초록
<P>A few strains of lactic acid bacteria metabolise xylose into optically pure l-lactic acid (LA). This study achieved an effective homofermentative cell recycle continuous fermentation of xylose to l-LA with high concentration, productivity, and yield using <I>Enterococcus mundtii</I> QU 25. In conventional continuous fermentation, the optimal xylose concentration in the feeding solution is 50 g L<SUP>−1</SUP>, and the optimal dilution rate is 0.15 h<SUP>−1</SUP>. Continuous fermentation with cell recycling using a microfiltration membrane module produced an l-LA concentration of 32.3 g L<SUP>−1</SUP> with a yield of 0.789 g g<SUP>−1</SUP> and a productivity of 5.33 g L<SUP>−1</SUP> h<SUP>−1</SUP>. Controlling pH and optimising the feeding medium were important for achieving a high l-LA yield with strain QU 25. Using corn steep liquor-containing medium at pH 6.2, a maximum l-LA concentration, yield and productivity were achieved at 41.0 g L<SUP>−1</SUP>, 1.01 g g<SUP>−1</SUP>, and 6.15 g L<SUP>−1</SUP> h<SUP>−1</SUP>, respectively. This study is the first to report on continuous fermentation with cell recycling for lactic acid production from xylose.</P>