Assessment of GABA enrichment and probiotic potential in fermented okpeye by Bacillus amyloliquefaciens AUK.

Gamma-aminobutyric acid (GABA) is a non-protein amino acid synthesized from glutamate by the enzyme glutamate decarboxylase (GAD) and plays an essential role in the nervous system. This study investigated the production and optimization of GABA by Bacillus amyloliquefaciens AUK, isolated from okpeye seasoning, and assessed its probiotic potential. Okpeye samples were collected from markets in Nsukka L.G.A., Enugu State, Nigeria. Using response surface methodology (RSM), the study optimized GABA production from the microbe under specific conditions: 2% (w/w) monosodium glutamate, 71 h fermentation, 39.4 °C temperature, and 5% (w/v) inoculum concentration. While unoptimized okpeye fermentation yielded 43.30 mg/100 g GABA, optimized conditions increased production of GABA to 246.54 mg/100 g, a 5.56-fold improvement. The isolate demonstrated probiotic properties by surviving acidic and bile conditions, showing moderate hydrophobicity, and exhibiting antimicrobial activity against pathogens. These findings highlight the potential of B. amyloliquefaciens AUK to boost the functional properties of okpeye seasoning. This suggests its application as a starter culture for producing GABA-enriched functional foods, contributing to the development of probiotic-rich products with enhanced health benefits. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-025-06223-0.