Yeast preparation method

Abstract

The present invention relates to the technical field of fermentation, and in particular to a method for preparing yeast. The preparation method comprises the following steps: providing yeast fermentation wastewater, evaporating and concentrating the yeast fermentation wastewater, and collecting condensed water; fermenting seed yeast using fermentation bottom water and molasses treatment liquid to obtain yeast; wherein the fermentation bottom water includes the condensed water; and / or the treatment method of the molasses treatment liquid includes the step of diluting molasses with the condensed water. The process parameters of the fermentation treatment include: regulating the fermentation time and / or the amount of molasses treatment liquid added, so that the material index and material conversion rate of the obtained yeast meet the quality conditions at the same time. Under the premise of maintaining the quality of the yeast, the present invention has a simple treatment method for yeast fermentation wastewater, and a large amount of yeast fermentation wastewater can be reused, thereby achieving the application effect of energy saving and emission reduction.

Description

Technical Field

[0001] The invention relates to the technical field of fermentation, in particular to a method for preparing yeast. Background Art

[0002] During yeast production, fermentation water is usually added to the fermentation tank first, and then molasses and other raw materials are added for fermentation after seed yeast is inoculated. Molasses is generally selected as sugarcane molasses or beet molasses, which are often used in the fermentation process of extract yeast due to its rich ingredients. After fermentation, the fermentation clear liquid contains substances that are not used by yeast and metabolites produced by yeast metabolism, including rich nitrogen, phosphorus, potassium, calcium and macromolecular organic substances such as caramel, humic acid, and fulvic acid.

[0003] In the past, there are many methods for treating fermentation wastewater, such as evaporating and concentrating yeast fermentation wastewater with molasses as raw material, spray drying the concentrate to obtain organic fertilizer, and discharging the condensed water after treatment; for example, evaporating and concentrating yeast fermentation wastewater with molasses as raw material, filtering the condensed water through an osmotic membrane, and then reusing it in the fermentation process as dilution water.

[0004] In the previous treatment methods, if yeast fermentation wastewater is discharged directly or simply treated before discharge, it is difficult to treat it to the discharge standard because it is a high-concentration organic wastewater with poor biochemical treatment performance. After treatment such as osmotic membrane filtration, the process is relatively cumbersome and the reuse ratio of yeast fermentation wastewater is small. Summary of the invention

[0005] Based on this, the present invention provides a method for preparing yeast by utilizing yeast fermentation wastewater. Under the premise of maintaining the quality of the yeast, the treatment method of the yeast fermentation wastewater is simple and the reuse amount of the yeast fermentation wastewater is large.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing yeast comprises the following steps:

[0008] Providing yeast fermentation wastewater, performing evaporation and concentration treatment on the yeast fermentation wastewater, and collecting condensed water;

[0009] The yeast seed is fermented by using fermentation bottom water and molasses treatment liquid to obtain yeast; wherein the fermentation bottom water includes the condensed water; and / or the method for treating the molasses treatment liquid includes the step of diluting molasses by using the condensed water;

[0010] The process parameters of the fermentation treatment include: adjusting the fermentation time and / or the amount of molasses treatment solution added, so that the material index and material conversion rate of the obtained yeast meet the following conditions at the same time:

[0011] The proportion of protein in the dry weight of the yeast is not less than 60wt%; the proportion of nucleic acid in the dry weight of the yeast is not less than 8wt%; the viable cell rate is ≥98%; and the sugar conversion rate is ≥78%.

[0012] In some embodiments, the fermentation time is 12 hours to 16 hours.

[0013] In some embodiments, the condensed water is used to dilute the molasses to a total sugar concentration of 30 wt%±0.1 wt% in the dilution, and 3800 mL to 4100 mL of the molasses treatment solution is added for every 220 g to 230 g of seed yeast.

[0014] In some embodiments, the molasses treatment liquid is introduced by a feeding method, and the process parameters of the feeding include: a maximum flow rate of 350 ml / h to 450 ml / h.

[0015] In some embodiments, the molasses treatment solution is introduced by a feeding method, and the process parameters of the feeding include: the time to reach the maximum flow rate is 7h to 9h.

[0016] In some embodiments, the mass percentage of the condensed water in the fermentation bottom water is 25wt% to 100wt%.

[0017] In some embodiments, 4.1 L to 4.3 L of the fermentation bottom water is added for every 220 g to 230 g of seed yeast.

[0018] In some of the embodiments, the process parameters of the fermentation treatment also include: controlling the ventilation volume of the fermentation system so that the maximum ventilation volume is 25L / min-30L / min, and the time to reach the maximum ventilation volume is 5h to 7h.

[0019] In some embodiments, the process parameters of the fermentation treatment also include: controlling the pH value of the fermentation system to be 4.0-6.5.

[0020] In some embodiments, the process parameters of the fermentation treatment also include: the fermentation temperature is 28°C to 34°C.

[0021] In some embodiments, the step of obtaining yeast fermentation wastewater includes:

[0022] The fermentation liquid obtained after the fermentation treatment is subjected to solid-liquid separation treatment and washing treatment to obtain yeast fermentation wastewater.

[0023] In some embodiments, the evaporation concentration process is performed to obtain a solid content of 50 wt % to 60 wt %.

[0024] In some embodiments, the seed yeast is Saccharomyces cerevisiae.

[0025] Compared with the traditional solution, the present invention has the following beneficial effects:

[0026] The present invention uses yeast fermentation wastewater to prepare yeast. Different from the previous method, the condensed water of yeast fermentation wastewater is not treated or discharged after simple treatment or returned to the fermentation treatment process as dilution water after treatment such as filtration by osmotic membrane, the present invention can directly use condensed water as dilution water for molasses, and in order to increase the reuse amount of yeast fermentation wastewater, the present invention can directly use condensed water as fermentation bottom water. Because the inventor of the present invention found that at this time, the ideal quality of yeast can be obtained by adjusting the fermentation time and / or the addition amount of molasses treatment liquid of the fermentation treatment process, that is, the adverse effect of directly using condensed water as fermentation bottom water and / or molasses dilution water back to the fermentation treatment process (especially directly using condensed water as fermentation bottom water) on the quality of yeast fermentation can be compensated by adjusting the fermentation time of the fermentation treatment process and the addition amount of molasses treatment liquid. Prepare yeast by the method of the present invention, not only the treatment method of yeast fermentation wastewater is simple, and the reuse amount of yeast fermentation wastewater is large, but also the quality of yeast is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0028] Figure 1 The present invention is a process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below in conjunction with specific embodiments. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0031] the term

[0032] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0033] In the present invention, "plurality", "multiple", "multiple times", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0034] In the present invention, "combinations thereof", "any combinations thereof", "any combination thereof" and the like include all suitable combinations of any two or more of the listed items.

[0035] In the present invention, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc. shall be based on the ability to implement the technical solution of the present invention, solve the technical problem of the present invention, and achieve the expected technical effect of the present invention.

[0036] In the present invention, “preferred”, “better”, “more preferred” and “suitable” are only used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute limitations on the scope of protection of the present invention.

[0037] In the present invention, the words “further”, “furthermore”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present invention.

[0038] In the present invention, "optionally", "optional" and "optional" refer to optional, that is, to any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0039] In the present invention, in the "first aspect", "second aspect", "third aspect", "fourth aspect", etc., the terms "first", "second", "third", "fourth", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0040] In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0041] In the present invention, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1 to 10, indicating that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0042] The temperature parameters in the present invention, if not specifically limited, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0043] In the present invention, when it comes to percentage content, unless otherwise specified, for solid-liquid mixing and solid-solid mixing, it refers to mass percentage, and for liquid-liquid mixing, it refers to volume percentage.

[0044] In the present invention, when it comes to percentage concentration, unless otherwise specified, it refers to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of the component.

[0045] In the present invention, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass volume percentage.

[0046] See also Figure 1 In one embodiment, a method for preparing yeast comprises the following steps:

[0047] Yeast fermentation wastewater is provided, the yeast fermentation wastewater is evaporated and concentrated, and condensed water is collected.

[0048] Optionally, the step of obtaining yeast fermentation wastewater comprises:

[0049] The fermentation liquid obtained after the fermentation treatment is subjected to solid-liquid separation treatment and washing treatment to obtain yeast fermentation wastewater.

[0050] In this embodiment, the yeast fermentation wastewater uses the fermentation liquid obtained after the fermentation treatment as the starting material. At this time, the fermentation treatment can use water as the fermentation bottom water, or the above-mentioned condensed water as the fermentation bottom water, or water and the above-mentioned condensed water as the fermentation bottom water. Similarly, at this time, the fermentation treatment can add molasses treatment liquid diluted with water, or add molasses treatment liquid diluted with the above-mentioned condensed water, or add molasses treatment liquid diluted with water and the above-mentioned condensed water.

[0051] Optionally, the evaporation concentration process is performed to a solid content of 50 wt % to 60 wt %.

[0052] In this embodiment, the fermentation bottom water and molasses treatment liquid are used to ferment the seed yeast to obtain yeast.

[0053] Optionally, the molasses treatment liquid is introduced by a feeding method, and the process parameters of the feeding include: a maximum flow rate of 350 ml / h to 450 ml / h.

[0054] Optionally, the molasses treatment liquid is introduced by a flow addition method, and the process parameters of the flow addition include: the time to reach the maximum flow rate is 7h to 9h.

[0055] Optionally, the fermentation process further comprises the step of adding a nutrient before adding the molasses processed liquid.

[0056] Further optionally, the nutrient is selected from one or more of vitamin B1, biotin and inorganic salts.

[0057] Further optionally, the inorganic salt is selected from magnesium sulfate and / or zinc sulfate.

[0058] In this embodiment, the fermentation bottom water includes the above-mentioned condensed water, and the method for treating the molasses treated liquid includes the step of diluting the molasses using the above-mentioned condensed water.

[0059] In other embodiments, the fermentation bottom water includes the above-mentioned condensed water, and the molasses processing liquid includes a step of diluting the molasses with water.

[0060] In other embodiments, the fermentation bottom water is water, and the method for treating the molasses treated liquid includes the step of diluting the molasses using the condensed water.

[0061] In this embodiment, the mass proportion of the condensed water in the fermentation bottom water is 25wt% to 100wt%.

[0062] In this embodiment, the process parameters of the fermentation process include: adjusting the fermentation time and / or the amount of molasses treatment solution added, so that the material index and material conversion rate of the obtained yeast simultaneously meet the following conditions:

[0063] The proportion of protein in the dry weight of the yeast is not less than 60wt%; the proportion of nucleic acid in the dry weight of the yeast is not less than 8wt%; the viable cell rate is ≥98%; and the sugar conversion rate is ≥78%.

[0064] Optionally, the fermentation time is 12 h to 16 h.

[0065] Optionally, the condensed water is used to dilute the molasses to a total sugar concentration of 30 wt%±0.1 wt% in the dilution, and 3800 mL to 4100 mL of the molasses treatment solution is added for every 220 g to 230 g of seed yeast.

[0066] Optionally, 4.1 L to 4.3 L of the fermentation bottom water is added for every 220 g to 230 g of seed yeast.

[0067] In this embodiment, the seed yeast is Saccharomyces cerevisiae.

[0068] In some embodiments, the process parameters of the fermentation treatment also include: controlling the ventilation volume of the fermentation system so that the maximum ventilation volume is 25L / min-30L / min, and the time to reach the maximum ventilation volume is 5h to 7h.

[0069] In some embodiments, the process parameters of the fermentation treatment further include: controlling the pH value of the fermentation system to be 4.0-6.5.

[0070] In some embodiments, the process parameters of the fermentation treatment also include: the fermentation temperature is 28°C to 34°C.

[0071] In this embodiment, yeast is prepared using yeast fermentation wastewater. Different from the previous method, the condensed water of yeast fermentation wastewater is not treated or discharged after simple treatment or returned to the fermentation treatment process as dilution water after treatment such as filtration by osmotic membrane, in this embodiment, condensed water can be directly used as dilution water for molasses, and in order to increase the reuse amount of yeast fermentation wastewater, condensed water can be directly used as fermentation bottom water in this embodiment. Because the inventor found that at this time, the ideal quality of yeast can be obtained by adjusting the fermentation time and / or the addition amount of molasses treatment liquid of the fermentation treatment process, that is, the adverse effect of directly using condensed water as fermentation bottom water and / or dilution water for molasses back to the fermentation treatment process (especially directly using condensed water as fermentation bottom water) on the quality of yeast fermentation can be compensated by adjusting the fermentation time of the fermentation treatment process and the addition amount of molasses treatment liquid. Prepare yeast by the method of this embodiment, not only the treatment method of yeast fermentation wastewater is simple, but also the reuse amount of yeast fermentation wastewater is large, and the quality of yeast is also good.

[0072] The following is further described in conjunction with specific embodiments and comparative examples. The raw materials involved in the following specific embodiments, unless otherwise specified, can all be sourced from commercial sources. The instruments used, unless otherwise specified, can all be sourced from commercial sources. The processes involved, unless otherwise specified, are all routinely selected by those skilled in the art.

[0073] 1 Materials

[0074] 1.1 Bacterial strains Saccharomyces cerevisiae strain YC-1 (preserved in the laboratory).

[0075] 1.2 First molasses treatment liquid

[0076] Take sugarcane molasses (total sugar concentration is about 48wt%), add process soft water to dilute to a total sugar concentration of 30wt%, boil for 5 minutes, let stand and settle, centrifuge (6000rpm, 10min) to obtain a supernatant, and then sterilize at 115°C and 0.1Mpa for 15min to obtain a first molasses treatment liquid for standby use.

[0077] 1.3 Yeast fermentation wastewater

[0078] Take the fermentation liquid of the comparative example 1 under 2.3.1, and separate about 9L of the fermentation liquid by a common vertical centrifuge (4000rpm, 10min) to obtain a supernatant (referred to as the first wastewater) and yeast;

[0079] The obtained yeast is washed with process soft water and then centrifuged to obtain washing water (recorded as the second wastewater) and yeast;

[0080] Combine the first wastewater and the second wastewater to obtain yeast fermentation wastewater, about 10L, for standby use.

[0081] 1.4 Condensation

[0082] The yeast fermentation wastewater under Item 1.3 is evaporated and concentrated in batches using a rotary evaporator to a solid content of 50wt% to 60wt%. The solid detection method is carried out in accordance with "GB5009.3-2016 Direct Drying Method". The yeast fermentation wastewater is placed in the heating unit of the rotary evaporator. During the rotation of the container, the yeast fermentation wastewater exchanges heat with the heater and evaporates under the synergistic effect of the vacuum. The extracted steam is converted into condensed water after subsequent cooling. The indicators of the obtained condensed water are shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] 1.5 Second molasses treatment liquid

[0087] Take sugarcane molasses (total sugar concentration is about 48wt%), add the condensed water under item 1.4 to dilute to a total sugar concentration of 30wt%, boil for 5 minutes, let stand to settle, centrifuge (6000rpm, 10min) to obtain the supernatant, and then sterilize at 115℃, 0.1Mpa for 15min to obtain the second molasses treated liquid for standby use.

[0088] 2 Yeast fermentation process

[0089] 2.1 Shake flask expansion

[0090] Take a loop of the strain under 1.1 of the slant and inoculate it into a test tube containing 5mL of YPD medium, and activate and culture it at 30℃ and 150r / min for 24h. Transfer it to a shake flask medium containing 50mL of seed shake flask medium 1 according to the 2% inoculum, and culture it at 30℃ and 150r / min for 17h. Transfer all 50ml of seed culture solution 1 to a shake flask containing 450ml of seed shake flask medium 2, and culture it at 30℃ and 150r / min for 22h. Put the cultured seed solution 2 in a 4℃ refrigerator for later use.

[0091] 2.2 Seed fermentation

[0092] Add 4L of process soft water as fermentation bottom water into a 15L fermentation tank, add magnesium sulfate and zinc sulfate, adjust the pH to 4.0 with sulfuric acid, sterilize at 121°C and 0.1Mpa for 30min, add vitamin B1 and biotin after cooling to 30°C, inoculate the seed liquid 2 under item 2.1, feed the first molasses treatment liquid under item 1.2, terminate the fermentation after 26h, separate the fermentation liquid by centrifugation, resuspend the precipitate with process pure water to obtain seed yeast milk, the content of seed yeast in the seed yeast milk is about 650g / kg.

[0093] 2.3 Commercial fermentation

[0094] 2.3.1 Comparative Example 1 (fermentation bottom water is water, first molasses treatment liquid)

[0095] 4L of process soft water was added to the 15L fermenter as fermentation bottom water, magnesium sulfate and zinc sulfate were added, the pH was adjusted to 4.0 with sulfuric acid, and sterilized at 121°C and 0.1Mpa for 30min. Vitamin B1 and biotin were added after cooling to 30°C, and 300mL (about 350g) of the seed yeast milk cultured in Item 2.2 was inoculated, that is, about 225g of seed yeast was inoculated into the fermenter. At this time, the initial wet weight of the fermentation liquid (the wet weight of the seed yeast milk just inoculated into the fermenter) was about 50g / L, and then fermentation was carried out. The first molasses treated liquid under Item 1.2 was added to the fermenter by a feeding method, wherein the feeding amount of the first molasses treated liquid was about 4000mL, the time for the first molasses treated liquid to reach the maximum flow rate of 400ml / h was about 8h, and the maximum ventilation volume of 27L / min was reached after 6h. During the fermentation process, the pH value was controlled to gradually increase from 4 to 6.4, the fermentation temperature was controlled at 30°C, and the fermentation was terminated after 13h±0.4h.

[0096] Referring to the preparation method of yeast fermentation wastewater under 1.3, the obtained fermentation liquid is separated and washed to obtain yeast fermentation wastewater and yeast, and the yeast is subjected to quality inspection, wherein the determination of yeast viability rate is the percentage of the ratio of the number of live yeast cells to the total number of cells measured by a microscope and a blood cell counting plate after the yeast is resuspended with sterile physiological saline; the total colony count is detected according to the method of national standard GB4789.2-2016; the coliform group is detected according to the plate counting method in national standard GB4789.3-2016; the nucleic acid content is detected according to the perchloric acid method; the protein content is detected according to the Kjeldahl nitrogen determination method in national standard GB5009.5-2016; the sugar conversion rate is calculated according to the formula: sugar conversion rate = Y26 / M50×100%, wherein Y26 is the weight of the fermented yeast converted to 26% solids, and M50 is the weight of the total sugar consumed converted to 50wt%. The results are shown in Table 2.

[0097] Table 2

[0098]

[0099]

[0100] 2.3.2 Example 1 (fermentation bottom water is water, second molasses treatment liquid)

[0101] 4L of process soft water was added to the 15L fermenter as fermentation bottom water, magnesium sulfate and zinc sulfate were added, the pH was adjusted to 4.0 with sulfuric acid, and sterilized at 121°C and 0.1Mpa for 30min. Vitamin B1 and biotin were added after cooling to 30°C, and 300mL of the seed yeast milk cultured in 2.2 was inoculated, that is, about 225g of seed yeast was inoculated into the fermenter. At this time, the initial wet weight of the fermentation liquid was about 50g / L, and then fermentation was carried out. The second molasses treated liquid under 1.5 was added to the fermenter by feeding, wherein the feeding amount of the second molasses treated liquid was about 4000mL, the time for the second molasses treated liquid to reach the maximum flow rate was about 8h, and the maximum ventilation volume was reached after 6h. During the fermentation process, the pH value was controlled to gradually increase from 4 to 6.4, the fermentation temperature was controlled at 30°C, and the fermentation was terminated after 13h±0.4h.

[0102] Referring to the preparation method of yeast fermentation wastewater under 1.3, the obtained fermentation liquid is separated and washed to obtain yeast fermentation wastewater and yeast. The quality of the yeast is tested by referring to the detection method of Control Example 1 in 2.3.1. The results are shown in Table 3.

[0103] Table 3

[0104] Yeast index Test results Nucleic acid (dry basis) content (%) 8.77 Protein (dry basis) content (%) 66.05 Sugar conversion rate ≥80％ Viable cell rate (%) ≥98 Total colony count (cfu / g) <![CDATA[≤1×10 4 ]]> Coliform group (MPN / g) ≤2

[0105] 2.3.3 Example 2 (fermentation bottom water includes 25 wt% condensed water, second molasses treatment liquid)

[0106] 3L of process soft water and 1L of condensed water under 1.4 were added to a 15L fermenter as fermentation bottom water, magnesium sulfate and zinc sulfate were added, the pH was adjusted to 4.0 with sulfuric acid, and sterilized at 121°C and 0.1Mpa for 30min. Vitamin B1 and biotin were added after cooling to 30°C, and 300mL of seed yeast milk cultured in 2.2 was inoculated, that is, about 225g of seed yeast was inoculated into the fermenter. At this time, the initial wet weight of the fermentation liquid was about 50g / L, and then fermentation was carried out. The molasses treated liquid under 1.5 was added to the fermenter by feeding, wherein the feeding amount of the molasses treated liquid was about 4000mL, the time for the molasses treated liquid to reach the maximum flow rate was about 8h, and the maximum ventilation volume was reached after 6h. During the fermentation process, the pH value was controlled to gradually increase from 4 to 6.4, the fermentation temperature was controlled at 30°C, and the fermentation was terminated after 13h±0.4h.

[0107] Referring to the preparation method of yeast fermentation wastewater under 1.3, the obtained fermentation liquid is separated and washed to obtain yeast fermentation wastewater and yeast. The quality of the yeast is tested by referring to the detection method of Control Example 1 in 2.3.1. The results are shown in Table 4.

[0108] Table 4

[0109] Yeast index Test results Nucleic acid (dry basis) content (%) 8.51 Protein (dry basis) content (%) 64.11 Sugar conversion rate 78％～80％ Viable cell rate (%) ≥98 Total colony count (cfu / g) <![CDATA[≤1×10 4 ]]> Coliform group (MPN / g) ≤2

[0110] 2.3.4 Comparative Example 1 (fermentation bottom water includes 50 wt% condensed water, second molasses treatment liquid)

[0111] 2L of process soft water and 2L of condensed water under 1.4 were added to the 15L fermenter as fermentation bottom water, magnesium sulfate and zinc sulfate were added, the pH was adjusted to 4.0 with sulfuric acid, and sterilized at 121°C and 0.1Mpa for 30min. Vitamin B1 and biotin were added after cooling to 30°C, and 300mL of seed yeast milk cultured in 2.2 was inoculated, that is, about 225g of seed yeast was inoculated into the fermenter. At this time, the initial wet weight of the fermentation liquid was about 50g / L, and then fermentation was carried out. The second molasses treated liquid under 1.5 was added to the fermenter by feeding, wherein the feeding amount of the second molasses treated liquid was about 4000mL, the time for the second molasses treated liquid to reach the maximum flow rate was about 8h, and the maximum ventilation volume was reached after 6h. During the fermentation process, the pH value was controlled to gradually increase from 4 to 6.4, the fermentation temperature was controlled at 30°C, and the fermentation was terminated after 13h±0.4h.

[0112] Referring to the preparation method of yeast fermentation wastewater under 1.3, the obtained fermentation liquid was separated and washed to obtain yeast fermentation wastewater and yeast. The quality of the yeast was tested by referring to the detection method of Control Example 1 in 2.3.1. The results are shown in Table 5.

[0113] Table 5

[0114] Yeast index Test results Nucleic acid (dry basis) content (%) 8.33 Protein (dry basis) content (%) 63.48 Sugar conversion rate 75％～78％ Viable cell rate (%) ≥98 Total colony count (cfu / g) <![CDATA[≤1×10 4 <!-- 8 -->]]> Coliform group (MPN / g) ≤2

[0115] 2.3.5 Example 3 (fermentation bottom water includes 50 wt% condensed water, second molasses treatment liquid)

[0116] 2L of process soft water and 2L of condensed water under 1.4 were added to the 15L fermenter as fermentation bottom water, magnesium sulfate and zinc sulfate were added, the pH was adjusted to 4.0 with sulfuric acid, and sterilized at 121°C and 0.1Mpa for 30min. Vitamin B1 and biotin were added after cooling to 30°C, and 300mL of seed yeast milk cultured in 2.2 was inoculated, that is, about 225g of seed yeast was inoculated into the fermenter. At this time, the initial wet weight of the fermentation liquid was about 50g / L, and then fermentation was carried out. The second molasses treated liquid under 1.5 was added to the fermenter by feeding, wherein the feeding amount of the second molasses treated liquid was about 4000mL, the time for the second molasses treated liquid to reach the maximum flow rate was about 8h, and the maximum ventilation volume was reached after 6h. During the fermentation process, the pH value was controlled to gradually increase from 4 to 6.4, the fermentation temperature was controlled at 30°C, and the fermentation was terminated after 14h±0.4h.

[0117] Referring to the preparation method of yeast fermentation wastewater under 1.3, the obtained fermentation liquid was separated and washed to obtain yeast fermentation wastewater and yeast. The quality of the yeast was tested by referring to the detection method of Control Example 1 in 2.3.1. The results are shown in Table 6.

[0118] Table 6

[0119] Yeast index Test results Nucleic acid (dry basis) content (%) 8.5 Protein (dry basis) content (%) 65.67 Sugar conversion rate 78％～80％ Viable cell rate (%) ≥98 Total colony count (cfu / g) <![CDATA[≤1×10 4 ]]> Coliform group (MPN / g) ≤2

[0120] 2.3.6 Comparative Example 2 (fermentation bottom water includes 75 wt% condensed water, second molasses treatment liquid)

[0121] 1L of process soft water and 3L of condensed water under 1.4 were added to a 15L fermenter as fermentation bottom water, magnesium sulfate and zinc sulfate were added, the pH was adjusted to 4.0 with sulfuric acid, and sterilized at 121°C and 0.1Mpa for 30min. Vitamin B1 and biotin were added after cooling to 30°C, and 300mL of seed yeast milk cultured in 2.2 was inoculated, that is, about 225g of seed yeast was inoculated into the fermenter. At this time, the initial wet weight of the fermentation liquid was about 50g / L, and then fermentation was carried out. The second molasses treated liquid under 1.5 was added to the fermenter by feeding, wherein the feeding amount of the second molasses treated liquid was about 4000mL, the time for the second molasses treated liquid to reach the maximum flow rate was about 8h, and the maximum ventilation volume was reached after 6h. During the fermentation process, the pH value was controlled to gradually increase from 4 to 6.4, the fermentation temperature was controlled at 30°C, and the fermentation was terminated after 13h±0.4h.

[0122] Referring to the preparation method of yeast fermentation wastewater under 1.3, the obtained fermentation liquid was separated and washed to obtain yeast fermentation wastewater and yeast. The quality of the yeast was tested by referring to the detection method of Control Example 1 in 2.3.1. The results are shown in Table 7.

[0123] Table 7

[0124] Yeast index Test results Nucleic acid (dry basis) content (%) 8.25 Protein (dry basis) content (%) 63.1 Sugar conversion rate 73％～76％ Viable cell rate (%) ≥98 Total colony count (cfu / g) <![CDATA[≤1×10 4 ]]> Coliform group (MPN / g) ≤2

[0125] 2.3.7 Example 4 (fermentation bottom water includes 75 wt% condensed water, second molasses treatment liquid)

[0126] 1L of process soft water and 3L of condensed water under 1.4 were added to a 15L fermenter as fermentation bottom water, magnesium sulfate and zinc sulfate were added, the pH was adjusted to 4.0 with sulfuric acid, and sterilized at 121°C and 0.1Mpa for 30min. Vitamin B1 and biotin were added after cooling to 30°C, and 300mL of seed yeast milk cultured in 2.2 was inoculated, that is, about 225g of seed yeast was inoculated into the fermenter. At this time, the initial wet weight of the fermentation liquid was about 50g / L, and then fermentation was carried out. The second molasses treated liquid under 1.5 was added to the fermenter by feeding, wherein the feeding amount of the second molasses treated liquid was about 4000mL, the time for the second molasses treated liquid to reach the maximum flow rate was about 8h, and the maximum ventilation volume was reached after 6h. During the fermentation process, the pH value was controlled to gradually increase from 4 to 6.4, the fermentation temperature was controlled at 30°C, and the fermentation was terminated after 15h±0.4h.

[0127] Referring to the preparation method of yeast fermentation wastewater under 1.3, the obtained fermentation liquid was separated and washed to obtain yeast fermentation wastewater and yeast. The quality of the yeast was tested by referring to the detection method of Control Example 1 in 2.3.1. The results are shown in Table 8.

[0128] Table 8

[0129] Yeast index Test results Nucleic acid (dry basis) content (%) 8.47 Protein (dry basis) content (%) 64.9 Sugar conversion rate 78％～80％ Viable cell rate (%) ≥98 Total colony count (cfu / g) <![CDATA[≤1×10 4 ]]> Coliform group (MPN / g) ≤2

[0130] 2.3.8 Comparative Example 3 (fermentation bottom water includes 100 wt % condensed water, second molasses treatment liquid)

[0131] 4L of condensed water under 1.4 was added to the 15L fermenter as fermentation bottom water, magnesium sulfate and zinc sulfate were added, the pH was adjusted to 4.0 with sulfuric acid, and sterilized at 121°C and 0.1Mpa for 30min. Vitamin B1 and biotin were added after cooling to 30°C, and 300mL of seed yeast milk cultured in 2.2 was inoculated, that is, about 225g of seed yeast was inoculated into the fermenter. At this time, the initial wet weight of the fermentation liquid was about 50g / L, and then fermentation was carried out. The second molasses treated liquid under 1.5 was added to the fermenter by feeding, wherein the feeding amount of the second molasses treated liquid was about 4000mL, the time for the second molasses treated liquid to reach the maximum flow rate was about 8h, and the maximum ventilation volume was reached after 6h. During the fermentation process, the pH value was controlled to gradually increase from 4 to 6.4, the fermentation temperature was controlled at 30°C, and the fermentation was terminated after 13h±0.4h.

[0132] Referring to the preparation method of yeast fermentation wastewater under 1.3, the obtained fermentation liquid was separated and washed to obtain yeast fermentation wastewater and yeast. The quality of the yeast was tested by referring to the detection method of Control Example 1 in 2.3.1. The results are shown in Table 9.

[0133] Table 9

[0134]

[0135]

[0136] 2.3.9 Example 5 (fermentation bottom water includes 100 wt% condensed water, second molasses treatment liquid)

[0137] 4L of condensed water under 1.4 was added to the 15L fermenter as fermentation bottom water, magnesium sulfate and zinc sulfate were added, the pH was adjusted to 4.0 with sulfuric acid, and sterilized at 121°C and 0.1Mpa for 30min. Vitamin B1 and biotin were added after cooling to 30°C, and 300mL of seed yeast milk cultured in 2.2 was inoculated, that is, about 225g of seed yeast was inoculated into the fermenter. At this time, the initial wet weight of the fermentation liquid was about 50g / L, and then fermentation was carried out. The second molasses treated liquid under 1.5 was added to the fermenter by feeding, wherein the feeding amount of the second molasses treated liquid was about 3900mL, the time for the second molasses treated liquid to reach the maximum flow rate was about 8h, and the maximum ventilation volume was reached after 6h. During the fermentation process, the pH value was controlled to gradually increase from 4 to 6.4, the fermentation temperature was controlled at 30°C, and the fermentation was terminated after 15h±0.4h.

[0138] Referring to the preparation method of yeast fermentation wastewater under 1.3, the obtained fermentation liquid was separated and washed to obtain yeast fermentation wastewater and yeast. The quality of the yeast was tested by referring to the detection method of Control Example 1 in 2.3.1. The results are shown in Table 10.

[0139] Table 10

[0140]

[0141]

[0142] Tables 1 to 10 are summarized in Table 11.

[0143] Table 11

[0144]

[0145] It can be seen that: Example 1 is relative to Control Example 1, and the condensed water is directly used as the dilution water of molasses, which has no significant effect on the relevant indicators of yeast. Comparative Examples 1, 2, and 3 are relative to Example 1. As the amount of condensed water used directly as fermentation bottom water increases, the nucleic acid and protein indicators of yeast have a slightly downward trend, but the material indicators of protein, nucleic acid and viable cell rate are all within the required range (protein ≥ 60%, nucleic acid ≥ 8%, viable cell rate ≥ 98), and at the same time, the sugar conversion rate is significantly reduced. It is explained that after condensed water is directly used for fermentation bottom water, the greater the proportion of condensed water in the initial fermentation environment, the greater the impact on the subsequent material indicators (especially the conversion rate) of yeast. The possible reason is that the yeast proliferation rate in the early stage of fermentation is affected and reduced, the sugar consumption rate is slowed down, and the excess sugar is used to produce metabolic by-products. After the early adaptation, the effect of the condensed water used on the middle and late yeast is significantly weakened, so Examples 3, 4, and 5 can increase the nucleic acid and protein content and the sugar conversion rate by appropriately reducing the sugar supplement rate (extending the fermentation cycle and / or reducing the total sugar supplement amount), so that each indicator is basically close to the situation when condensed water is not used.

[0146] Furthermore, commercially available brewer's yeast was used for experiments, and it was found that yeast of ideal quality can be obtained by adjusting the fermentation time of the fermentation treatment process and / or the amount of molasses treatment liquid added. That is, the adverse effect on the yeast fermentation quality caused by directly reusing condensed water as fermentation bottom water and / or dilution water for molasses to the fermentation treatment process (especially directly using condensed water as fermentation bottom water) can be compensated by adjusting the fermentation time of the fermentation treatment process and the amount of molasses treatment liquid added.

[0147] In summary, the present invention simplifies the yeast fermentation wastewater treatment process (from multi-step simplification to evaporation concentration step) while maintaining the stable quality of yeast by adjusting the fermentation process, and increases the reuse amount of yeast fermentation wastewater in the fermentation treatment process (increases the use as fermentation bottom water, and increases the reuse amount by even about 2 times compared with the water used only for molasses dilution), thereby reducing wastewater discharge and process water, and saving costs. On the basis of realizing comprehensive resource utilization, a method combining multiple treatment technologies is adopted to ultimately achieve standard discharge and recycling of wastewater, and achieve the application effect of energy conservation and emission reduction.

[0148] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing yeast, characterized in that: The following steps are involved: Providing yeast fermentation wastewater, performing evaporation and concentration treatment on the yeast fermentation wastewater, and collecting condensed water; The yeast is fermented by using fermentation bottom water and molasses treatment liquid to obtain yeast; wherein the fermentation bottom water includes the condensed water, and the mass proportion of the condensed water in the fermentation bottom water is 25wt%~100wt%; the treatment method of the molasses treatment liquid includes using the condensed water to dilute the molasses until the total sugar concentration in the dilution liquid is 30wt%±0.1wt%, and 3800mL~4100mL of the molasses treatment liquid is added for every 220g~230g of seed yeast, and the molasses is sugarcane molasses; The process parameters of the fermentation treatment include: adjusting the fermentation time to 12h~16h so that the material index and material conversion rate of the obtained yeast meet the following conditions at the same time: The protein content accounts for no less than 60wt% of the yeast dry weight; the nucleic acid content accounts for no less than 8wt% of the yeast dry weight; the viable cell rate is ≥98%; the sugar conversion rate is ≥78%; The molasses treatment liquid is introduced by a feeding method, and the process parameters of the feeding include: a maximum flow rate of 350ml / h~450ml / h; The molasses treatment liquid is introduced by a feeding method, and the process parameters of the feeding include: the time to reach the maximum flow rate is 7h~9h; For every 220g~230g of seed yeast, add 4.1L~4.3L of the fermentation bottom water; The process parameters of the fermentation treatment include: controlling the ventilation volume of the fermentation system so that the maximum ventilation volume is 25L / min~30L / min, and the time to reach the maximum ventilation volume is 5h~7h; The process parameters of the fermentation treatment include: controlling the pH value of the fermentation system to be 4.0-6.5; The process parameters of the fermentation treatment include: the fermentation temperature is 28°C~34°C.

2. The method for preparing yeast according to claim 1, characterized in that: The steps of obtaining yeast fermentation wastewater include: The fermentation liquid obtained after the fermentation treatment is subjected to solid-liquid separation treatment and washing treatment to obtain yeast fermentation wastewater.

3. The method for preparing yeast according to claim 1, characterized in that: The evaporation concentration process is performed to a solid content of 50wt% to 60wt%.

4. The method for preparing yeast according to claim 1, characterized in that: The seed yeast is Saccharomyces cerevisiae.

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