Screening and detection of extracellular cellulases (endo- and exo-glucanases) secreted by filamentous fungi isolated from soils using rapid tests with chromogenic dyes

The screening plate method is commonly used for previous detection of cellulases produced by micro-organisms with biotechnological potential. In this manuscript, the authors aim to evaluate the hydrolytic ability of different fungi isolated from soil for the production of cellulolytic enzymes for cellulose degradation and determining the enzymatic index (EI) in relation to the growth of fungal colony and halo. The fungi were grown in carboxymethyl cellulose medium (CMC 1% w/v) and Avicel medium (Cellulose microcrystalline 1% w/v) for the determination of endo-glucanases and exo-glucanases respectively at 28°C for 48 h. Four chromogenic dyes were used: Congo Red, Phenol Red, Trypan Blue and Gram’s Iodine. Also, another screening method was compared using carboxymethyl cellulose medium (CMC 1% w/v) at 28°C for 96 h and exposed with Congo Red dye in buffer Tris HCl 0.1 M, pH 8.0. The results obtained allowed to find significant differences between the tested fungi, the growth time and chromogenic dyes. The strains with higher Enzymatic Index (EI) were JCO1, UFT1, UFT2 and UFT3 for endo-glucanases and JCO2, UFT1, UFT2 and UFT3 for exo-glucanases.Keywords: Cellulases, chromogenic dyes, filamentous fungi, endo-glucanase, exo-glucanase.African Journal of Biotechnology, Vol 13(52) 4694-470