Produção de celulases a partir de resíduo da casca de acerola visando à produção de etanol celulósico

Abstract

Brazil is one of the world's largest producers of agricultural waste, acerola residue being one. This residue, primarily composed of polysaccharides (cellulose and hemicellulose) and aromatic macromolecules (lignin), serves as a valuable raw material for cellulase and hemicellulase-producing microorganisms, thus an excellent substrate for second-generation ethanol production. This study assessed the potential of acerola waste, pre-treated with 1% sulfuric acid, in producing cellulolytic enzymes via solid-state fermentation using Trichoderma reesei, and the use of the enzymatic extract in 2G ethanol production through a consolidated bioprocess. The residue underwent physicochemical characterization before and after pre-treatment, measuring moisture, extractables, total ash, and levels of cellulose, hemicellulose, and lignin. The enzymatic extract was characterized for optimal temperature, best extraction buffer and thermal stability. Enzymatic activity was determined using filter paper (FPase) and Carboxymethyl cellulose (CMCase) substrates. Acid pre-treatment led to over 90% reduction in hemicellulose and nearly 15% reduction in lignin content. Activities found were 3.84 UCMC/g for CMCase and 3.29 UFP/g for FPase after 24-hour cultivation in optimized conditions using sodium citrate buffer. Though lignocellulosic ethanol production was inhibited, 8.26g/L glucose was detected at the process's end. The findings indicate that acerola waste is a viable substrate for obtaining cellulases and fermentable sugars, contributing to the exploration of alternative uses for acerola residues.