Advancements in lignocellulosic biorefining: An integrated approach for achieving complete conversion of unsterilized peanut shells into high-titer ethanol and succinic acid.

The inefficient utilization of carbon sources poses a critical bottleneck in lignocellulose biorefinery processes. This study aimed to devise an integrated approach for efficiently releasing the fermentable sugars from pretreated peanut shells, and subsequently converting the hexoses and pentoses into ethanol and succinic acid (SA), while minimizing carbon dioxide emissions. An enhanced cellulolytic enzyme catalytic system (CECS) has been developed through the optimization of accessory enzymes and additives. This system synergistically boosted both the thermal stability and catalytic activity of the cellulase, and enhanced the glucose yield by 15.95 % at a substrate loading of 10 % (w/v). The implementation of a fed-batch strategy improved the efficiency of high-solids (25 % w/v) enzymatic hydrolysis, when it was integrated with the developed CECS, a remarkable glucose yield of up to 79.40 % was achieved. The semi-simultaneous saccharification, in conjunction with a step-wise fermentation process, enabled the efficient conversion of pentoses and hexoses from pretreated peanut shells into high titers of ethanol (83.13 g/L) and SA (45.21 g/L) under non-sterilized conditions. This approach achieved conversion rates of up to 41.10 g ethanol and 100.57 g SA per kilogram of peanut shells raw material, while effectively mitigating carbon dioxide emissions during the process.