Waste-to-resource: Enhanced production of cellulases and lichenase from lignocellulosic biomass via mutated Bacillus subtilis

Abstract

Microbial enzymes such as cellulases and lichenase hold great importance in industrial and biotechnological sectors. This study demonstrates the successful enhancement of cellulase and lichenase production in Bacillus subtilis through strain improvement and process optimization. By using ethyl methanesulfonate (EMS) for bacterial mutagenesis followed by comprehensive screening, a mutant strain was obtained that exhibited superior enzymatic performance compared to the wild-type strain. Subsequent optimization studies utilizing low-cost lignocellulosic substrates revealed wheat straw and barley flour as the most effective agricultural wastes for cellulase and Lichenase production under ideal fermentation conditions (pH 7.0, 35 °C, 72 h incubation). For both enzymes, optimal production was reached when cultivated with sucrose and tryptone as the primary carbon and nitrogen source. Detailed kinetic characterization of the enzymes produced by the mutant strain showed that there is an increase in enzyme substrate binding affinity as well as rate of catalysis in endoglucanase, exoglucanase, β-glucosidase, and lichenase. The mutant enzymes exhibited remarkable thermostability and pH stability, retaining nearly 80 % of their initial activity over a 4-h period. These findings provide both fundamental insights into the enhancement of enzymes through chemical mutagenesis and practical solutions for industrial enzyme production. The demonstrated approach combines strain improvement with sustainable utilization, offering a viable pathway to reduce production cost and maintain high yields. This work particularly highlights the potential of agricultural residues in biotechnological applications and establishes a framework for future strain development efforts targeting hydrolytic enzyme production.