초록
<P>Lactic acid is one of the top 30 potential building-block chemicals from biomass, of which the most extensive use is in the polymerization of lactic acid to poly-lactic-acid (PLA). To reduce the cost of PLA, the search for cheap raw materials and low-cost process for lactic acid production is highly desired. In this study, the final titer of produced L-lactic acid reached a concentration of 185 g·L<SUP>−1</SUP> with a volumetric productivity of 1.93 g·L<SUP>−1</SUP>·h<SUP>−1</SUP> by using sugarcane bagasse hydrolysate as the sole carbon source simultaneously with cottonseed meal as cheap nitrogen sources under the open fed-batch fermentation process. Furthermore, a lactic acid yield of 0.99 g per g of total reducing sugars was obtained, which is very close to the theoretical value (1.0 g g<SUP>−1</SUP>). No D-isomer of lactic acid was detected in the broth, and thereafter resulted in an optical purity of 100%, which exceeds the requirement of lactate polymerization process. To our knowledge, this is the best performance of fermentation on polymer-grade L-lactic acid production totally using lignocellulosic sources. The high levels of optically pure <SMALL>L</SMALL>-lactic acid produced, combined with the ease of handling and low costs associated with the open fermentation strategy, indicated the thermotolerant <I>Bacillus</I> sp. P38 could be an excellent candidate strain with great industrial potential for polymer-grade L-lactic acid production from various cellulosic biomasses.</P>