Alternative media for lactic acid production by Lactobacillus delbrueckii NRRL b-445

Abstract

Lactic acid bacteria are generally recognized as nutritionally fastidious. The complexity of the media increases the cost of lactic acid production. In this study a low-cost nutrient medium based on corn steep liquor (CSL) was developed for lactic acid production by Lactobacillus delbrueckii NRRL B-445. Starting from a medium containing 90 g l(-1) glucose and 20 g l(-1) CSL as a sole nutrient source, 70.7 g l(-1) lactic acid was obtained with an economic efficiency of 98 g lactic acid per E nutrient. Other media, made with CSL and each individual component (yeast extract, peptone, sodium acetate, sodium citrate, K2HPO4, MgSO4.7H(2)O, MnSO4.H2O or FeSO4.7H(2)O) of a general (Mercier) lactobacilli medium were also assayed. The highest economical efficiency (134 g lactic acid per E nutrient) was obtained supplementing 10 g l(-1) CSL with 0.05 g l(-1) FeSO4.7H(2)O. Additionally, lactic acid production and glucose consumption were mathematically modelled and the regression parameters obtained were correlated with CSL concentration by linear or exponential equations.