Integrated bioprocess optimization of cellulase and xylanase production by Penicillium argillaceum using lignocellulosic agro-industrial residues.

The efficient production of lignocellulolytic enzymes from low-cost agro-industrial residues is essential for sustainable biomass valorization. However, Penicillium argillaceum remains largely underexplored as a potential producer of cellulase and xylanase and studies on their simultaneous optimization are scarce. In the present study, an integrated bioprocess optimization strategy was developed for enhanced cellulase and xylanase production by Penicillium argillaceum NCIM 1148 using lignocellulosic agro-industrial substrates under submerged fermentation. Initial substrate characterization and screening identified wheat bran as the most effective carbon source and peptone as the most suitable nitrogen source for enzyme induction. One-factor-at-a-time (OFAT) experiments established pH 5.5 and 35 °C as favorable cultivation conditions. Subsequently, Plackett-Burman Design (PBD) was employed to screen significant process variables, identifying wheat bran and peptone as the major contributors to enzyme production. These variables were further optimized using Response Surface Methodology (RSM) based on a Central Composite Design (CCD). Experimental validation under optimized conditions yielded cellulase and xylanase specific activities of 2.65 U/mg and 3.70 U/mg, respectively. Compared with the best condition obtained during the screening stage, optimization resulted in a 1.16-fold increase in cellulase activity and a 2.58-fold increase in xylanase activity. The developed RSM models demonstrated satisfactory predictive performance, with prediction errors below 13%. Fourier-transform infrared (FTIR) analysis further revealed structural modifications in wheat bran after fungal treatment, evidenced by reductions in lignin- and hemicellulose-associated functional groups. Overall, this study demonstrates the potential of P. argillaceum NCIM 1148 as an efficient producer of lignocellulolytic enzymes and highlights the effectiveness of a sequential OFAT-PBD-RSM strategy for cost-effective enzyme production and lignocellulosic biomass valorization.