Determining the Optimal Conditions for Crude Cellulase Production from Fusarium oxysporum Isolated from Native Environments

Cellulase, a key enzyme in breaking down cellulose, has significant applications in biomass, biofuel production, and environmental pollution control. This research investigated the optimization of crude cellulase production from Fusarium oxysporum isolates using solidstate fermentation (SSF). For cellulase production optimization, the fungal isolates were cultured to obtain pure cultures and identified based on genus characteristics. Inoculum was prepared by harvesting spores from Sabouraud dextrose agar (SDA). Solid-state fermentation was conducted with agro-based waste materials, including crushed agroresidues: date cores, wild reed, peanut shells, sunflower scales, corn cobs, banana peel, and sawdust, as substrates. Various parameters, including solid substrates, carbon and nitrogen sources, moisture content, incubation temperature and periods, and inoculum size, were optimized for cellulase production. Enzyme activity was measured by carboxymethyl cellulase (CMCase) and filter paperase (FPase) assays. The results showed that ten isolates of Fusarium spp. were identified, with isolate F4 demonstrating superior cellulase production compared to the others. This isolate was identified as Fusarium oxysporum. F4 isolate exhibited the highest cellulase index (CI) and specific activities for CMCase (17.33 U.mg-1) and FPase (8.62 U.mg-1). The optimal SSF conditions included corn cobs as the substrate, 60% moisture, and ammonium sulfate as the nitrogen source, yielding specific activities of 22.93 U.mg-1 (CMCase) and 10.61 U.mg-1 (FPase). The optimal temperature for cellulase production was 25°C, with peak enzyme activity observed after 120 h of incubation. The study’s findings demonstrated the potential of F. oxysporum for efficient cellulase production, particularly from inexpensive agro-residues, highlighting its industrial and environmental significance.