RU1243354C - Method of obtaining lactic acid - Google Patents

Description

 The invention relates to the food industry, and in particular to methods for producing lactic acid based on microbiological synthesis by a continuous method.

 The purpose of the invention is to increase the yield of the target product and reduce the duration of the process.

Maintaining during the fermentation process a certain density of the lactic acid bacteria population in the first fermentation apparatus (18 ⁸ 10 ^{8 20} ˙ 10 ⁸ cells in 1 ml of medium) due to the recirculation of the fermented solution from the second fermentation apparatus, as well as the continuous influx of fresh nutrient medium, ensure the active physiological state of the lactic acid bacteria with the maximum ability of lactic acid biosynthesis.

Conducting a fermentation process with a recirculation coefficient of less than 0.4 and a dilution rate of fermented with fresh nutrient medium less than 0.05 h ^-1 does not provide the required population density of lactic acid bacteria, as a result of which the process slows down and approaches a periodic mode.

 Using a recirculation coefficient of more than 0.6 does not significantly improve the technological parameters of the fermentation process and is economically irrational.

The implementation of the lactic acid fermentation process with a dilution rate of the fermented medium is more than 0.07 h ^-1 leads to a decrease in the population density of lactic acid bacteria and an increase in the duration of fermentation. With a subsequent increase in the rate of dilution of the medium, the fermentation process stops due to the complete leaching of lactic acid bacteria.

When conducting the fermentation process while maintaining the population density of lactic acid bacteria in the first fermenter, less than 18 ˙ 10 ⁸ cells in 1 ml of medium, the duration of fermentation increases, since young cells with less acid-forming ability predominate in the population. Maintaining a population density of lactic acid bacteria in the first fermentation apparatus at a level of more than 20 ˙ 10 ⁸ cells per 1 ml of medium is impractical, since their growth rate is reduced due to the high density of the bacterial population.

Sugar-containing solution is prepared from beet molasses, molasses and raw sugar in a ratio of 1: 2: 7 (Technological instruction for the production of food lactic acid TI 18-8-1-83, L. 1983), heated to 85-90 ^o C, incubated for at least 1 h, cooled to 48-50 ^o C.

During fermentation, the content of lactic acid in the medium is maintained at a level of 0.3-0.5%. With a lactic acid content of less than 0.3%, there is a danger of the appearance of extraneous microflora in the fermented solution, with a content of more than 0.5%, the vital activity of lactic acid bacteria is inhibited and the biosynthetic activity of bacteria decreases. The lactic acid formed during fermentation in each apparatus is continuously neutralized with calcium carbonate, automatically feeding it in the form of chalk milk with a density of 1.13-1.16 g ˙ cm ^-3 , thereby maintaining the pH of the fermented solution at the level of 5.0-5.3 .

The fermentation process ends in the fourth fermenter after 3-4 days when the content of calcium lactate is 14-15% and sugar 0.1-0.5%. The yield of lactic acid at the fermentation stage is 86.5%.
PRI me R 1. Fermentation of a sugar-containing solution consisting of beet molasses, refined molasses and raw sugar in a ratio of 1: 2: 7, lactic acid bacteria L. delbruDotDotckii strain L-3 is carried out by a continuous method in a flowing medium in four fermenters with a capacity of 3 l each, connected in series to the battery using overflow pipes.

Sugar-containing medium (2 L) with a content of 8-10% sugar heated to 85-90 ^{° C,} held for at least 1 hour and cooled to 48-50 ^C. At this temperature, the medium is made of 0.6-0.9 liter one-day cultures of lactic acid bacteria, 54-60 g of malt sprouts and are fermented in the first fermenter. The lactic acid formed in the fermented solution is continuously neutralized with potassium carbonate in the form of chalk milk with a density of 1.13-1.16 g˙ cm ^-3 , converting it to calcium lactate. When a population density of lactic acid bacteria is reached in the fermented medium 18 ^. 10 ⁸ cells in 1 ml of the solution, the content of calcium lactate 4-5% and sugar 5-6% begin a continuous influx of fresh sugar-containing medium with a concentration of 12-13% from the pressure vessel into the first fermentation apparatus. Upon reaching the level of the overflow pipe, an excess amount of the solution flows through it into the second fermentation apparatus. When the second apparatus is filled, the solution flows into the third apparatus, and then from the third to the fourth apparatus. Thus, the volume of fermented solution in each apparatus is maintained at a constant level. Sugar-containing medium is fed through a metering device at a speed corresponding to the dilution rate of the fermented solution, 0.05 h ^-1 . The fermentation process is carried out with a recirculation coefficient of 0.4 and a population density of lactic acid bacteria 18 ^. 10 ⁸ cells in 1 ml of medium with continuous introduction of malt sprouts in an amount of 20-25 g ˙l ^-1 ˙h ^-1 for four fermentation apparatus. The lactic acid formed during fermentation is continuously neutralized with calcium carbonate in the form of chalk milk with a density of 1.13-1.16 g ˙ cm ^-3 , while maintaining the pH of the fermented solution at the level of 5.0-5.3.

 The results of the experiments are presented in the table.

 The average duration of fermentation is 83 hours; the yield of lactic acid at the fermentation stage is 87.7% of the theoretically possible yield.

 PRI me R 2. The composition of the sugar-containing medium, its preparation, cultivation conditions of lactic acid bacteria and continuous fermentation are similar to those described in example 1.

Sugar-containing medium is supplied from the pressure vessel to the first fermentation apparatus at a speed corresponding to the dilution rate of the fermented solution, 0.06 h ^-1 . The fermentation process is carried out at a recirculation coefficient of 0.5 and a population density of lactic acid bacteria of 19 ˙ 10 ⁸ cells in 1 ml of medium. The results of the experiments are presented in the table.

 The duration of fermentation is on average 69 hours, the yield of lactic acid at the fermentation stage is 86.5% of the theoretically possible yield.

 PRI me R 3. The composition of the sugar-containing medium, its preparation, cultivation conditions of lactic acid bacteria and continuous fermentation are similar to those described in example 1.

Sugar-containing medium is supplied from the pressure vessel to the first fermentation apparatus at a speed corresponding to the dilution rate of the fermented solution of 0.07 h ^-1 . The fermentation process is carried out with a recirculation coefficient of 0.6 and a population density of lactic acid bacteria of 20 ⁸ 10 ⁸ cells in 1 ml of medium. The results of the experiments are presented in the table.

 The duration of fermentation is 69 hours, the yield of lactic acid at the fermentation stage is 85.3% of the theoretically possible yield.

Claims (1)

METHOD FOR PRODUCING LACTIC ACID, including continuous fermentation of a sugar-containing nutrient medium with lactic acid bacteria Lactobacillus delbruckii in a flow mode in a battery of series-connected fermentation apparatus, neutralization of the resulting lactic acid with calcium carbonate and its subsequent isolation, characterized by the fact that, in order to increase the yield and increase the yield and increase the yield process, when the population density of lactic acid bacteria in a first fermentor in the range of (18 20) 10 ⁸ millstands to 1 ml medium circulate the fermentation medium from the second into the first fermenter with recycling ratio of 0.4 0.6 at a dilution rate of fresh nutrient medium 0.05 0.07 hours ^{- 1}

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