Valorization of lignocellulosic waste biomass derived from wine industry to produce lactic acid and nutraceuticals

The present research focuses on the valorization of lignocellulosic waste biomass derived from the wine industry, particularly grape stalks, for the production of lactic acid and nutraceutical compounds. The study addresses the need for sustainable approaches to biomass valorization within a circular economy framework, applying advanced biorefining strategies to extract polyphenols, pectin and cellulose from grape stalks. A cascade process was developed, integrating microwave-assisted subcritical water treatment for polyphenol extraction, followed by microwave-assisted alkaline delignification for cellulose enrichment. The resulting cellulose was successfully fermented into lactic acid using Clostridium thermocellum strains. Clostridia, and in particular C. thermocellum, represent key microbial candidates for second-generation biorefineries due to their metabolic versatility, their ability to directly utilize lignocellulosic feedstocks, and their compatibility with consolidated bioprocessing (CBP) strategies. To further enhance process efficiency, metabolic engineering approaches were applied to improve lactic acid production. This highlights the complementary importance of both effective pretreatment, to make cellulose more bioavailable, and microbial optimization, to enhance strain performance in bioprocesses. Additionally, to recycle the other biomass components, polyphenol extracts were characterized for their antioxidant and antimicrobial properties, while pectin fractions were evaluated for prebiotic potential. This integrated approach enhances the environmental and economic sustainability of wine industry waste management by transforming underutilized biomass into valueadded bioproducts for diverse industrial applications, including food, pharmaceuticals, and bio-based materials