Research On Screening And Fermentation Optimization Of Lactobacillus Os High-Yielding EPS

Pueraria is a traditional medicinal materials about anti-inebriation, witn good results in promoting alcohol meTableolism. Yoghourt can protect membrane of the stomach and reduce the stimulus from alcohol. And its rich amino acids can effectively regulate meTableolic disturbance in the body resulting from alcohol meTableolism. Second, exopoly saccharides in yoghourt can promote the clearance of free radicals coming from alcohol meTableolism , with its antioxidation.In this paper, we separate a strain of lactobacillus from yoghourt , which is of high-yielding EPS, and then use the pueraria and skim milk as basic material for fermentation of the lactobacillus, and we also suty its fermentation process. In the end, we obtain a kind of fermenting pueraria radix- yoghourt rich of total flavones and EPS, which is nourishing, delay the absorption of alcohol and promote alcohol meTableolism, and clear free radicals coming from alcohol meTableolism and regulate meTableolic disturbance in the body resulting from alcohol meTableolism. The main results are as follows:(1) Using medium with bromocresol purple, we screen preliminarily some strains of lactobacillus from yoghourt, which are of high-yielding EPS.And then we identify the genus and species of the strains, following the Berger bacterial identification manual and physiological and biochemical characteristics of lactobacillus. The identification results are that: Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius. thermophilus.(2) Through single factor and comparison experiments, we determinded the main materials, proportion and initial pH of medical medium:low-temperature baked pueraria and skimmed milk powder, the proportion between12% saccharification liquid of pueraria and 12% skim milk is 2:1, the initial pH is greater than 6.28; And we determinded the favorable strain for fermentation is Streptococcus salivarius. thermophilus, the growth curve of which is that:lag phase is in 0-5h; logarithmic phase in 5-16h; stationary phase is in 16-20h. And the entire growth cycle of about 30 hours. We also found that, within a certain range, the content of saccharification liquid of pueraria is higher, the growth of Streptococcus salivarius. thermophilus is better.(3)Using single-factor method and response surface method, we optimized conditions of fermentation for Streptococcus salivarius. thermophilus. And the we regression analyse the response value by SAS9.2 statistical software. We determinded the best conditions of fermentation for Streptococcus salivarius. thermophilus: fermentation temperature is 38.7℃; cultivation time is 19.8 hours; glucose addition level is 1.38%. And the content of total flavones reached to 1.91 mg / ml, and EPS content reached to 0.155 mg / ml.