Of Nisin Fermentation Conditions Optimization And Metabolic Regulation

Nisin is a kind of Natural Food Preservative that is allowed to commercialized production. Nisin can inhabit most of the gram positive pathogenic bacteria. There are only a few company produce Nisin in china but the output and purity are lower than foreign contries. The purpose of this article is to analyze the metabolic process and regulation mechanism of Nisin by the method of fermentate condition optimization. CM media was selected as original medium from five lactic acide bacteria fermention mediums in this study. On the basis of this study, Nisin production of the best initial pH value of 7.0, the optimum amount of inoculation is 3%, the best inoculation age for 12h were explored.Subsequently, Nisin motablism was controlled by the method of nutritional manipulation, amino acid metabolic regulation and lactic acid feedback regulation. By nutritional manipulation method, maize liquid was select as nitrogen source and KH2PO4 as phosphorus source to fermentation. Then by Plackett-Burman tests, three main factors impact of Nisin titer is sucrose, yeast extract and the concentration of KH2PO4. By Box-Behnken test analysis, the best concentration of the three main factors for fermentation were 39g/L, 18.5g/L and 20.5g/L. Optimization of the medium after fermentation Nisin efficiency at 1687±5IU, increased 740 IU/mL.Through the regulation of amino acids, Arg, Cys and Trp have positive regulation on Nisin. When added 1g/L Arg, Cys and Trp ,the potency was increased by 224±5IU/mL, 130±5IU/mL and 118±5IU/mL, and 1 g/L of Pro Nisin play a negative role in regulation to Nisin potency, which make it reduce by 138±5IU/mL. Lactococcus lactis in extension of demurrage-free use of a large number of amino acids, into the growing number of decomposition, the nitrogen source of decomposed protein was mainly used. Lactococcus lactis tests proved that the use of relying mainly on the surrounding environment from the absorption in the Arg, rather than self-synthesizing. Consumption of arginine was the largest in the process of Nisin metabolism, with the increase of arginine, output amount of Nisin increased, but the rate of increase was low. When the amount of arginine was 8 g/L, production of Nisin no longer increased.Finally feedback control of lactic acid was studied in the article. By calculating, conversion rate of process saccharose into lactic acid metabolism in fermentation was 83.3%. Due to the decline of pH and lactic acid accumulation, inhibition occured. Feded by 5 M NaOH, broth pH was control around 7.0, on the basis of optimization fermentation, production of Nisin in the medium raised 420±5IU/mL. When content of lactic acid root in fermentation was 7%, production of Nisin was stopped and it was concluded that the the accumulation of lactic acid root was the limit factor for equalizing-sugar fermentation.After optimization conditions of culture and metabolic control, potency of Nisin increased nearly 1410 IU/mL, about 1.5 times for non-regulation and control.