Improvement of GABA production and survival of Lactobacillus brevis G42 in simulated gastrointestinal conditions by soy- alginate microcapsulation

Gamma-aminobutyric acid (GABA) is a non-protein amino acid existing in bacteria, plants, and vertebrates. GABA is especially well-known because of its physiological role in the neurotransmission, induction of hypotension, diuresis, and tranquility. GABA is biologically synthesized by GABA-producing lactic acid bacteria (GLAB) which are widely used as starters in the fermented foods. In this study, GABA-producing strain were chosen to be microencapsulated by soy protein isolate (SPI)-alginate using emulsion method. Encapsulation efficiency and entrapment of GLAB into soy protein-alginate microcapsules (SAE) was confirmed by scanning electron microscope. The GABA-producing ability and survivability of the microencapsulated GLABs were investigated in the human gastro-intestinal simulant. For screening of GLAB strains, the isolates from Tarkhineh and fermented carrot were separately cultivated in MRS broth supplemented with 1% (w/v) monosodium glutamate (MSG). The GABA production efficiency was studied by thin layer chromatography (TLC) and High performance liquid chromatography (HPLC). According to the recorded chromatograms, Lactobacillus brevis PML1 isolated from Tarkhineh and Lactobacillus brevis G42 from fermented carrot showed GABA producing ability of 304 mg/L and 2511 mg/L, after 30 h at 30 °C, respectively. The results indicated that survival and GABA production improved upon microencapsulating the bacteria due to the good cell protection provided by soy protein isolate-alginate coating. In long with previous reports, this study proves the potential of microencapsulation toward increased efficiency of GABA production in functional foods.