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Patent 1125200 Summary

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Claims and Abstract availability

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(12) Patent: (11) CA 1125200
(21) Application Number: 327750
(54) English Title: METHOD AND APPARATUS FOR MAINTAINING THE ACTIVITY OF YEAST FERMENTATION
(54) French Title: APPAREIL ET METHODE POUR CONSERVER A LA LEVURE SES PROPRIETES
Status: Expired
Bibliographic Data
(52) Canadian Patent Classification (CPC):
  • 195/141
  • 195/4
(51) International Patent Classification (IPC):
  • C12G 3/02 (2006.01)
  • C12M 1/04 (2006.01)
  • C12M 1/08 (2006.01)
  • C12P 7/06 (2006.01)
(72) Inventors :
  • MEYRATH, JOSEPH (Austria)
(73) Owners :
  • WAAGNER-BIRO AKTIENGESELLSCHAFT (Not Available)
(71) Applicants :
(74) Agent: SWABEY OGILVY RENAULT
(74) Associate agent:
(45) Issued: 1982-06-08
(22) Filed Date: 1979-05-16
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data:
Application No. Country/Territory Date
A 3665/78 Austria 1978-05-19

Abstracts

English Abstract



ABSTRACT OF THE DISCLOSURE
A method and apparatus are provided for maintaining the
activity of yeast in a continuous fermentation of sugar-contain-
ing mash to alcohol. In the continuous fermentation process
fresh mash is continuously added and alcoholic solution contain-
ing yeast is continuously drawn off. This solution is permitted
to settle. At least a portion of the settled yeast is returned
to the fermentation process while the non-settled or non-flocculated
yeast cells and bacteria are drawn off along the alcohol-
containing solution. This results in considerable lowering of
the danger of infection from the bacteria as well as increase
in concentration of yeast in the fermenter and shortening of
the duration of time of the mash in the fermenter, thus increasing
productivity. The apparatus for effecting this process comprises
a fermentation vat and a yeast sedimentation container, with
conduit from the fermentation vat to the sedimentation container
of fermented mash with return conduit for settled yeast and a
conduit our of the settling stage of the alcoholic solution
containing non-settled yeast and bacteria.


Claims

Note: Claims are shown in the official language in which they were submitted.


The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. Method for the yeast fermentation of sugar-containing
mash to alcohol, which comprises subjecting a yeast and sugar-
containing mash to fermentation to produce an alcohol-containing
solution, withdrawing the alochol-containing solution, which also
contains yeast, from the fermenting mash, permitting the thus
withdrawn alcohol-containing solution to settle, whereby flocculated
yeast settles while non-flocculated yeast and bacteria remains
suspended, withdrawing the settled yeast which is substantially
free of the suspended bacteria, and reintroducing the same to the
fermenting mash.


2. Method according to claim 1 wherein the withdrawing of
the alcohol-containing solution, the settling of the withdrawn
alcohol-containing solution, the withdrawing of the settled yeast
and the reintroducing of the same into the fermentation stage are
effected continuously.
3. Method according to claim 2 wherein the settled yeast
is reintroduced into the fermenting mash along with fresh mash.


4. Method according to claim 3 wherein the withdrawn
settled yeast is homogenized prior to being reintroduced into
the fermenting mash.

13




5. Method according to claim 2 wherein the fermenting
mash contains up to 15% of the yeast required for the fermentation
of the mash and wherein the time of settling of the yeast from
the withdrawn alcohol-containing solution is up to one half the
time that the yeast remains in the fermenting mash.


6. Method according to claim 5 wherein the settled yeast
is reintroduced into the fermenting mash in dosed amounts.


7. Method according to claim 2 wherein the mash fermentation
is effected in successive passages through a plurality of
fermentation vats and wherein fermented mash from each fermentation
vat is subjected to settling.


8. Method according to claim 2 wherein a portion of the
settled yeast is removed from the system.


9. Method according to claim 2 wherein the withdrawn
alcohol-containing solution which also contains yeast is degassed
prior to settling.


10. Method according to claim 9 wherein the degassing is
effected to a concentration of alcohol of not more than 5% by
volume.
11. Method according to claim 1 wherein oxygen in the form
of air, pure oxygen or oxygen enriched gases is added to the
fermenting mash.

14



12. Method according to claim 7 wherein oxygen in the
form of pure oxygen, air or oxygen-enriched gases is introduced
into the fermenting mash in each fermenting vat.


13. Method according to claim 1 wherein the hydrogen ion
cencentration of the fermenting yeast is maintained at a pH
of less than 6.
14. Method according to claim 13 wherein the pH is 5.4.
15. Method according to claim 2 wherein the settling
stage is subjected to an eddy current to accelerate the aggrega-
tion of the yeast cells.


16. Apparatus for continuous yeast fermentation of
sugar-containing mash to alcohol, comprising at least one
fermentation vat in which yeast and sugar-containing mash
is subjected to fermentation to produce an alcohol-containing
solution; at least one settler in which alcohol-containing
solution containing yeast is subjected to settling whereby
flocculated yeast settles while non-flocculated yeast and
bacteria remains suspended; first conduit means for withdrawing
alcohol-containing solution from said fermentation vat and
introducing the same into the settler; and second conduit means
for withdrawing settled yeast from the settler and reintroducing
the same into the fermentation vat.



17. Apparatus according to claim 16 wherein said fermenta-
tion vat comprises a cylindrical reactor within which is located
a cylindrical, concentrically arranged tube which acts as a
riser for gases introduced into the reactor and which separates
rising current from falling current in the reactor.

16

Description

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


~2S~



It is well known that yeast cells, particularly of the
genus saccharomyces, break down sugar into ethyl alcohol and
carbon dioxide. This process is known as alcoholic fermentation
and results in the production of an ethyl alcohol-containing
solution ~ith about ~/O b~ volume of alcohol, depending on the
sugar content of the mash. In this process it is important to
inhibit the development of microorganisms other than the yeast,
such as for exam~le lactic acid ~acteria.
In normal alcoholic fermentation, the growth of yeast is
rather slow so that the fermentation takes a relatively long time.
In raw materials with a low nutrient content, such as spent sulfite
liquor or cellulose hydrolysate, the fermentation time is even
longer.
In order to reduce this inconvenience, in the prior art a
centrifuge has been arranged behind the fermentation stage in order
to separa~e the yeast after which the separated yeast cream was
used to inocculate fresh mash. However, since yeast cells have
only a slightly higher specific gravity than water, the centrifuge
required very high speed with consequent costly operationO ~Another
disadvantage of this method is that the yeast which is returned
to f~sh mash carries with it bacteria which multiply rapidly in
:
the fresh mash so that the fermentation product was severely
damaged thereby. In order to eliminate this disadvantage, the
outflowing yeast cream has in the past been subjected to treatment
with mineral acids. This treatment also carried ~ith it considerable
disadvantages.




,
.
,

~L25Z~


Generally speaking, in accordance with this invention
mash is subjected to fermentation with yeast, produced alcoholic
solution containing yeast is withdrawn and introduced into a
settler wherein some of the yeast flocculat~sand settles while
other yeast and also bacteria remain suspended in the solution,
the settled yeast is continuously reintroduced into the
fermentation stage along with fresh mash and the alcoholic
solution containing non-settled yeast and bacteria is continuously
withdrawn. This results in considerable reduction in the danger
of infection from bacteria with simultaneously increase of yeast
concentration in the fermenter resulting in shortening of the
time of duration of the mash in the fermenter and increase
in the productivity. The process is particularly advantageous
for the industrial production of alcohol, for example for the
alcohol addition to gasoline.
It is accordingly a primary object of the present invention
to p~ovide for a continuous alcohol production with increased
alcoholic content of the produced solution without undesired
bacteria being introduced into the high nutrient low alcohol mash~
,
It is a further object of the present invention to provide
a method for fermentation of sugar-contalning mash to alcohol
wherein the speed of fermentatlon is increased with c~nseguent
increase in production.

::
,




,

~252~1~


It is yet another object of the present invention to
provide apparatus for effecting the method of this invention.
With the above and other objects in view, the method
of the present invention mainly comprises subjecting a yeast-
containing mash to fermentation to produce an alcohol-containing
solution, continuously withdrawing the alcohol-containing
solution which also contains yeast and introducing the same into
a settler and permitting it to settle whereby flocculated yeast
settles to the bottom while other yeast and bacteria remain in
the liquid, withdrawing the settled yeast and reintroducing the
same with fresh mash into the fermenter, and withdrawing the
alcohol-containing solution with unsettled yeast and bacteria
from the settler.
In accordance with a preferred embodiment of the in-
vention the settled yeast is returned ln dosed amounts in
homogenized state into the ermentation stage so that the
fermentation stage contains at most 15~/o of the yeast necessary
for fermenting of the mash during the time of duration in the
fermenter, with the duration of time of the withdrawn alcoholic
~olution in the settler being not more than one half the time

of stay of the mash in the fermenter.




Por a fuller understanding of the invention,~reference
is had to the following descrlptlon taken in connection with
the accompanying drawings, in which:




_3

~!252~


FIG. 1 diagrammetically illustrates the carrying out of
the process of the present invention;
FIG. 2 diagrammetically illustrates a simplified ~ermentation
stage of the overall processi
FIG. 3 diagrammetically illustrates a variant for the
fermentation stage;
FIG. 4 diagrammetically illustrates a multi-stage process
similar to that of FIG. l;
FIG. 5 shows a variant of a multi-stage process of FIG. 4;
and
FIG. 6 diagrammatically illustrates a pilot plant.




Referring now to FIG. 1, this diagrammatically shows a process
for the production of ethyl alcohol solution from sugar-containing
mash. The mas~ is introduced through conduit 9 into a fermentation
stage 1 where the mash is fermented. The requirèd air is supplied
to the mash and fermentation vat through pipe 8. In order to avoid clump-
in~ o the yeast cells, a storing means, such as stirrer 10, is
provided for agitating the ma~h
The fermented liquor is discharged from the fermentation stage
~0 1 through conduit 11 into a settling tank or degasifier 12. This
is designed as a simple settllng tank or vacuum degasifier so that
the yeast sedimentation vat 2 only receives the degassed, fermented
mash. The sedimentation vat or settler 2 consists of two stages.

,..

--4--

.

2~


Conduit 3 leads from the first stage of settler 5 into the fermenta-
tion stage 1 for the r~turn of the yeast cream. The introduction
of the yeast cream and dosing thereof is effected by pump 13, which
also homogenizes the yeast cream. The pressure pipe to pump 13
can be fitted directly into the fermentation stage 1 or into the
feed conduit 9 through which the fresh mash is introduced.
Another conduit 14 leads from the settler 5 to a second
settler 5' which is designed as a thickener for the yeast cream.
The thickened yeast cream is liberated in washer 15 of alcoholic
impurities and ed in purified sta~e to other settlers 6 and 6'.
The liquid discharge 16 from settlers 5 and 5' contains the desired
alcoholic solution and is directed to the distillation plant
(not shown).
The washed alcohol from the yeast crop is used for the
production of new mash. Stirrers 7 and 7' are provided in settlers
5 and 5', respectively, for agglomerating the yeast. Any sugar-
containing solution, e.g. diluted molasses, can be used as mash,
even cellulose-containing waste waters or spent sulfite liquor can
be used.
FIG. 2 shows in simplified representation a fermentation
stage 1 as the first stage of a sedimentation plant 2. Fermentation
stage 1 consists substantially of a cylindrical vat 17 provided
with a tubular fitting 4 in which a feed pipe 18 is arranged. At
the bottom of vat 17 there is connected a circulation pipe 19 through
'
which a practically gas ~ree mash is ~ucked in through p~mp 20




--5--


,
. .

~25~


whose pressure pipe 21 leads into a nozzle 22 in which pipe 18
is connected. When li~uid is supplied through pipe 21, a vacuum
is proauced in the area of narrowest cross section of nozzle 22,
which is used to suck in gas, such as air, pure oxygen, oxygen-
enriched air or fermentation gas, so that the mash flowing through
nozzle 22 carries along with it the gas in finely divided bubbles
and mixes the same at the outlet of feed pipe 18 with the contents
of the fermentation stage.
The gas, which is not soluble in the mash, bubbles in
the tubular fitting 4 causing an upward flow therein, thus pre-
venting clumping of the yeast. The upward flow in chamber 14
causes a downward flow in the outer tubular chamber 23, so that
fresh mash is fed to tubular chamber 4, and a circulating flow
is effected. At the upper end of the vat 17 there is provided
a conical fitting whose outer chamber 24 is designed as a steady-
ing zone, while the interior chamber 25 represents the degassina
chan~er. In the steadying zone, the yeast grows undisturbed and
finally flocculates so that the yeast content of the discharge
from the fermentation stage 1 is increased.
Outlet 11 leads to the settler 5 from which pipe 3 returns
the yeast cream to the fermenting stage 1 while pipe 14 branches
; off therefrom. The homogeniæation of the returned yeast cream
is effected by means of pumps 13 and 20, respectively and by the
intensive flow in feed pipe 18. The introduction of fresh mash is
effected either into the clr~ulation condult 19 or in the connecting


-6-

.


-

~Z~i2~3~

a-ea of circulation conduit 19 to vat 17 at the region of the
outlet of the opening of conduit 18.

FIG. 3 shows another design of a fermentation stage 1 where
the air necessary for the accelerated fermentation is injected
close to the bottom of vat 17 inside the tubular cha~ber 4, so
that here too the flow described in FIG. 2 is obtained. In
contrast to FIG. 2, the returned yeast cream is introduced through
pipe 3 by means of pump 13 directly in homogenized form into vat
17. The outgoing air is removed as shown by arrows 26.

In the embodiments of FIGS. 2 and 3, the individual
settlers5 and 5' have a much larger volume than fermentation stage l,
so that even in a multi-stage sedimentation plant a volumetric
ratio of at most l:l is achieved. This is a great advantage over
known embodiments of yeast separating plants since the volume
of the settlers represents here a multiple of the fermentation
vat.
FIGS. 4 and 5 show multi-stage fermentation processes.
In FIG. 4, a two stage fermentation process is shown, wherein
settling stage 2 and 2', respectively is assigned to each fermenta-


tion stage l and l', and wherein return pipes 3 and 3', areprovided respectively for the yeast cream, leading from each
sedimentation stage into the feed pipe of the preceding fermenta-
tion stage l and l', respectively. The excess yeast cream is
removed through pipes 14 and 14', respectively and fed to a
productiDn plant similar to FIG. l. In order to o~tain a




--7--

`~

52~

uniformly high ethylene alcoh~ content in overflow 11', fresh
mash is supplied to each fermentation stage 1, 1' through pipes
9, 9'. This is particularly important in multi-stage plants
where more than two stages are used. In these plants the mash
can be produced, for example, in the first stage from molasses,
while pure sugar solutions are introduced through feed pipes
9, 9', so that the maximum alcohol content is not limited
by the rising impurities from the molasses.
FIG. 5 shows a three stage fermentation plant with the
individual stage being designated 1, 1' and 1", re~pectively.
These stages are provided with only a single common settler 2,
in contrast to FIG 4, from which the yeast cream is returned
through pipes 3, 3' and 3". For the exact dosing of the
returned amounts of yeast cream pumps 13, 13' and 13" are pro-
vided. In this embodiment too, fresh mash is supplied to each
fermentation stage through pipes 9, 9' and 9", and the
fermentation stages 1' and 1" also receives the discharge from
the preceding fermentation stages 1 and 1' respectively.
FIG. 6 shows the arrangement of a pilot plant where the
fermentation vat of fermentation stage 1 is provided with a
" separate ventilation system 22, 90 that a low velocity of flow
is obtained in the fermentation vat, which permits floccular
settling of the yeast in the upper region of the fermentation vat.
The yeast-enriched mash is fed through p1pe 11 to thickener 12,
which may be a centrifugal thickener, designed as a degasifier,
,,

~5~


as soon as a pxedetermined alcohol concentration has been obtained,
and the waste gas escapes in the ~rection of arrow 26'. The de-
gased mash is fed to settler 2 in ~ich the yeast settles to the
bottom of the funnel shaped settler and is returned by way of
dosing pump 13 into the fermentation vat. The excess yeast ob-
tained is separated through pipe 14. The fermented mash which is
freed of the settled yeast is removed through pipe 16. The use
of the settler results in only flocculated yeast being returned
to the fermentatinn vat while the non-flocculating yeast and
bacteria are removed with the alcoholic mash and fed to the
distillery. This results in a reduction of the risk of infection
in fermentation stage 1 so that the alcohol produced is of high
purity.
In tests which are carried out, the fermentation stage
was charged with 12 1 molasses mash up to the overflow limit.
The concentration of fermentable sugar was 103 g/l. The
circulation and simultaneous ventilation (arrow 8) were effected
by means of pump 20. After about 10 hours, fresh mash was
supplied continuously by means of a dosing pump, the mash having
the above mentioned sugar concentration, through,pipe 9. The
overflow rom fermentation stage 1 opened into the settling plant
consisting of degasifier 12 and settler 5. The s~ttled yeast from
the latter was returned by means of pump 13 into the fermentation
stage 1. When the fllling level was reached in settler 5, the
dosing of fresh mash was so adjusted that the discharge through 16




: . .. .
. . .

~ --~\

~ 2;~i2~

of settler 5 was completely fermented. In this manner the yeast
was constantly enriched in the entire system, and the supply of
fresh mash could be constantly increased according to the pre-
vailing yeast concentration until excess yeast was found in the
discharge from 16 of the settler. The amount of fresh mash was
so adjusted that the yeast just completely fermented the charged
sugar. This dosing rate was reduced by not more than one third
of the value required for complete ferrllentation, i.e. the minimum
rate of feed in this case was 0.5 1 mash per liter of fermentation
vat contents per hour. At this rate of feed the retention periods
in the fermentation stage were 1.33 and 2 hours. The yeast con-
centration in the fermentation stage attained a maximum of 15~/o
of the concentration required for complete fermentation~ The optimum
yeast concentration in the fermentation stage was 41 to 62 g dry
~ yeast per liter with a retention period of 2 hours in the fermenta-
i tion stage. The removal of the excess yeast was effected either
jointly with the overflow, or in concentrated form by means of
the pump from the bottom part of the settler 5.
The fermentation was carried out over a longer period of
time equilibrium state. Alcohol concentrations between 6.44 - 6.73%
by volume were measured in discharge 16. Thus, the yield was be-
tween 625 and 653 lit~ers alc~ol per 100 kg fermentabLe sugar,
which in this case was almost excIusively saccharose. The rate of
feed of mash was 0.73 to 0.79 leters per liter fermentation stage
contents per hour. Thus, the productivity is 47.5 - 50.9 ml alcohol
`~ per liter fermentation stage contents per hour. The production o~

.~ `
$, -10-



excess yeast was between 1.36 and 5 g dry yeast substance per
liter of discharged mash. A compilation of the test values
is found in the table below.
In another test series a two-sta~e pilot plant similar
to th~t of FIG. 4 was used. The rate of feed of fresh mash was
set at 6.75 liters of mash and the yeast concentration in the
fermentation stage was about 55 g per liter. The overflow of
settler 5 with the excess yeast produced was introduced into a
second fermentation stage having a capacity of 48 liters, to
which a settler was likewise connected to return the yeast into
the second fermentation stage. To the discharge from the first
settling stage 2 were continuously added 1.62 liters concentrated
mash per hour in the form of a molasses solution containing
about 400 g sugar per liter. The alcohol concentration in
outlet 11' of the second settling stage was 10.5D/D by volume.
The productivity of the two fermentation stages together was
thus about 15.3 ml alcohol per liter fermentation stage content
per hour.
The following table aets forth the productivity and yield
of ethyl alcohol and yeast in the continuous intensive process
according to FIG. 6.

\

~252~

Test period Sugar in Yield of Excess Yeast Productivity *)
24 hours each g/l mash Ethylalcohol T.S. -~) Ethylalcohol Yeast
in in ml/kg g/l mash ml/l h g/l h
vol% sugar


1 103 6.44 625 2.8 50.9 2.21
2 103 6.73 653 5.0 50.7 3.76
3 103 6.4~ 629 2.76 47.5 2.02
4 106 6.66 628 1.89 52.0 1.47.
110 6.80 618 1.85 5402 1.47
6 108 6.70 620 2.18 51.7 1.68
7 107 6.73 629 1.36 50.4 1.02
Average: 628.8 2.54 51.0 1.94
*) relates to ml and g respectively per liter fermentation stage
contents per hour
~) dry substance
While the invention has been illustrated in particular with
respect to specific apparatus and process conditions, it is
apparent that variations and modifications of the invention can
be made without departing from the spirit or scope thereof.




-12- .

Representative Drawing

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Administrative Status

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Administrative Status

Title Date
Forecasted Issue Date 1982-06-08
(22) Filed 1979-05-16
(45) Issued 1982-06-08
Expired 1999-06-08

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $0.00 1979-05-16
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
WAAGNER-BIRO AKTIENGESELLSCHAFT
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Drawings 1994-02-17 2 68
Claims 1994-02-17 4 114
Abstract 1994-02-17 1 33
Cover Page 1994-02-17 1 19
Description 1994-02-17 12 459