Abstract
Clostridium bifermentans strains, isolated from a manure, were examinated for their ability to produce lactic acid from PY medium with glycerol under different pH conditions and when PY medium was supplemented with saccharides such as fructose, sorbitol, glucose, mannose, mannitol, maltose, xylose, raffinose, and arabinose. In the last test performed, the ability of investigated strains to produce lactic acid from mixed carbon source (glycerol plus saccharide) was checked. The strains of Cl. bifermentans, designated as CB 371, CB 374, and CB 376 grew and produced lactic acid on PY medium irrespective of pH and the carbon source used. The optimal lactic acid production on PY medium with glycerol was obtained at pH of 7.0 in case of CB 371 and 376 (19.63 g/L and 16.65 g/L, accordingly) and at pH 8.0 in case of CB 374 (13.88 g/L). The best productivity of lactic acid on PY media by CB 371, CB 374, and CB 376 (above 30 g/L) was observed when mannitol was used as a carbon source. The mixed carbon source did not increase productivity of lactic acid by Cl. bifermentans. The yield of lactic acid was approximately equal to the yield of lactic acid obtained on the medium with only glycerol and lower than in medium with only mannitol. Thus, from the environmental point of view it is more beneficial to use the medium with waste-type material only, such as glycerol.