Bioethanol production via enzymatic saccharification and fermentation of food industry by-products

Introduction

The valorization of food industry by-products as feedstocks for biofuels is central to the concept of circular bioeconomy. The enzymatic conversion of residual biomass into fermentable sugars is a cornerstone of sustainable biorefinery strategies. However, bioconversion of lignocellulosic biomass remains challenging due to its recalcitrant structure. Combining pretreatment technologies with optimized enzymatic cocktails offers significant potential for the enhanced conversion of residual biomass to bioethanol.

Methodology

Wheat straw and potato peels were used as feedstocks. Wheat straw was subjected to hydrothermal pretreatment in the presence of ethanol at different temperatures, and the hydrolytic potential of a commercial cellulolytic cocktail was subsequently evaluated. The performance of the cocktail was optimized through supplementation with hemicellulases and auxiliary enzymes. Potato peels were vacuum-dried and further hydrolyzed into glucose by commercial α-amylases and glucosidases. In both cases, substrate and enzyme loadings were optimized and the saccharification process was scaled up. Finally, fermentation was performed using Ethanol Red yeast for bioethanol production.

Results

Hydrothermal pretreatment of wheat straw under different conditions resulted in reduced hemicellulose and lignin content. Subsequent saccharification achieved a 30 % w/w conversion of cellulose into glucose, while for potato peels a 45 % w/w conversion into glucose was achieved. Wheat straw hydrolysis was further enhanced through supplementation with non-specific endoxylanases and arabinofuranosidases. The resulting hydrolysates were successfully used as substrates for yeast fermentation into bioethanol.

Conclusions

Food industry by-products can serve as efficient feedstock for bioethanol production. Enhancement of commercial cellulolytic cocktails by hemicellulases and auxiliary enzymes can significantly improve biomass saccharification, thereby advancing the efficiency of industrial bioprocesses for bioethanol production.