Lactic acid production and carbon catabolite repression from single and mixed sugars using Enterococcus faecalis RKY1

Enterococcus faecalis RKY1, a newly isolated lactic acid bacterium, efficie ntly metabolized glucose, fructose, and maltose to lactic acid by the homol actic fermentation pathway through Embden-Meyerhof glycolysis. During lacti c acid fermentation with glucose, fructose, or maltose as a sole carbon sou rce, the average volumetric productivities. were 3.56, 4.12, and 3.54 g/lit re/h with final lactic acid concentrations of 139, 144, and 138 g/litre, re spectively. Furthermore, for the lactic acid fermentations with glucose/fru ctose, glucose/maltose, and fructose/maltose mixtures as carbon sources, En terococcus faecalis RKY1 grown on a mixture of glucose/fructose simultaneou sly consumed these sugars, and the cell growth and average volumetric produ ctivity were higher than when grown on the individual sugars. However, it p referentially metabolized the glucose and fructose in the glucose/maltose a nd fructose/maltose mixtures. Therefore, carbon catabolite repression on it s maltose metabolism was triggered by these preferentially metabolized suga rs. (C) 2001 Elsevier Science Ltd. All rights reserved.