Optimization Of Fermentation Process For Lactic Acid From Popolar Wood Fiber

Lactic acid is recognzed as one of the three organic acids in the world,which has a great of potential market.With,the growing demand for lactic acid and its derivatives,people pay more and more attention to the materials and methods of production of lactic acid.Lignocellulose is rich and cheap renewable resource in the world.Using lignocellulose as raw material to produce lactic acid has great significance in reducing material cost,saving food and reducing environmental pollution.The laboratory obtain mutated strains named LacticUVC-02 of high lactic acid productivity by ultraviolet mutating lactobacillus pentosus ATCC8041,this study optimized the fermentation process for lactic acid from poplar wood by LacticUVC-02,the main results are as follows:(1)Optimization of lactic acid production medium condition and fermentation conditions of LacticUVC-02 by separate hydrolysis and fermentation.First,the effect of inoculums volume,shaking speed,different additive,concentration of additive,phosphate sources,concentration of phosphate,nitrogen sources,concentration of nitrogen,the way of adding CaCO3 on produced lactic acid was studied.Plackett-Burman design was used to evaluate the effects of five factors on the production of lactic acid by LacticUVC-02,which showed that beef extract,tween-20 and KH2PO4 was the most significant ingredients(P<0.05).Second,by Box-Behnken the optimum fermentation medium and conditions was studied as followed:beef extract 16.59g/L,Tween-20 2.18g/L,KH2PO4 8.07g/L,inoculums volume 10%,shaking speed 120r/min,add 5g CaC03 in every 12h.Under this condition,the yield of lactic acid can be up to 32.56g/L.Which get a high correlation with predicted values;(2)By orthogonal design of experiment,the primary and secondary order of four factors that effect lactic acid fermentation production by simultaneous saccharification and fermentation are as follows:temperature>PH>enzyme>inoculums volume;the optimum fermentation conditions of SSF were as followed:temperature 45℃,PH 5.8,inoculums volume 8%,enzyme 15FPU/g,the best way of adding enzyme is that 10FPU/g before fermentation,then 5FPU/g after 48h,after 12h of enzymolysis then adding lactobacillus is the best time.Under those conditions,the yield of lactic acid produced by mutant LacticUVC-02 were 17.45g/L.(3)Optimization of the amplification verified by fermentation tank on the basis of the optimization of shake flask by SSF,the yield of lactic acid produced by LacticUVC-02 was 17.20g/L.Optimization of lactic acid fermentation process with fermentation tank in SSF by orthogonal design of experiment.Under the optimization,the yield of lactic acid produced by mutant LacticUVC-02 was 21.02g/L,which improved 22.21%.The optimization provides a theoretical basis for putting into industrial production.