A novel "laccase-degradation and GABA-compensation" strategy mediated by Lactococcus lactis subsp. lactis GLM-1 for the safe and targeted detoxification of ginkgo seeds.

Ginkgo biloba L. seeds are valued for their bioactive compounds but contain the neurotoxin 4'-O-methylpyridoxine (MPN), limiting their safe use. This study developed a novel "laccase-degradation and GABA-compensation" strategy using a food-grade bacterium, Lactococcus lactis subsp. lactis GLM-1, to achieve detoxification with bioactive preservation. The study initially confirmed that while free laccase effectively degrades MPN, it nonspecifically oxidizes total flavonoids and terpene lactones. Furthermore, using a model Caenorhabditis elegans, it was elucidated that MPN impedes GABA production by interfering with pyridoxal phosphate synthesis, thereby inducing neuronal hyperexcitability, and it was demonstrated that exogenous GABA effectively alleviates this neurotoxicity. Subsequently, from 125 lactic acid bacteria strains possessing putative laccase genes and GABA-producing capacity, GLM-1 was selected for its superior dual functionality. Whole-genome analysis and molecular docking revealed that GLM-1 possesses a complete GABA synthesis and secretory pathway, lacks GABA transaminase genes, and its laccase exhibits potential for stable binding with MPN. In a ginkgo seed semi-solid fermentation system, GLM-1 reduced MPN content by 73.0%, increased GABA content by 30.68%, and effectively preserved total flavonoids and terpene lactones. Further optimization of the fermentation process enhanced the GABA yield to 3.98 mg g-1 (a 58.6% increase) and improved the MPN degradation rate to 76.0%, while key bioactive components were still well maintained. This study systematically establishes an integrated technical framework for the bio-detoxification of ginkgo seeds, encompassing theoretical conception, functional strain screening, mechanistic elucidation, and process optimization, thereby providing a novel approach and microbial resource for the high-value exploitation of medicinal and edible plants.