Valorisation of grape stalks and pomace for the production of bio-based succinic acid by Actinobacillus succinogenes

Abstract

Valorisation of food supply chain waste for the production of bio-based platform chemicals will facilitate the transition to the sustainable bio-economy era. To this end, a novel process has been developed for the conversion of grape pomace and stalks into bio-based succinic acid. Free sugars (2.55 g/100 g), a phenolic-rich extract (185.75 mg gallic acid equivalent per g extract with Antioxidant Activity Index of 1.03) and lipids (8.2 g/ 100 g) were initially extracted from grape pomace. Residual grape pomace solids were subsequently mixed with grape stalks (1:1 ratio) and treated with sodium hydroxide (1%, w/v) for lignin removal. The residual solids were treated with varying H2SO4 concentrations (3–10 %, v/v) followed by enzymatic hydrolysis using different dosages of cellulases and β-glucosidase leading to the release of 22.7 g glucose per 100 g remaining solids (48 % cellulose hydrolysis). Actinobacillus succinogenes fed-batch cultures carried out with the crude hydrolysate as fermentation medium and free sugars from grape pomace as feeding solution resulted in 40.2 g/L succinic acid concentration with a yield of 0.67 g/g and productivity of 0.79 g/L/h. This study proposes for the first time a sustainable process for valorising grape pomace and stalks for efficient bio-based succinic acid production integrated with the extraction of value-added fractions.