Bioprospecting and characterisation of cellulase producing endophytic fungus, Fusarium annulatum from Caryota urens

Cellulases are a complex system of three enzymes, including endoglucanases, exoglucanases and β-glucosidases, that work together in synergic fashion to degrade lignocellulosic biomass into simple sugars. Despite their enormous applications, they imply high production costs, which represent a significant bottleneck limiting the industrial utilisation. This study therefore investigated the purification and characterisation of cellulase producing endophytic fungal strain, Fusarium annulatum, isolated from Caryota urens (Jaggery palm), identified by morphological characteristics and ITS sequencing. Crude cellulase enzyme was obtained from F. annulatum solid-state fermentation and partial purification of the enzyme was achieved through ammonium sulphate precipitation and dialysis. The partially purified enzyme sample exhibited significant activities of endoglucanase (1.2358 ± 0.0055 IU/mL), β-glucosidase (0.708 0.017 IU/mL) and cellobiohydrolase (0.244 ± 0.019 IU/mL). The filter paper assay of the partially purified enzyme demonstrated significant cellulase activity of 0.7406 ± 0.0258 IU/mL. The optimal pH and temperature of the partially purified enzyme were determined to be 6.0 and 50.0 °C, respectively. These results demonstrate the cellulase producing capacity of F. annulatum, anticipating its industrial production for various purposes, such as biomass conversion and biofuel production. This is one of the first reports of cellulase activity by F. annulatum.