OPTIMIZATION AND CHARACTERIZATION OF GABA PRODUCTION BY LACTIPLANTIBACILLUS PLANTARUM PPKMB1 AND PRELIMINARY CYTOTOXICITY AGAINST HCT-116 COLORECTAL CANCER CELLS

Abstract

γ-Aminobutyric acid (GABA) is a bioactive non-protein amino acid, and Lactic Acid Bacteria (LAB) offer a food grade route to its production. A GABA-producing isolate from raw cow milk was identified as Lactiplantibacillus plantarum PPKMB1 (GenBank MZ951173) by phenotypic and 16S rRNA analyses. It survived pH 3.0 (>90%, 3 h), tolerated >0.8% ox bile and 4–8% NaCl, showed 35% hydrophobicity and was γ-haemolytic. GABA production was peaked at 48 h, initial pH 7.0 and 40 °C, with xylose (464.2 µg/mL) and tryptone (610.8 µg/mL) as the best carbon and nitrogen sources. TLC (Rf 0.672), UV–visible and FTIR spectroscopy and GC-MS (retention time 2.963 versus 2.912 min for the standard) supported GABA identity, and GC-MS quantified 862.39 mg/L in the purified sample. An L1-derived fraction (6.25–100 µg/mL, 24 h) reduced HCT-116 colorectal cancer cell viability from 97.4% to 31.4% (MTT assay), with a preliminary IC₅₀ of approximately 76 µg/mL; doxorubicin (5 µM) gave 32.3%. Because the fraction was not pure GABA, the cytotoxicity cannot be attributed to GABA alone, and mechanistic and normal-cell studies are required.