Study On The Optimization Of Propionic Acid Fermentation Process

The production of propionic acid by microbial fermentation has attracted extensive attention.This paper focuses on the large-scale fermentation of propionic acid industry.Through the study of step-by-step amplification process parameters,a process with good economic efficiency and direct application to propionic acid industrial production was finally established.The main research results of this paper are as follows:1.comparison of different Propionibacterium fermentation processesThe results showed that the propionic acid production of Propionibacterium fischeri and Propionibacterium acidogenes were 36.78 g·L^-1 and 37.41 g·L^-1respectively after 168 h fermentation in shake flask,and that of 7 L fermentation tank was increased to 42.10 g·L^-1 and 41.79 g·L^-1 respectively.Therefore,the fermentation level of the two Propionibacterium strains is equal.Considering the co production of propionic acid and vitamin B₁₂,it is more economical to replace Propionibacterium acidophilus with Propionibacterium fischeri.2.Direct fermentation to produce calcium propionate and vitamin B₁₂The main form of propionate production by fermentation is calcium propionate.From the point of view of atom and economy,calcium hydroxide is used to adjust the pH value during the co production of propionate?calcium?and vitamin B₁₂ by Propionibacterium freundii.The results showed that the yield of propionic acid was38.81 g·L^-1,vitamin B₁₂2 was 10.52 mg·L^-1,the yield of propionic acid was 40.02 g·L^-1,vitamin B₁₂ was 12.06 mg·L^-1,and the yield of propionic acid was 45.83 g·L^-1,vitamin B₁₂ was 12.57 mg·L^-1 in 150 L fermentor for 144 h.The above results are equivalent to the fermentation level of adjusting pH with ammonia water.Therefore,calcium hydroxide is used to adjust pH in the fermentation process of Propionibacterium fischeri,which can not only realize the co production of propionic acid?calcium?and vitamin B₁₂,but also reduce the use of ammonia water and production cost.3.Effect of carbon source on Fermentation of Propionibacterium fischeriWhen glucose was used as the sole carbon source to produce propionic acid,lactic acid was produced with the content of 39.63 g·L^-1.In order to reduce the production of lactic acid and other heteroacids and improve the conversion rate of sugar and acid,the effects of glucose and glycerin as the sole carbon source and the mixed carbon source on the fermentation process were analyzed,and the proportion and dosage of carbon source were optimized.The results of 150 L fermentation showed that when the glucose/glycerol ratio in the initial medium was 1:1 and the glucose/glycerol ratio in the carbon source was 2:1,the yield of propionic acid and vitamin B₁₂ were 57.95 g·L^-1 and17.53 mg·L^-1,respectively,the corresponding yields were 0.40 g·L^-1·h^-1 and 0.12 mg·L^-1·h^-1,respectively,and no lactic acid was produced.Therefore,the optimized carbon source can effectively control the production of heteroacids in the fermentation process.4.Establishment of pilot scale fermentation process of Propionibacterium fischeriThe results showed that the fermentation period was 144 h,the yield of propionic acid and vitamin B₁₂ were 66.64 g·L^-1 and 16.91 mg·L^-1,respectively,and the corresponding yields were 0.46 g·L^-1·h^-1 and 0.11 mg·L^-1·h^-1.Without affecting the output of vitamin B₁₂,the yield of propionic acid increased by 45.31%,the conversion of substrate increased by 71.87%,and the yield of heteroacids?lactic acid,succinic acid,acetic acid?decreased by 37.55%.The crude calcium propionate product with the content of 69.74%was prepared by concentrating,decolorizing and drying the fermentation liquid.