Genomic insights into high GABA production by Levilactobacillus brevis Q3-11 and its application in developing functional kiwifruit juice.

This study aimed to develop a functional fermented kiwifruit juice by utilizing a novel, high-yield γ-aminobutyric acid (GABA)-producing lactic acid bacterium. A strain identified as Levilactobacillus brevis Q3-11 was isolated from naturally fermented kiwifruit juice. Its genomic basis for GABA production was elucidated through whole genome sequencing, which confirmed the presence of the glutamate decarboxylase system (GADB and GADC genes) and a potential putrescine degradation pathway. Subsequent analysis demonstrated the strain's probiotic properties and fermentation suitability. When applied to kiwifruit juice fermentation, Lev. brevis Q3-11 exhibited outstanding performance. The GABA concentration reached 3.67 g/L (a 4.17-fold increase), the highest level reported to date in a fruit juice matrix without precursor addition. Moreover, the fermentation significantly preserved bioactive compounds, including vitamin C, total phenols, and flavonoids, leading to enhanced antioxidant capacity. The sensory profile was also improved, evidenced by a significant increase in organic acids and volatile flavor substances. In conclusion, Lev. brevis Q3-11 is a promising probiotic starter culture for the development of functional fermented juices with high GABA content, enhanced nutritional value, and a superior flavor profile.