Lactic acid production by Lactobacillus paracasei 168 in discontinuous fermentation using lucerne green juice as nutrient substitute

Abstract

The aim of this study was the utilization of lucerne green juice (LGJ), obtained in 2005 and 2008, as nutrient substitute in lactic acid fermentation using Lactobacillus paracasei 168, in a discontinuous fermentation process with the addition of 55g/L glucose and 15g/L yeast extract. The LGJ after pressing fresh green mass contains a series of nitrogen-containing compounds and inorganic salts that are essential for cell growth. The strain used, L. paracasei 168, achieved at 40.5°C and pH 6.0 a maximum productivity of up to 2.56gL-1 h-1 and a lactic concentration close to 45.97g/L in trial A (LGJ 2008/glucose), 2.19gL-1 h-1, 47.23g/L in trial B (LGJ 2005/glucose), 2.93g-1 h-1, 42.27g/L in trial C (LGJ 2008/glucose/yeast extract), and 2.68g-1 h-1, 47.33g/L in trial D (LGJ 2005/glucose/yeast extract). Addition of yeast extract in trials C and D induced faster growth of L. paracasei 168. Lactate yields of about 87% were obtained in all trials. The lactic acid formed was the optically pure L-(+)-isomer at up to 97% in trial B. Pearson's analysis showed that the level of lactic acid in the control trial was positively and significantly correlated with trial A (r2 = 0.9899), B (r2 = 0.9582), C (r2 = 0.9901), and D (r2 = 0.9938), with p<0.0001. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.