Co-production of gamma amino butyric acid (GABA) and lactic acid using Lactobacillus plantarum LP-9 from agro-residues

Abstract

Microbial conversion of agro-residues into valuable products such as GABA and lactic acid is of considerable environmental and biotechnological significance. In this study, twenty-nine lactic acid bacteria were isolated from traditional fermented milk and screened for lactic acid and GABA production. Among these, one strain LP-9, identified as Lactobacillus plantarum demonstrated co-production of GABA (0.86 g/L) and lactic acid (19.81 g/L) in De Man, Rogosa and Sharpe (MRS) broth supplemented with 1% monosodium glutamate (MSG). Under RSM optimized conditions, cumulative effect of factors influencing microbial product formation led to a two-fold increase in production of GABA (1.53 g/L) as compared to unoptimized conditions along with substantial production of lactic acid (21.87 g/L). Further, to develop an economical bioprocess on these lines, L. plantarum LP-9 was tested for its capability to utilize agro residues (wheat bran, rice bran and corn bran) and cassava (starchy food crop as control) in form of carbon source for GABA and lactic acid production using conditions optimized in RSM. The substrates were saccharified with enzyme cocktail containing α-amylase, amyloglucosidase, and cellulase followed by fermentation with L. plantarum LP-9 in MRS medium supplemented with 1% MSG but without sugar. The results showed that the saccharified agroresidues tested gave significant and comparable production of GABA (1.14–1.30 g/L) and lactic acid (22.83–29.82 g/L) as that obtained with cassava (1.39 g/L GABA and 31.76 g/L LA). This study illustrated the potential of isolate L. plantarum LP-9 to co-produce GABA and lactic acid from agro residues via biorefinery approach. The developed bioprocess will also help in safe, efficient and ecofriendly disposal of agriwastes.