Optimization of bioprocess steps through response surface methodology for the production of immobilized lipase using Chaetomium globosum via solid-state fermentation

The present study demonstrates the maximum production of lipase via solid-state fermentation (SSF) by a novel strain of Chaetomium globosum , through lignocellulosic biomass valorization. After lignocellulosic biomass screening, Vachellia nilotica (babul) yielded the maximum lipase (53.1 ± 0.2 U/mL) activity after 72 h. Different bioprocess parameters, including pH, temperature, moisture content, inoculum size, and time periods, were optimized by the central composite design of response surface methodology (RSM). The maximum lipase yield (52.48 ± 5.3 U/mL) was achieved at pH 9.0, moisture 70%, incubation time 24 h, inoculum mass 1 mL, and temperature 30 °C. F-value 26.21 and p -value 0.00 by the analysis of variance indicate the significance of the proposed model. The coefficient of determination (R 2 ) 95.60% was used to check the goodness of fit of the model, having a value of which indicates the model accuracy. Lipase was precipitated and purified with 80% ammonium sulfate followed by Sephadex G-100 column with 305.8 U/mg specific activity. The molecular weight of purified lipase was 60 kDa, estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The optimally purified lipase was immobilized on chitosan (natural biopolymer) using different lipase concentrations (0.5, 1, and 2 mL) to check the beads constancy. It was observed that lipase (0.5 mL) adsorbed on chitosan result in the highest activity compared to the free lipase. Chitosan-immobilized lipase showed high thermal stability at 40 °C for 5 h. It also exhibited stability for up to 7 reuse cycles. Furthermore, lipase showed its good effect in the detergent industry by demonstrating compatibility with the Sufi detergent brand. In conclusion, the recently produced lipase from the lignocellulosic biomass has a great potential to be used as an additive in the detergent industry.