Application of Cellulase From Mutated Aspergillus sp. for the Production of Sustainable 2G Ethanol From Sugarcane Bagasse

Abstract

Sugarcane bagasse (SB) is a lucrative feedstock for sustainable fuel production, but economical conversion into fermentable sugars and ethanol presents challenges from a biorefinery perspective. The present study aimed to screen and identify a robust cellulase-producing fungal strain to improve the saccharification of SB. Aspergillus fumigatus exhibited enhanced cellulase activity when untreated SB served as the substrate. The EMS mediated chemical mutagenesis of A. fumigatus with 200 mM EMS further enhanced the cellulase production by approximately 23.47%, relative to the wild-type strain. The process optimization method demonstrated peak cellulase activity on the 6th day of incubation, at 33 °C, and with an inoculum size of 5 × 10⁷ spores. The optimization of the filter paper assay enhanced the maximum activity to 2.5 U/mL by maintaining 6 pH and 55 °C, along with the subsequent addition of MnCl₂ ions to the reaction mixture. The Taguchi orthogonal array was employed to optimize the process parameters of enzymatic hydrolysis of alkali-pretreated SB, demonstrating highest efficiency when hydrolysis parameters were set to pH 4, 55 °C, 10 U enzyme, and 20 g/L substrate (SB) loading. The hydrolysate was utilized to evaluate bioethanol production employing Saccharomyces cerevisiae MTCC 824. The strain generated 4.2 g/L of ethanol with a total yield of 0.21 g/g. This study seeks to manage agricultural residues and wastes, generating a nutrient-rich hydrolysate that can be utilized by yeast strains for bioethanol production, thus rendering the entire process sustainable, environmentally friendly, and cost-effective.