Peer review

γ-Aminobutyric acid (GABA), a natural “neuro-vitamin”, exerts an irreplaceable role in modulating gut microbiota, thereby influencing brain function and host behavior. However, there are ethical and safety challenges based on clinical trials and model animals. Herein, an <i>in vitro</i> fecal slurry fermentation model was constructed to explore the impacts of GABA and its precursor monosodium glutamate (MSG) on the regulation of human intestinal microorganisms. Both GABA (25.43%-41.57%) and MSG (28.72%-49.59%) supplementation promoted the relative abundance of Actinobacteria phylum compared to the Ctrl group (18.68%), particularly characterized by <i>Bifidobacterium</i> representation in fecal. Notably, high levels of GABA and MSG addition significantly reduced the abundance of Bacteriodota by 65.15% and 77.61%. respectively. Analysis of short-chain fatty acids (SCFAs) suggested that high levels of GABA supplementation significantly increased the production of total acid and acetic acid through fermentation. Moreover, the Spearman correlation analysis of high GABA treatment group showed a significant positive association between acetic acid, isobutyric acid and 2-methylbutyric acid with the genera <i>Bifidobacterium</i>, <i>Subdoligranulum</i> and <i>Lachnoclostridium</i> after fecal fermentation, respectively. The <i>in vitro</i> colonic fermentation model established in our study may offer valuable views for future studies on the GABA-gut microbiota interaction under the background of nutritional intervention treatment.