Assimilation of glycerol by a strain of Lactobacillus collinoides isolatedfrom cider

A collection of glycerol-degrading lactic acid bacteria from spoiled cider was isolated The most widespread species was Lactobacillus collinoides, a h eterofermentative species which mainly produced the D-lactic acid isomer fr om glucose. Conditions of glycerol assimilation by such bacteria were inves tigated for strain tb, collinoides IOEB 9527 It could not be cultivated wit h glycerol alone as carbon source. Sugars were necessary for growth, and fr uctose was preferred to glucose. Glycerol was degraded, mainly to 1,3-propa nediol Small amounts of acrolein, produced from 3-hydroxypropion-aldehyde ( 3-HPA) during distillation of samples, were detected When Lb, collinoides w as cultivated with glucose or fructose alone, it produced the usual compoun ds of the heterofermentative pathway, notably D-lactic acid and small amoun ts of L-lactic acid, acetic acid and ethanol. When glycerol was present, th e amounts of lactic acid were surprisingly much lower and acetic acid + eth anol much higher than expected Oxidation of D-lactic acid, and to a lesser extent of L-lactic acid, was coupled to degradation of glycerol to 1,3-prop anediol This co-metabolism leading to acetic acid provided energy. Conseque ntly, in fermented beverages spoiled by such strains, glycerol is degraded and 3-HPA plus acetic acid are produced Both components are undesirable for health and sensorial qualify. (C) 2000 Academic Press.