Production of L-lactic acid from a mixture of xylose and glucose by co-cultivation of lactic acid bacteria.
The production of optically pure lactic acid in a high yield from xylose or a mixture of xylose and glucose, which is a model hydrolysate of lignocellulose, is described. In a single cultivation, Enterococcus casseliflavus produced 38 g/l of lactic acid with an optical purity of 96% enantiomeric excess (ee) and 6.4 g/l of acetic acid from 50 g/l of xylose when MRS medium was used. When a mixture of 50 g/l of xylose and 100 g/l of glucose was used as the carbon source in a cultivation of E. casseliflavus alone, glucose was converted to lactic acid in the early phase of the cultivation but xylose was hardly consumed. In a co-cultivation where E. casseliflavus and Lactobacillus casei specific for glucose were simultaneously inoculated, little or no lactic acid was produced after the glucose was almost consumed. A co-cultivation with two-stage inoculation (in which E. casseliflavus was added at a cultivation time of 40 h after L. casei cells were inoculated) resulted in complete consumption of 50 g/l of xylose and 100 g/l of glucose. In the co-cultivation, 95 g/l of lactic acid with a high optical purity of 96% ee was obtained at 192 h. Such a co-cultivation using two microorganisms specific for each sugar is considered to be one promising cultivation technique for the efficient production of lactic acid from a sugar mixture derived from lignocellulose.
Taniguchi
M
M
Faculty of Engineering, Department of Materials Science and Technology, Niigata University, Ikarashi 2, Niigata, 950-2181, Japan. mtanig@eng.niigata-u.ac.jp
Tokunaga
T
T
Horiuchi
K
K
Hoshino
K
K
Sakai
K
K
Tanaka
T
T
D018920:Coculture Techniques; D003470:Culture Media; D005285:Fermentation; D005947:Glucose / Q000378:metabolism*; D019344:Lactic Acid / Q000096:biosynthesis* / Q000378:metabolism; D007778:Lactobacillus / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*
D003470:Culture Media; D019344:Lactic Acid; D014994:Xylose; D005947:Glucose