Co-Cultivation of Penicillium sp. AKB-24 and Aspergillus nidulans AKB-25 as a Cost-Effective Method to Produce Cellulases for the Hydrolysis of Pearl Millet Stover

Hydrolysis of cellulose and hemicelluloses into fermentable sugars is the primary step for the production of fuels and chemicals from lignocellulosic biomass, and is often hindered by the high cost of cellulolytic and hemicellulolytic enzymes. In the present study coand monocultures of Penicillium sp. AKB-24 and Aspergillus nidulans AKB-25 were used under a variety of fermentation conditions to optimize enzyme production. Wheat bran was found to be the optimal carbon source yielding maximum enzyme production under solid-state fermentation conditions due to its higher water retention value (175%) and minimum C/N ratio (22.7). Penicillium sp. AKB-24 produced maximum endoglucanase (134 IU/gds), FPase (3 FPU/gds), β-glucosidase (6 IU/gds) and xylanase (3592 IU/gds) activities when incubated for 7 days at 30 ̋C and pH 7 with a moisture content of 77.5%, and 1.2% yeast extract and 0.1 (w/v) sodium dodecyl sulphate supplement. Co-culturing of Penicillium sp. AKB-24 and Aspergillus nidulans AKB-25 enhanced endoglucanase, FPase, and exoglucanase activities by 34%, 18%, and 11% respectively compared to Aspergillus nidulans AKB-25 alone under optimum conditions. Enzymes produced by co-cultivation released equal amounts of reducing sugars at an enzyme dose of 15 FPU/g and reaction time 72 h, but the required quantity of enzyme was 14% less compared to enzyme released from Aspergillus nidulans AKB-25 mono-culture. In conclusion, co-cultivation of Penicillium sp. AKB-24 and Aspergillus nidulans AKB-25 to produce enzymes for the hydrolysis of pearl millet stover is more cost-effective than cultivation with Aspergillus nidulans AKB-25 alone.