Lactic acid and hydrogen peroxide production by free and immobilization cells of two Lactococcus lactis subsp. lactis in a sugar molasses medium

Abstract

Natural, solid and porous support named pouzzolane was used for two Lactococcus lactis subsp. lactis immobilization and lactic acid and hydrogen peroxide (H2O2) production by stains immobilization in batch fermentation process was investigated using a bioreactor with recycling. Lactic acid fermentation using syrup of molasses treated and diluted at 50% (MSTD 50%) was not supplemented by ingredients concentrations. Cells immobilization showed higher sugar utilization, higher H2O2accumulation and higher lactic acid production than did free cells. Improvement incompounds production was noticed with immobilization of Lactococcus lactisisolated from the molasses (Lc.lML) compared with strains isolated from the cow's milk (Lc.lCM). In pure culture, the kinetic of the production of lactic acid and H2O2 by the two strains in MSTD 50% was compared with than did in Elliker broth. Key words: Lactococcus lactis, lactic acid, hydrogen peroxide, immobilization, molasses, pouzzolane