Direct l-lactic acid fermentation with sago starch by a novel amylolytic lactic acid bacterium, Enterococcus faecium

Abstract

Novel amylolytic lactic acid bacterium from puto, fermented raw rice in Philippine, was isolated and characterized. The strain was identified as Enterococcus faecium No. 78 (BIOTECH 10375) by sugar fermentative test and 16S rDNA sequence analysis. Optimum pH and temperature were 6.5 and 30 °C, respectively. Direct l-lactic acid fermentation was carried out with various starches, lactic acid productivity with sago starch being similar to that with glucose. Yield of lactic acid from sago starch was higher than those from glucose and other starches. Strain No. 78 was superior to the other amylolytic lactic acid bacteria so far reported on the direct lactic acid fermentation with starches and produced lactic acid of high optical purity (98.6%). In direct lactic acid fermentation with starch, continuous culture has hardly been reported. Continuous culture system with high cell density of strain No. 78 showed higher lactic acid productivity (3.04 g l −1 h −1) than those of batch culture (1.105 g l −1 h −1) and conventional continuous culture (1.56 g l −1 h −1). Even if the dilution rate was increased up to 0.26 h −1, the residual starch concentration was controlled at moderately low level below 3.24 g l −1.