Optimisation of the hydrolysis and yeast fermentation of Jerusalem artichoke tubers for fermentable sugar release and product characterisation

Jerusalem artichoke tubers are an underutilised inulin-rich crop with potential as a sustainable substrate for a subsequent food-grade fermentation. This study evaluated thermo-acid pretreatments, including mineral acid and food-grade vinegars, combined with hydrothermal, pressurised heating, and microwave processing to enhance fermentable sugar release. Acid-assisted processing increased soluble sugars (8.6–15%); while vinegar pretreatment generated hydrolysates at fermentation-compatible pH (~5), eliminating post-hydrolysis neutralisation. All hydrolysates supported growth of Generally recommended as safe (GRAS) yeast Saccharomyces cerevisiae, Candida utilis, and Yarrowia lipolytica. Analysis confirmed inulin depolymerisation and enrichment of amide I–II bands in fermented biomass and fermentation-associated metabolites, including carbohydrate depletion, and presence of polyunsaturated fatty acids and phenolic-associated compounds. Elemental analysis of the yeast post-fermentation revealed a strain-dependent mineral enrichment which correlated with hydrolysate composition. These findings support vinegar-assisted processing as a food-grade route to fermentation-ready Jerusalem artichoke hydrolysates.