Abstract
The formation of ketopentoses from aldopentoses was demonstrated by six strains of heterofermentative lactic acid bacteria (heterofermenters). The dried bacterial cells harvested on malt extract and their cell-free extracts were found to reveal isomerization of D-xylose or L-arabinose to corresponding ketopentoses in the presence of borate, while any formation of ketopentose was never observed with the enzyme preparations of homofermenters except L. xylosus and Pc. lindneri. The ketopentoses were isolated by a Dowex-l borate column, and identified by paperchromatography. Results obtained were as follows: xylulose was formed from xylose by six strains of heterofermenters (L. fermentum, Leuc. mesenteroides, L. brevis, L. buchneri, L. gayonii and L. Jermenti) and by L. xylosus. Ribulose was obtained from arabinose by L. brevis, L. pentoaceticus, L. gayonii, L. buchneri and Pc. linderi.
