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 Pl -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 € nutrient. Other media, made with CSL and each individual component (yeast extract, peptone, sodium acetate, sodium citrate, K 2 HP0 4 , MgSO 4 -7H 2 O, MnS0 4 -H 2 0 or FeSO 4 -7H 2 O) of a general (Merrier) lactobacilli medium were also assayed. The highest economical efficiency (134g lactic acid per € nutrient) was obtained supplementing 10 gl -1 CSL with 0.05 gl -1 FeSO 4 -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.