals. In ~his case the procedure can be such that the solu-tion having been separated from the yeast sludge prior to introducing same in-to the reaction chamber and containing residual sugar in an amount of preferably 1 to ~ percent and particular in an amount of 4 percent by weight is recycled to a preparatory stage for the sugar solution and is in particular used ~or diluting and cooling a gelatinized starch solution to be saccharified, for cooliny a saccharified solution down to fermentation temperature or for producing a starch-con-taining solution. The sugar solution having been separated from the yeast obtained by flotation and perhaps having already fermentation temperature can again be used for producing sugar solution in the stage for treating starch and in the stage for saccharifying ,starch. In particu~ar the mentioned solution can be used for wetting the starch material prior to the thermal conditioning stage~ It iS
equally possible to use the recycledsolution for diluting the thermall~ degraded starch. Such diluting is necessar~
for enzymatically saccharifying starch solutions, noting that simultaneously the material can be cooled from the temperatures for gelatinization and thermal conditioning~
respectively, which temperatures amount to approximatel~

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12~ C, down t.o approximately 70 C, so that there results a temperature whlch is particularly favouxable for the enzymatlc sacchar:iflcation. Likewise, -the solution contalning residual sugar can be used for cooling the sacchariEied clispersion down to ferme!ntatlon temperature or a temperature sliyhtly exceeding the fermentation tem-perature, so that a ermentation process performed immediately after such a process for treating starch or starch-containing raw materials can particularly economi-cally be performed with high heat recovery and, respectlve~~y,utilization of energy. When usin~ this solution for dosing the polyelectrolyte into the yeast sludge, the solution of -the polyelectrolyte can be heated to about fermerltation temperature so that also in this case mild ~5 fermentation conditions and thus a high fermentation efficiency can reliably be established.

The invention will be fu.rther illustrated with reference to a.schematic.flow diagram s~own in the accompanying drawing.
In the flow diagram, which is valid, for exampler for corn but is applicable without substantial modifi-cation also for other starch-containing raw materials, the mechanical pre-treatment is followed by a mixin~ step with water. The water required for producing this mixture can be recovered from a subsequent fermentation process~
noti.ng that only discharge losses must be made up with ~resh waterO The thermal degradation and, respectively~

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and gelatinization is subsequen-tly effected within an autoclave at approximately 120 C. Subsequen-t to this thermal degradation, a dilu-tion step and cooling s-tep is required for the saccharification s-tep, noting that 5 also in this case -there can advan-tageously be used a solution con-taining residual suyar and derived from sub-sequent process stages, ~or example a fermentation step.
Subsequent to the saccharification step, mixing with water and cooling is effected, whereupon undissolved solid matter is separated. The u~dissolved solid ma-tter can be supplied -to an animal feeding production together with the skins derived from the mechanical pre-treatment. The fil-trate obtained in this manner represents a substantially pure sugar solution which can immediately be subjected to fermentation.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for treating starch or starch-containing raw materials for producing fermentable sugar solutions, in which the raw materials are mechanically comminuted, dispersed in water, thermally degraded and sub-sequently, after a cooling step, saccharified, the saccharified dispersion being cooled down to fermentation temperature or a slightly higher temperature and undissolved solid matter being separated prior to the fermentation step.

2. A process according to claim 1, in which the raw material is thermally degraded by being gelatinized at a temperature above 100°C.

3. A process according to claim 1, in which the saccharification is enzymatic.

4. A process according to claim 1, 2 or 3, in which the saccharified dispersion is cooled by dilution.

5. A process according to claim 1, 2 or 3, in which the separation of the undissolved matter is effected after a flocculation treatment.

6. A process according to claim 1, in which the separated solid matter is supplied to animal feeding pro-duction.

7. A process according to claim 6, in which the separated solid matter is supplied together with solid matter from the mechanical treatment which is unsuitable for saccharification.

8. A process according to claim 1, in which the fermentation substrate is yeast loaded with sugar, the solution separated from the yeast sludge prior to intro-ducing same into the reaction chamber and containing resi-dual sugar in an amount of 1 to 8 percent by weight is re-cycled into a preparatory stage for the sugar solution and is used for diluting and cooling a gelatinized starch solu-tion to be saccharified solution down to fermentation tem-perature or for producing starch-containing solutions.