Effects of controlled fermentation by Lactiplantibacillus plantarum PBS067 on Vitis vinifera L. leaf extract

Vitis vinifera L. leaves represent one of the most phenolic-rich grapevine biomasses, exhibiting a broad spectrum of biological activities, including prebiotic and microbiota-modulating ones. However, as they are mainly regarded as agro-industrial waste, they are still an underexploited resource. Probiotic-driven fermentation may offer a promising strategy to enhance their bioactive potential while addressing this challenge. The aim of this study was to evaluate the effects of the in vitro fermentation of Vitis vinifera L. leaf extract (VVLE) by Lactiplantibacillus plantarum PBS067 in terms of phenolic content, antioxidant activity, lactic acid and protein content, and metabolomic profile. Our analysis shows the prebiotic activity of VVLE, as VVLE-supplemented medium allowed probiotic growth without toxic effects. Leaves fermentation led to a significant enrichment in lactic acid and the biotransformation of complex plant-secondary metabolites into smaller derivatives. However, VVLE antioxidant capacity slightly decreased after the fermentation, likely due to the phenolic conversion itself. These results highlight how controlled lacto-fermentation valorizes grapevine leaves, transforming them into sustainable upcycled bioactive products with potential applications within cosmetics, pharmaceuticals, nutraceuticals and complementary medical product sectors.