Mutagenesis In Lactobacillus Pentosus And Research Of Lactic Acid Fermentation By Popolar Wood

lactic acid and its derivatives can be widely used in food, chemical industry, textile industry, curriery, electronics, medicine,agriculture and many other areas,it gets extensive market demand.when lactic acid polymerize,it synthesized PLA.PLA can made into PLA-plastics, which can solve the increasingly serious environmental pollution problems.The research in the field of PLA attracted worldwide attention.In our country,the content of lignocellulose is very rich. Using ignocellulose as raw material to produce lactic acid great significance in saving food, environmental protection and promoting the development of lactic acid industry.This study obtain mutated strains of high lactic acid productivity by ultraviolet mutating lactobacillus pentosus ATCC8041; optimization of lactic acid production medium and fermentation conditions; fermentation of poplar fiber hydrolysate. The main results are as follows:(1)Optimization of lactic acid production medium condition and fermentation conditions of lactobacillus pentosus ATCC8041.First, the effect of glucose, Peptone, yeast extract, Na2HPO4·12H2O, MgSO4, MnSO4, CaCO3 concentration on produced lactic acid was studied. Plackett-Burman design was used to evaluate the effects of seven medium components on the production of lactic acid by lactobacillus pentosus ATCC 8041,which showed that glucose and yeast extract was the most significant ingredients (P<0.05). Second, by Box-Behnken the optimum fermentation medium was studied.The result showed that the optimum fermentation medium were as followed:glucose 93.11 g/L, yeast extract 5.19 g/L, CaCO329.43 g/L, Peptone 10.00g/L, Na2HPO4·12H2O 5.00g/L, MgSO4 0.20g/L,MnSO450mg/L. Under this condition, the yield of lactic acid can be up to 54.11 g/L. Which get a high correlation with predicted values.At last,a better fermentation conditions of lactobacillus pentosus ATCC8041 was studied by single factor experiment.(2)Breeding of high lactic acid yield mutated strains, lactobacillus pentosus ATCC 8041 The protoplasts treated by UV light for certain. The mutated strains were selected by plate method and shake flasks fermentation and obtained a high-yield strains lactobacillus pentosus lacticUVC-02,and hereditary of lacticUVC-02 has a good stability.The yield of lactic acid produced by mutant lacticUVC-02 were 64.17 g/L, which were 18.84% higher than the original strain.(3)The preliminary study of production of lactic acid by simultaneous saccharification and fermentation use slag of steam blasting poplar, a better hydrolyzation conditions of Youtell cellulase was studied by single factor experiment, Based on the optimization of fermentation medium, use steam blasting poplar substitute glucose, add 15FPU/g cellulase, take SSF fermentation. By orthogonal design of experiment, the optimum fermentation conditions of SSF were as followed: fermentation temperature 45℃, initial pH 5.7, inoculums volume 6%. Under those conditions, the yield of lactic acid produced by mutant lacticUVC-02 were 9.42g/L, which were 83.62% higher than before, that provided some references for fermentation experiment.