Method for producing L-lactic acid through biomass fermentation

The invention discloses a method for producing L-lactic acid through biomass fermentation. The method comprises the following steps: after the biomass is subjected to alkaline liquid heat treatment, performing solid-liquid separation to obtain a liquid I and residues II; adding a culture medium containing the residues II into a saccharification fermentation tank, adding a cellulose degradation enzyme and performing a hydrolysis reaction for 0.5-6 hours at 50-55 DEG C; keeping the temperature of the saccharification fermentation tank at 50-55 DEG C; adjusting the pH value of the culture medium to 6.0-6.5 by using the liquid I; inoculating bacillus coagulans into the saccharification fermentation tank; and performing synchronous saccharification fermentation on the residues II for 48-96 hours in an anaerobic condition to produce L-lactic acid, and adding the liquid I in flow to keep the pH value of the fermentation liquid at 5.2-5.8. Compared with the prior art, the method disclosed by the invention not only can improve the comprehensive efficiency of converting cellulose and hemicellulose into lactic acid, and adopts an alkaline waste liquid to neutralize lactic acid in the fermentation process so as to reduce alkali consumption and waste water discharge in the lactic acid production industry.