Biomass utilization for production of cellulolytic enzymes from a novel Penicillium citrinium LHB3 and the physicochemical properties of the enzyme

Efficient conversion of lignocellulosic biomass into fermentable sugars is critical for sustainable bioenergy production. This study reports the production and comprehensive characterization of a robust cellulase system from Penicillium citrinium LHB3 using agro-wastes under solid-state fermentation. Maximum enzyme production was achieved at 30–50 °C, pH 3–8, and 60–80% moisture, with cassava peel supporting the highest yield. The cellulase components (FPase, endoglucanase, and β-glucosidase) exhibited optimal activities between 40–60 °C, with distinct pH optima of 10, 11, and 3, respectively. Notably, FPase demonstrated remarkable stability, retaining 63–83% activity across 30–80 °C after 2 h and 50–70% residual activity between pH 2 and 12 after 6 h. Enzyme activity was enhanced by metal ions (Ca2+, Al³+, Zn2+, Hg2+) and organic solvents, with minimal inhibition at 5 mM of common inhibitory agents. Substrate pretreatment using H2SO4, NaOH, and hot water (60 °C) significantly improved saccharification efficiency. The crude enzyme achieved up to 70% sugar release from coconut husk after 9 h, and 61% for cocoa pod and cassava peel after 6 h, underscoring its strong hydrolytic capacity. These findings highlight the biochemical robustness and industrial relevance of the P. citrinium LHB3 cellulase for efficient valorization of agro-waste and biofuel production.