Comparative evaluation of chemical and UV mutagenesis with post-mutagenesis process optimization for enhanced cellulolytic enzyme production by Aspergillus oryzae NCIM 637

Abstract

This study evaluated the effects of chemical and UV mutagenesis on Aspergillus oryzae NCIM 637 to enhance cellulolytic enzyme production under solid-state fermentation (SSF) using groundnut shells. Chemical mutagenesis has produced the most consistent improvements. The chemically treated vegetative cell mutant M4 showed a 58.7 % increase in metabolic activity and substantial gains in enzyme yields: endoglucanase (222.5 IU/gDW, 77.9 %), exoglucanase (238 IU/gDW, 62.5 %), β-glucosidase (560.7 IU/gDW, 61.9 %), β-xylanase (652.8 IU/gDW, 55.4 %), β-amylase (221.4 IU/gDW, 48.7 %), and proteinase (196.6 IU/gDW, 2.1-fold over WT). UV mutagenesis has been shown to elicit more selective responses than chemical mutagenesis. The vegetative cell mutant M1 showed the highest improvement, with an 85.3 % increase in metabolic activity, alongside elevated β-xylanase and proteinase activities. Statistical analysis confirmed the significant effects of mutagen type and incubation time (p < 0.001). RSM modeling provided strong predictive fits (R² = 0.93–0.97) with desirability indices of >0.95. Process optimization further increased the yields, particularly for β-xylanase (70.1 %) and endoglucanase (61.96 %). Overall, chemical mutagenesis generated broad-spectrum and stable improvements, whereas UV irradiation selectively stimulated specific enzymatic pathways. These results demonstrate a scalable approach for valorizing agro-residues through optimized fungal mutagenesis and SSF, advancing sustainable enzyme production for industrial applications.