Note: Descriptions are shown in the official language in which they were submitted.
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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~
f'~
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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
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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.
