Xylooligosaccharide fermentation with Leuconostoc lactis

Strains of Leuconostoc lactis SHO-47 and Le. lactis SHO-54, producing the clinically useful enzyme NAD-specific 6-phosphoglucanate dehydrogenase, were cultivated with a hydrolyzed birch wood xylan as the unique carbon source to produce D-lactic acid for poly(D-lactic acid). In addition to the strains SHO-47 and SHO-54, Lactococcus lactis IO-1, well known as a good xylose-utilizing lactic acid bacterium, was used as a control to confirm the extent of hemicellulose hydrolysis. The fermentation time for lactic acid of strains SHO-47 and SHO-54 was 12 h, and produced respectively 2.3 and 2.2 g/l lactic acid from 8.5 g/l hydrolyzed xylan, whereas the fermentation time of strain IO-1 was 21 h, and produced 1.3 g/l lactic acid. Xylooligosaccharides from xylobiose to xylohexose were utilized more rapidly than xylose in the cultures of strains SHO-47 and SHO-54. However, xylose concentration increased temporarily and then decreased in the culture of strain IO-1. On the other hand, xylooligosaccharides larger than xyloheptaose were not utilized by these three strains. The xylosidase activities of SHO-47, SHO-54, and IO-1 were induced by xylose or a mixture of xylobiose and xylotriose. The xylosidases of these three strains were localized in their cytoplasm.