Identification Of BCS 13002 And Simultaneous Saccharification And Fermentation Of High Optical Purity Of L-lactic Acid And Proteomic Research

Lactic acid has two isomers.L-lactic acid can be metabolized in body but its isomeride,D-lactic acid,cannot.High optical purity L-lactic acid can be used to food,biology,medicine,chemistry,etc,like biodegradable plastic and artificial skeleton.So it is hotspot to screen a new stain to produce high optical purity and research the theory about fermentation process.In this work,a bacillus produce high optical purity L-lactic acid screened out from fermented picklewas identified.We optimized the culture mediums and process about simultaneous saccharification and fermentation.At least,we compared the protein expression difference between four carbon sources.This strain was identified by 16 S rDNA gene sequence,microscopy,physiological and biochemical characteristics.It was namedBCS 13002.BCS 13002 got into stable phase about 6 h.It could invert glucose and corn starch hydrolysate to L-lactic acidwhich optical purity was larger than 99.8%.We compared the influence of nutrogens,carbon sources and neutralizers on L-lactate produced by BCS 13002.It is the best way to use yeast extract as nitrogen sourse,glucose as carbon sourse and NaOH as neutralizer.MgCl2、MnSO4contributedto improve L-lactic acid productivity.After response surface optimizing,we confirmed the culture medium is 46 g/L glucose,0.4 g/L MgCl2·6H2O,0.7 g/L MnSO4·H2O,10 g/L peptone,25 g/L yeast extract.The corn starch was hydrolyzed byα-amylase.115.86 g/L L-lactate was produced by glucose in batch.Invert ratio was 82.31 %.123.3 g/L L-lactate was produced by corn starch in SSF.Invert ration was 70.03 %.Comparing the differential expression protein about BCS 13002 fermented L-lactic acid with four carbon sources.A total of 328 proteins were detected as differentially expressed protein.We found BCS 13002 convert glucose and corn starch hydrolysate by EMP.The amylase from BCS 13002 took part in hydrolysaing corn starch.Meanwhile,BCS 13002 convert xylose and corn starch to acetic acid through other metabolism.We found formic acid invert to CO2 result in lower invert ratio in SSF with corn starch.