Abstract:

The objectives of this work were to optimize the medium composition for improved production ofγ-aminobutyric acid (GABA) by the fermentation of Lactobacillus brevis BS2 with Zinc-enriching ability and to clone and sequence the glutamate decarboxylase (GAD) gene of this strain. GABA quantification was performed using pre-staining paper chromatography method. The optimal medium composition was determined as follows: carbon source, glucose; nitrogen source, soybean peptone plus beef extract; carbon/nitrogen ratio, 1:1; and substrate concentration, 1%, and the maximum GABA production reached up to 6.32 g/L under such conditions. CTAB method was used for the extraction of genomic DNA from stain BS2, and the extracted genomic DNA was used as the template for the amplification of a 1407 bp gad gene by touch down PCR. The gad gene was finally cloned into the T vector. The sequencing analysis showed that the gene had 98% homology with that of Lactobacillus brevis BH2, suggesting that the obtained target gene is the gad gene of Lactobacillus brevis.

Key words: Gamma-aminobutyric acid, Lactobacillus brevis BS2, glutamate decarboxylase, medium optimization, sequence analysis