High Temperature Production Of Lactic Acid From Lignocellulose

Lactic acid is an important platform chemical that is widely used in food,cosmetics,pharmaceuticals,chemical industry and agriculture,especially in the synthesis of biodegradable polylactic acid.However,its applications are limited due to the high cost of carbon and nitrogen sources.Therefore,it is important to explore alternative cheap material for lactic acid production.Lignocellulose waste,the most abundant and renewable biomass resource,is considered as economically attractive alternative substrates for reducing the cost of biomanufacturing.In this study,lactic acid fermentation by thermophilic strains with lignocellulose was systematically investigated.This study provides an economical and efficient alternative for the production of lactic acid using lignocellulose.The main work is as follows:(1)L-Lactic acid production by thermophilic Bacillus coagulans strains through simultaneous saccharification and fermentation of microcrystalline cellulose was systematically investigated.Cellulases obtained from various commercial sources,Bacillus coagulans strains,the alternative cheaper source for carbon and nitrogen,substrate and enzyme concentration were evaluated.(2)L-Lactic acid production by Bacillus coagulans H-1 through simultaneous saccharification and fermentation of lignocellulosic corncob residue(CCR)was investigated.Under the optimal conditions,batch and fed-batch fermentations were performed.Our results reveal that 68.0 g/L L-lactic acid was obtained with a high yield of 0.85 g/g cellulose by B.coagulans strain H-1 after 36 h in batch fermentation.B.coagulans H-1 with SSF of CCR showed relatively high yield and productivity of L-lactic acid.The study shows that B.coagulans H-1 could be an attractive producer of L-lactic acid and attractive lignocellulosic wastes such as CCR could be used in the efficient biomanufacture of L-lactic acid.(3)Endoglucanase gene was expressed into Bacillus licheniformis BN11 strain for one-step production of D-lactic acid from amorphous cellulose.Four thermophilic neutral endoglucanase genes from different sources were evaluated.Finally,promoter and signal peptide were optimized for the gene expression.