Genomic comparison of GABA-producing Levilactobacillus brevis and Companilactobacillus zhachilii strains from Thai fermented foods

Two lactic acid bacteria strains, ASK-1 and ANB-1, capable of producing GABA, were isolated from traditional Thai fermented pork sausage ( sai-krog-prieo ) and fermented pork ( nham ), respectively. Strains ASK-1 and ANB-1 produced 9.12 ± 0.51 g/L and 12.73 ± 0.57 g/L of GABA, respectively, from 30 g/L of monosodium glutamate after 72 hours of cultivation at 30°C. Genome analysis revealed that strain ASK-1 (genome size: 2,343,673 bp) was identified as Levilactobacillus brevis ATCC 367, with an average nucleotide identity by BLAST (ANIb) value of 98.86%. Strain ANB-1 (genome size: 2,748,085 bp) had an ANIb value of 96.92% with Companilactobacillus zhachilii HBUAS52074 ^T . Further genomic studies of strains ASK-1, ANB-1, and HBUAS52074 ^T identified the presence of GABA-producing genes ( gadA and gadB ) using the KofamKOALA-KEGG Orthology database. Phenotypic characterization and 16S rRNA gene sequencing further supported these findings. Strain ASK-1 (1,566 bp) exhibited 100% 16S rRNA gene sequence similarity to L. brevis ATCC 14687 ^T , confirming its identification as L. brevis . Similarly, strain ANB-1 (1,567 bp) showed 99.93% similarity to HBUAS52074 ^T , confirming its identification as C. zhachilii . These strains demonstrated efficiency and safety in GABA production, making them promising candidates for further studies to optimize GABA yield and assess their probiotic properties. They hold significant potential for the development of functional foods and the enhancement of food fermentation processes in both local and industrial contexts.