Bioprocess optimization of Penicillium oxalicum SM03 for the production of cellulases on freshwater alga Salvinia molesta biomass in solid-state fermentation

The freshwater weed Salvinia molesta was used as a substrate for the production of cellulase in solid-state fermentation. The lignocellulose material was used as the sole source of carbon and energy. The decaying Salvinia molesta plant was used as the source of cellulase-producing fungi, and 12 strains were isolated. The strain SM03 exhibited maximum cellulase (9.1 ± 0.1 U/mL carboxymethyl cellulase, 10.4 ± 0.08 U/mL β-glucanase, and 0.72 ± 0.09 U/mL filter paperase) production. The strain SM03 was characterized as Penicillium oxalicum SM03 based on 18S rDNA gene sequencing. Solid-state fermentation was performed using P. oxalicum SM03, and culture conditions were optimized for maximum cellulase production. The present findings revealed that maximum cellulase production was achieved at 1% ammonium sulphate, 30 °C incubation temperature, and after 96-h incubation. A central composite design experiment was performed to determine the optimum pH level, fermentation period, and ammonium sulphate concentration. Response surface methodology improved twofold production of carboxymethyl cellulase (p = 0.0033), 1.9-fold increased enzyme yield in β-glucanase (p = 0.0004), and 2.1-fold increased filter paperase activity (p = 0.0004). The saccharification efficacy of cellulase on chemically pretreated S. molesta biomass was tested. The fungal cellulases improved, reducing sugar yield from 0.187 ± 0.02 to 0.417 ± 0.03 g/g.