CN112391415B - Process for producing ethanol - Google Patents
Process for producing ethanol Download PDFInfo
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- CN112391415B CN112391415B CN202011205003.0A CN202011205003A CN112391415B CN 112391415 B CN112391415 B CN 112391415B CN 202011205003 A CN202011205003 A CN 202011205003A CN 112391415 B CN112391415 B CN 112391415B
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- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
- C12P7/00—Preparation of oxygen-containing organic compounds
- C12P7/02—Preparation of oxygen-containing organic compounds containing a hydroxy group
- C12P7/04—Preparation of oxygen-containing organic compounds containing a hydroxy group acyclic
- C12P7/06—Ethanol, i.e. non-beverage
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/10—Biofuels, e.g. bio-diesel
Abstract
The invention relates to the technical field of biology, and discloses a method for preparing ethanol, which comprises the following steps: (1) carrying out first propagation on the yeast strain to obtain first propagation yeast mash; (2) subjecting at least 85% by volume of said first expanded culture yeast mash to a first fermentation in a fermentation medium to obtain ethanol; (3) and performing second propagation on the rest first propagation yeast mash to obtain second propagation yeast mash, and performing second fermentation on at least part of the second propagation yeast mash in a fermentation culture medium to obtain ethanol. The method can obviously reduce the yeast consumption, the material consumption and the energy consumption, reduce the sewage quantity and reduce the production cost.
Description
Technical Field
The invention relates to the field of ethanol production, and in particular relates to a method for preparing ethanol.
Background
As the sewage treatment capacity of alcohol production enterprises has gradually become a bottleneck limiting the development of the enterprises, the sewage treatment burden of the enterprises can be reduced through thick mash fermentation, the pollution chance in the production link is reduced, and the DDGS production yield is improved, so that the method becomes the main process and development trend for producing fuel ethanol.
The alcohol content of the fuel ethanol can reach more than 15% through thick mash fermentation, but the consumption of auxiliary materials is increased along with the increase of the alcohol content of the fuel ethanol. Especially, the amount of yeast is generally 0.4-0.8 kg/ton wine, which increases the cost. Furthermore, mature yeast mash is supplied to the fermentation tanks at once, one yeast tank for each fermentation tank. And the CIP system is used for cleaning the wine mother tank, so that the consumption of electricity and alkali liquor is increased, the generated tank cleaning waste liquid also increases the burden of sewage treatment, and the energy conservation, emission reduction and clean production control of fuel ethanol are not facilitated.
Disclosure of Invention
The invention aims to solve the problems of high consumption of auxiliary materials (especially yeast) and high energy consumption in the production of fuel ethanol by thick mash fermentation, and provides a method for preparing ethanol, which can obviously reduce the consumption of the yeast, save materials and energy and further reduce the cost.
In order to achieve the above object, the present invention provides a method for producing ethanol, comprising:
(1) carrying out first propagation on the yeast strain to obtain first propagation yeast mash;
(2) subjecting at least 85% by volume of said first expanded culture yeast mash to a first fermentation in a fermentation medium to obtain ethanol;
(3) and performing second propagation on the rest first propagation yeast mash to obtain second propagation yeast mash, and performing second fermentation on at least part of the second propagation yeast mash in a fermentation culture medium to obtain ethanol.
When the method is adopted for preparing the ethanol, the yeast dosage can be obviously reduced, so that the yeast dosage is reduced by more than 50 percent.
The method of the invention can shorten the yeast propagation time, thereby shortening the time of the whole process and improving the production efficiency.
The method of the invention can also reduce material consumption and energy consumption, reduce sewage quantity and reduce production cost.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a method for preparing ethanol, which comprises the following steps:
(1) carrying out first propagation on yeast strains to obtain first propagation yeast mash;
(2) subjecting at least 85% by volume of said first expanded culture yeast mash to a first fermentation in a fermentation medium to obtain ethanol;
(3) and performing second propagation on the rest first propagation yeast mash to obtain second propagation yeast mash, and performing second fermentation on at least part of the second propagation yeast mash in a fermentation culture medium to obtain ethanol.
The method is more suitable for thick mash fermentation, namely the method is more suitable for fermentation process of fermenting the ethanol concentration in mature mash to be more than 12g/100mL (preferably 12.8-13.8g/100 mL).
In the present invention, the yeast strain may be a strain conventionally used in the art for fermentation to produce ethanol, such as Angel thick mash Saccharomyces cerevisiae high activity dry yeast produced by Angel Yeast GmbH in Hubei.
In the present invention, the yeast strain may be activated before the first expansion culture, wherein the activation may be performed in a shake flask or an activation tank.
The activation method may be a method conventionally used in the art, such as inoculating yeast strain into an activation tank, mixing with water, and activating to obtain activated yeast mash. Optionally, a carbon source, such as liquefied mash, may be added to the activation tank to activate the yeast species.
Wherein the preparation process of the liquefied mash may comprise: and (3) crushing, mixing and liquefying the starchy raw material to obtain liquefied mash. The liquefied mash may be prepared as desired by one skilled in the art according to conventional methods, and will not be described herein.
Wherein the type of the starchy material is not particularly limited,
in a preferred embodiment of the invention, the yeast species is activated prior to the first propagation to obtain an activated yeast mash. Preferably, the viable count in the activated yeast mash is more than or equal to 2.0 hundred million/mL. Under the preferable conditions, the activity of yeast can be improved, the lag phase can be shortened, and the culture time of the yeast can be shortened.
Wherein the activation medium for yeast activation is preferably a dilution of the liquefied mash having a dry matter content of 4-8 wt%. It will be appreciated that the activated medium may be obtained from a dilution of liquefied mash prepared by liquefaction.
Wherein the activating conditions may be conditions conventional in the art, preferably the activating conditions include: the temperature is 30-32 deg.C, pH is 4-7, and the time is 0.5-2 h.
In the present invention, the first expanding culture method may be an expanding culture method conventional in the art, and preferably, the first expanding culture method comprises: transferring the activated yeast mash to a yeast tank, and carrying out first propagation in the presence of a propagation medium; wherein, the first propagation method further comprises: and injecting the propagation culture medium into the yeast tank in the first propagation process, wherein the injection amount enables the liquid filling amount in the yeast tank to reach 75-85 vol%.
In the present invention, the volume ratio of the activated yeast mash to the wine mother tank can be selected within a wide range, and preferably, the activated yeast mash is 3 to 5% by volume with respect to 100 parts by volume of the wine mother tank. That is, the activated yeast mash provides a liquid loading of 3-5 vol%.
Although the object of the present invention can be achieved by directly injecting the propagation medium into the alcohol tank at a time in a predetermined amount for the first propagation, the growth rate of yeast can be increased and the propagation time can be shortened by injecting the propagation medium into the alcohol tank for the first propagation in a fed-batch manner for a long period of time.
Preferably, in the first expanding culture process, the injection manner of the expanding culture medium comprises: the injection amount of 0-2h ensures that the liquid filling amount of the wine mother tank reaches 15-20 vol%;
the injection amount of 2-4h ensures that the liquid filling amount of the wine mother tank reaches 32-40 volume percent;
the injection amount of the rest time is such that the liquid filling amount of the wine mother tank reaches 75-85 vol%.
In a preferred embodiment of the present invention, in the first expanding culture process, the injection manner of the expanding culture medium comprises: the injection amount of 0-2h ensures that the liquid filling amount of the wine mother tank reaches 15-20 vol%; the injection amount of 2-4h ensures that the liquid filling amount of the wine mother tank reaches 32-40 volume percent; the liquid content of the wine mother tank reaches 75-85 vol% in the first 60-80% of the rest time.
It is understood that 0-2h refers to the first two hours and 2-4h refers to the next two hours.
In a preferred embodiment of the present invention, the time of the first propagation is 8 hours or more, more preferably 8 to 12 hours. In the first expanding culture process, the injection mode of the expanding culture medium comprises the following steps: the injection amount of 0-2h ensures that the liquid filling amount of the wine mother tank reaches 15-20 vol%; the injection amount of 2-4h ensures that the liquid filling amount of the wine mother tank reaches 32-40 volume percent; the injection amount of 4-8h makes the liquid filling amount of the wine mother tank reach 75-85 vol%.
It should be understood that the injection may be performed continuously or intermittently, at a constant or variable rate, and that the injection rate may be controlled by one skilled in the art as appropriate. Preferably, the injection is performed in a continuous uniform manner. In the preferred case, the propagation of the yeast can be matched to the release rate of the sugar, avoiding inhibition of the sugar.
In a preferred embodiment of the invention, firstly, the propagation medium is injected into the wine mother tank at one time, and the volume of the injected propagation medium accounts for 2-5% of the volume of the wine mother tank; the activated yeast mash is then transferred to a wine mother tank.
Preferably, the first propagation condition is that the number of viable bacteria in the primary distiller's yeast obtained by the first propagation is more than or equal to 2.0 hundred million/mL.
Preferably, the conditions of the first propagation are such that the germination rate in the mash of the yeast obtained by the first propagation is 19% or more, more preferably 19-25%.
Preferably, the conditions of the first spread culture are such that the mortality rate in the mash of the yeast obtained by the first spread culture is 7% or less.
Preferably, the conditions of the first propagation include: the temperature is 30-31 deg.C, pH is 3.8-4.5, and the time is 8-12 h.
In the present invention, at least 85 vol% (e.g., can be 85 vol%, 88 vol%, 90 vol%, 92 vol%, 94 vol%, 96 vol%, 98 vol%, and any range therebetween) of the first expanded starter mash is first fermented in a fermentation medium to obtain ethanol. Preferably, at least 90% by volume of the first expanded culture yeast mash is subjected to a first fermentation in a fermentation medium to obtain ethanol. Under the preferable condition, the strain can be reserved for the second propagation on the premise of providing the fermented yeast mash to ensure the first fermentation, and the smooth culture effect of the second propagation is ensured.
And performing second propagation on the rest first propagation yeast mash, namely using the rest volume of the first propagation yeast mash as a strain of the second propagation for the second propagation.
In the present invention, preferably, the second propagation method comprises: in the second propagation process, a propagation medium is injected into the yeast tank, and the injection amount enables the liquid filling amount in the yeast tank to reach 75-85 vol%.
In a preferred embodiment of the present invention, the time of the second propagation is preferably 6-8 h. In the second expanding culture process, the injection mode of the expanding culture medium comprises the following steps: the injection amount of 0-3h ensures that the liquid filling amount of the wine mother tank reaches 32-40 volume percent; the injection amount of the residual time enables the liquid filling amount of the wine mother tank to reach 75-85 volume percent.
In a preferred embodiment of the invention, the time of the second propagation is 6-8 h. In the second expanding culture process, the injection mode of the expanding culture medium comprises the following steps: the injection amount of 0-3h ensures that the liquid filling amount of the wine mother tank reaches 32-40 volume percent; the liquid content of the wine mother tank reaches 75-85 vol% in the first 80-90% of the rest time.
Preferably, the conditions of the second propagation are such that the number of viable bacteria in the yeast mash obtained by the second propagation is more than or equal to 3.5 hundred million/mL.
Preferably, the conditions of the second propagation make the germination rate in the yeast mash obtained by the second propagation be more than 18%, and more preferably 18-25%.
Preferably, the conditions of the second propagation are such that the mortality rate in the mash of the yeast obtained by the second propagation is less than 9%.
Preferably, the second propagation conditions include: the temperature is 30-31 ℃, the pH is 3.8-4.5, and the time is 6-8 h.
In the present invention, the medium used in the expanding culture process may be a medium conventionally used in the art, and may be, for example, at least one of a nitrogen source, inorganic salts, trace elements, vitamins and liquefied mash required for yeast, preferably liquefied mash having a solid content of 30-35% and a pH of 3.8-4.5. The pH can be adjusted using common acids, such as sulfuric acid.
It is to be understood that the secondary spread culture of the yeast mash may also be processed in the manner of the primary spread culture of the yeast mash, followed by subsequent fermentation and tertiary spread culture, and as the case may be, spread culture multiple times in the manner described. Preferably, the whole of the mash obtained by the second propagation is transferred to a fermentation tank for fermentation.
In the present invention, the conditions of the first fermentation and the second fermentation may be the same or different, and those skilled in the art can adjust the conditions according to actual conditions. Preferably, the conditions of the first fermentation and the second fermentation each independently comprise: the fermentation temperature is 32-33 deg.C, and pH is 3.8-4.5.
The fermentation time may be from the start of inoculation to the appearance of the decline phase of yeast growth (i.e. fermentation time is lag phase, log phase plus stationary phase), preferably fermentation time is 60-70 h.
In the present invention, the medium used in the fermentation process may be a medium conventionally used in the art, and may be, for example, at least one of a nitrogen source, inorganic salts, trace elements, vitamins and liquefied mash required for yeast, preferably liquefied mash having a solid content of 30-35% and a pH of 3.8-4.5. The pH can be adjusted using common acids, such as sulfuric acid.
It will be appreciated that the first fermentation and the second fermentation are performed in different fermenters in order to increase the efficiency of production.
In the present invention, the volume ratio of the fermentation tank to the wine mother tank can be selected within a wide range, and preferably, the volume ratio of the fermentation tank to the wine mother tank is 3 to 5: 1.
the fermentation product ethanol can be separated and refined by conventional methods according to the requirements of different industrial products (such as fuel alcohol requiring ethanol with purity of more than 99%), such as distillation, concentration and water removal.
The present invention will be described in detail below by way of examples.
In the following examples, reagents and materials used are all commercially available unless otherwise specified.
In the following examples, the yeast is Angel thick mash Saccharomyces cerevisiae high activity dry yeast from Angel Yeast of Hubei.
In the following examples, the viable cell count, mortality, and budding rate of yeast were measured by microscopic counting.
In the following examples, an activation tank having a volume of 30m was used 3 The volume of the wine mother tank is 800m 3 The volume of the fermentation tank is 3300m 3 。
Preparation examples
This preparation example is illustrative of a method for preparing a liquefied mash
The corn grains are crushed, the crushing granularity reaches 20 meshes, the sieving rate of undersize products reaches more than 90 percent, the crushed mixed powder is mixed with process water and then stirred, amylase is added, the temperature and the retention time are controlled, the pH value is adjusted to be 4.2-4.4, and liquefied mash with the dry matter weight of about 32 percent is prepared.
Example 1
This example illustrates the process for producing ethanol according to the present invention
(1) And (3) activation: adding 20m into the activation tank 3 Water of (2) and 5m 3 The liquefied mash is mixed evenly, then 100kg of dry yeast is added into an activation tank, and the activated yeast mash is obtained after activation for 60min under the condition that the temperature is 31 ℃. The active bacteria number in the activated yeast mash is over 2.0 hundred million/mL.
(2) First expanding culture: adding 20m into yeast tank 3 Then the activated yeast mash obtained in the step (1) is fully injected into a wine mother tank, ventilation stirring is carried out, and the liquefied mash is fed. Wherein the feed rate of the liquefied mash is as follows: the rate of 0-2h is 51m 3 The rate of 2-4h is 70m 3 A rate of 4 to 8h of 91m 3 H is used as the reference value. Wherein, the first expanding culture condition comprises: the temperature is 30-31 ℃, the pH is controlled within the range of 3.9-4.1, and the time is 10 h.
After the first propagation, the viable count in the obtained first propagation yeast mash is about 2.2 hundred million/mL, the germination rate is 22.1%, and the death rate is 4.7%.
Conveying the first expanded culture yeast mash to a fermentation tank A for fermentation, wherein 80m remains in the yeast tank 3 The first expanding culture of the yeast mash is used for the second expanding culture.
(3) Second expanding culture: and (4) adding the liquefied mash into the yeast tank, ventilating and stirring, and performing secondary expanding culture. Wherein the feed rate of the liquefied mash is as follows: the velocity of 0-3h is 71m 3 The rate of 3-7h is 90m 3 H is used as the reference value. Wherein, the second condition of expanding culture comprises: the temperature is 30-31 ℃, the pH is controlled within the range of 3.9-4.1, and the time is 7.5 h.
After the second propagation, the number of viable bacteria in the obtained second propagation yeast mash is more than 3.5 hundred million/mL, the germination rate is 21.3 percent, and the death rate is 5.6 percent.
And conveying all the second propagation yeast mash into a fermentation tank B for fermentation, and cleaning the yeast tank by using a CIP system.
(4) Fermentation: and conveying the yeast mash subjected to the first propagation into a fermentation tank A, injecting the liquefied mash to a liquid level of 90%, stopping injecting the liquefied mash, and starting fermentation. And (4) conveying the yeast mash subjected to the second propagation into a fermentation tank B, injecting the liquefied mash to 90% of the liquid level, and starting fermentation. In the fermentation process, the temperature is 32.5-33 ℃ after 0-24h, the temperature is 32-32.5 ℃ after 24h, the pH is controlled within the range of 3.9-4.1, and the fermentation is finished after 68 h.
The mass content of ethanol in the mature mash of the fermentation tank A and the fermentation tank B is 12.98g/100mL and 13.02g/100mL respectively.
And (3) separating, rectifying and dehydrating mature mash obtained by fermentation to obtain fuel ethanol and a byproduct DDGS.
Example 2
This example illustrates the process for producing ethanol according to the present invention
(1) And (3) activation: the propagation was carried out as described in example 1.
(2) First expanding culture: adding 20m into yeast tank 3 Then the activated yeast mash obtained in the step (1) is completely poured into a wine mother tank, ventilated and stirred, and the liquefied mash is fed in a flowing mode. Wherein the feed rate of the liquefied mash is as follows: the velocity of 0-2h is 40m 3 The rate of 2-4h is 70m 3 The rate of 4-8h is 85m 3 H is used as the reference value. Wherein, the first expanding culture condition comprises: the temperature is 30-31 ℃, the pH is controlled within the range of 3.9-4.1, and the time is 10 h.
After the first propagation, the number of viable bacteria in the obtained first propagation yeast mash is more than 2.0 hundred million/mL, the germination rate is 20.7 percent, and the death rate is 5.8 percent.
Conveying the first expanded culture yeast mash into a fermentation tank A for fermentation, wherein 60m of yeast mash remains in the yeast tank 3 The first expanding culture of the yeast mash is used for the second expanding culture.
(3) Second expanding culture: the liquefied mash was fed into the yeast tank, stirred under aeration, and subjected to a second propagation under the conditions described in example 1. Wherein the feed rate of the liquefied mash is as follows: the velocity of 0-3h is 66m 3 The rate of 3-7h is 86m 3 /h。
After the second propagation, the number of viable bacteria in the obtained second propagation yeast mash is more than 3.5 hundred million/mL, the germination rate is 19.1 percent, and the death rate is 7.7 percent.
And conveying all the second expanded culture yeast mash into a fermentation tank B for fermentation, and cleaning a yeast tank CIP.
(4) And (3) fermentation: the fermentation was carried out as described in example 1. The mass contents of ethanol in mature mash of the fermentation tank A and the fermentation tank B are respectively 12.86g/100mL and 12.75g/100 mL.
And (3) separating, rectifying and dehydrating mature mash obtained by fermentation to obtain fuel ethanol and a byproduct DDGS.
Example 3
This example illustrates the process for the production of ethanol according to the invention
(1) And (3) activation: the propagation was carried out as described in example 1.
(2) First expanding culture: adding 20m into yeast tank 3 Then the activated yeast mash obtained in the step (1) is completely poured into a wine mother tank, ventilated and stirred, and the liquefied mash is fed in a flowing mode. Wherein the feed rate of the liquefied mash is as follows: the velocity of 0-2h is 57m 3 A rate of 2 to 4h of 80m 3 A rate of 4-8h of 90m 3 H is the ratio of the total weight of the catalyst to the total weight of the catalyst. Wherein, the first expanding culture condition comprises: the temperature is 30-31 ℃, the pH is controlled within the range of 3.9-4.1, and the time is 10 h.
After the first propagation, the number of viable bacteria in the obtained first propagation yeast mash is more than 2.0 hundred million/mL, the germination rate is 19.9 percent, and the death rate is 6.3 percent.
Delivering the first expanded culture yeast mash into a fermentation tank A for fermentation, wherein 70m of the yeast mash remains in the yeast tank 3 The first expanding culture of the yeast mash is used for the second expanding culture.
(3) Second expanding culture: the liquefied mash was fed into the yeast tank, stirred under aeration, and subjected to a second propagation under the conditions described in example 1. Wherein the feed rate of the liquefied mash is as follows: the velocity of 0-3h is 83m 3 A rate of from 3 to 7h of 90m 3 /h。
After the second propagation, the number of viable bacteria in the obtained second propagation yeast mash is more than 3.5 hundred million/mL, the germination rate is 20 percent, and the death rate is 8.9 percent.
And conveying all the second propagation yeast mash into a fermentation tank B for fermentation, and cleaning a yeast tank CIP.
(4) Fermentation: the fermentation was carried out as described in example 1. The mass contents of ethanol in mature mash of the fermentation tank A and the fermentation tank B are respectively 12.85g/100mL and 12.65g/100 mL.
And (3) separating, rectifying and dehydrating mature mash obtained by fermentation to obtain fuel ethanol and a byproduct DDGS.
Example 4
This example illustrates the process for the production of ethanol according to the invention
(1) Activation: the propagation was carried out as described in example 1.
(2) First expanding culture: the first propagation was carried out as described in example 1, except that the feeding rate was 61m for 4-10h 3 H is used as the reference value. After the first propagation, the viable count in the obtained first propagation yeast mash is more than 2.0 hundred million/mL, the germination rate is 19.4%, and the death rate is 7.6%.
(3) Second expanding culture: performing a second propagation according to the method described in example 1, wherein the viable count of the obtained second propagation fermented mash is 3.5 hundred million/mL or more, the germination rate is 17.9%, and the mortality rate is 10.3%.
(4) And (3) fermentation: fermentation was carried out as described in example 1, with the ethanol content in the mature mash of fermentors A and B being 12.81g/100mL and 12.62g/100mL, respectively.
Example 5
This example illustrates the process for producing ethanol according to the present invention
(1) And (3) activation: the propagation was carried out as described in example 1.
(2) First expanding culture: the first spread culture was carried out in the same manner as described in example 1, except that the liquefied mash was fed at a uniform rate over a total of 8 hours from 0 to 8 hours and the volume of the fed liquefied mash was 606m 3 . After the first propagation, the number of viable bacteria in the obtained first propagation yeast mash is more than 2.0 hundred million/mL, the germination rate is 18.2 percent, and the death rate is 7.5 percent.
(3) Second expanding culture: performing a second propagation according to the method described in example 1, wherein the viable count of the obtained second propagation fermented mash is 3.5 hundred million/mL or more, the germination rate is 17.5%, and the mortality rate is 10.8%.
(4) Fermentation: fermentation was carried out as described in example 1, with the ethanol content in the mature mash of fermentors A and B being 12.78g/100mL and 12.67g/100mL, respectively.
Example 6
This example illustrates the process for producing ethanol according to the present invention
(1) And (3) activation: the propagation was carried out as described in example 1.
(2) First expanding culture: the first expansion culture was carried out as described in example 1, except that starting from 0h, 90m 3 The velocity of/h is fed until 606m 3 The whole volume of the liquefied mash is fed to the fermenter. After the first propagation, the number of viable bacteria in the obtained first propagation yeast mash is more than 1.5 hundred million/mL, the germination rate is 17.6%, and the death rate is 8%.
(3) Second expanding culture: and (3) carrying out second propagation according to the method described in example 1, wherein after the second propagation, the number of viable bacteria in the obtained second propagation fermented mash is more than 3.5 hundred million/mL, the germination rate is 16.8%, and the death rate is 11.4%.
(4) And (3) fermentation: fermentation was carried out as described in example 1, with the ethanol content in the mature mash of fermentors A and B being 12.63g/100mL and 12.54g/100mL, respectively.
Example 7
This example illustrates the process for the production of ethanol according to the invention
(1) Activation: the propagation was carried out as described in example 1.
(2) First expanding culture: the first expansion culture was performed as described in example 1.
(3) Second expanding culture: a second propagation was carried out as described in example 1, except that the fedbatch rate was 80m for 3-7.5h 3 H is used as the reference value. After the second propagation, the number of viable bacteria in the obtained second propagation yeast mash is more than 3.5 hundred million/mL, the germination rate is 18.4 percent, and the death rate is 7.6 percent.
(4) Fermentation: fermentation was carried out as described in example 1, with the ethanol content in the mature mash of fermentor A and fermentor B being 12.99g/100mL and 12.69g/100mL, respectively.
Example 8
This example illustrates the process for producing ethanol according to the present invention
(1) And (3) activation: the propagation was carried out as described in example 1.
(2) First expanding culture: the first expansion culture was carried out as described in example 1.
(3) Second expanding culture: a second propagation was carried out in accordance with the method described in example 1, except that the mash was fed at a uniform rate over a total of 7 hours over a period of 0-7h, the volume of the fed-in mash being 573m 3 . After the second propagation, the number of viable bacteria in the obtained second propagation yeast mash is more than 3.5 hundred million/mL, the germination rate is 17.8%, and the death rate is 8.2%.
(4) And (3) fermentation: fermentation was carried out as described in example 1, with the ethanol contents in the mature mash of fermentors A and B being 12.97g/100mL and 12.61g/100mL, respectively.
Example 9
This example illustrates the process for producing ethanol according to the present invention
(1) And (3) activation: the propagation was carried out as described in example 1.
(2) First expanding culture: the first expansion culture was carried out as described in example 1.
(3) Second expanding culture: a second expansion culture was carried out as described in example 1, except that starting from 0h, 90m 3 The rate of/h is fed until 573m 3 The whole volume of the liquefied mash is fed to the fermenter. After the second propagation, the number of viable bacteria in the obtained second propagation yeast mash is more than 3.0 hundred million/mL, the germination rate is 16.5%, and the death rate is 10.5%.
(4) Fermentation: fermentation was carried out as described in example 1, with the ethanol content in the mature mash of fermentor A and fermentor B being 12.98g/100mL and 12.35g/100mL, respectively.
Comparative example 1
This comparative example serves to illustrate a reference process for the preparation of ethanol
(1) Activation: activation was carried out as described in example 1.
(2) Expanding culture: adding 20m into yeast tank 3 Then the activated yeast mash obtained in step (1) is all poured into a wine mother tank, stirred under ventilation and kept at 75m 3 The liquid mash is fed in at a rate of/h. Wherein, the condition of expanding culture comprises: the temperature is 30-31 ℃, the pH is controlled within the range of 3.9-4.1, and the time is 10 h.
After the propagation is finished, the number of viable bacteria in the obtained propagation fermented glutinous rice is more than 2.0 hundred million/mL, the germination rate is 19.7 percent, and the death rate is 5.4 percent.
And (4) conveying all the yeast mash obtained by expanding culture to a fermentation tank for fermentation.
(3) Fermentation: the fermentation was carried out as described in example 1, with a mass content of ethanol in the mature mash of the fermenter of 12.85g/100 mL. After the fermentation is finished, the CPI system is used for cleaning equipment, and the fermentation is carried out again according to the same method, wherein the mass content of the ethanol in the mature mash of the fermentation tank is 12.87g/100 mL.
From the above results, it can be seen that the method of the present invention can shorten the production period and improve the fermentation efficiency and yield with a reduced yeast usage amount of about 50%. In a preferable case, the activity and fermentation yield of yeast can be further improved by controlling the injection rate of the first spread-cultured mash, the remaining amount of the first spread-cultured yeast mash, and the injection rate of the second spread-cultured mash.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (9)
1. A method for preparing ethanol by thick mash fermentation is characterized by comprising the following steps:
(1) carrying out first propagation on the yeast strain to obtain first propagation yeast mash;
(2) subjecting at least 85% by volume of said first expanded culture yeast mash to a first fermentation in a fermentation medium to obtain ethanol;
(3) performing second propagation on the rest first propagation yeast mash to obtain second propagation yeast mash, and performing second fermentation on at least part of the second propagation yeast mash in a fermentation culture medium to obtain ethanol;
wherein, the method is suitable for the fermentation process of the ethanol concentration in the fermented mature mash being more than 12g/100 mL;
the first propagation method comprises the following steps: transferring the activated yeast mash to a yeast tank, and carrying out first propagation in the presence of a propagation medium; 3-5% of activated yeast mash by volume relative to 100 parts by volume of the yeast tank;
wherein, the first propagation method further comprises: injecting the propagation culture medium into the yeast tank in the first propagation process, wherein the injection amount enables the liquid filling amount in the yeast tank to reach 75-85% by volume;
in the first expanding culture process, the injection mode of the expanding culture medium comprises the following steps: the injection amount of 0-2h ensures that the liquid filling amount of the wine mother tank reaches 15-20 vol%;
the injection amount of 2-4h ensures that the liquid filling amount of the wine mother tank reaches 32-40% by volume;
the injection amount of the residual time enables the liquid filling amount of the wine mother tank to reach 75-85 volume percent;
the second propagation method comprises the following steps: in the second propagation process, a propagation medium is injected into the yeast tank, and the injection amount enables the liquid filling amount in the yeast tank to reach 75-85% by volume;
in the second expanding culture process, the injection mode of the expanding culture medium comprises the following steps: the injection amount of 0-3h ensures that the liquid filling amount of the wine mother tank reaches 32-40 volume percent;
the injection amount of the residual time enables the liquid filling amount of the wine mother tank to reach 75-85 volume percent;
wherein the time of the first propagation is 8-12h, and the time of the second propagation is 6-8 h.
2. The method of claim 1, wherein the yeast species is activated prior to the first propagation to obtain an activated yeast mash.
3. The method of claim 2, wherein the number of viable bacteria in the activated yeast mash is greater than or equal to 2.0 billion/mL.
4. The method of claim 2, wherein the activating conditions comprise: the temperature is 30-32 deg.C, pH is 4-7, and the time is 0.5-2 h.
5. The method according to any one of claims 1 to 4, wherein the conditions of the first propagation are such that the number of viable bacteria in the beer obtained by the first propagation is not less than 2.0 hundred million/mL.
6. The method of claim 5, wherein the conditions of the first spread culture comprise: the temperature is 30-31 deg.C, and pH is 3.8-4.5.
7. The method of claim 1, wherein the second propagation conditions are such that the viable count of the mash obtained by the second propagation is greater than or equal to 3.5 hundred million/mL.
8. The method of claim 7, wherein the conditions of the second propagation comprise: the temperature is 30-31 deg.C, and pH is 3.8-4.5.
9. The method of claim 1, wherein the conditions of the first fermentation and the second fermentation each independently comprise: the temperature is 32-33 deg.C, and pH is 3.8-4.5.
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