Studies on cellulases of some cellulose-degrading soil fungi.

Abstract

In this study, novel cellulolytic fungal strains were isolated, purified, and identified. The ability of these isolates to biodegrade cellulosic materials was examined. The potential of the isolates to produce cellulolytic enzymes and optimize the cellulose degradation process was also investigated. The nylon net bag technique was used to separate cellulose-degrading fungi from soil. A total of 37 species were isolated and tested for their capacity to break down rice straw as a cellulose source. Qualitative assays for cellulase were carried out by Congo red plate assay, while quantitative assays were carried out using the dinitrosalicylic acid (DNS) method at 546nm. Following morphological and molecular identification, the isolates that exhibited the highest cellulase activities were identified as Neurospora intermedia (Assiut University Mycological Center (AUMC) 14359), Fusarium verticillioides (AUMC 14360), and Rhizopus oryzae (AUMC 14361). For N. intermedia, the optimal conditions for maximum activity were a 2% carboxymethylcellulose (CMC) concentration, beef extract and peptone as nitrogen sources, pH 7, 30°C, and an inoculum size of 2.5 (v/v). For F. verticillioides, the optimal conditions were 2.5% CMC concentration, yeast extract as a nitrogen source, pH 6, 30°C, and an inoculum size of 2 (v/v). For R. oryzae, the optimal conditions were 2% CMC concentration, beef extract as a nitrogen source, pH 7, 30°C and an inoculum size of 2.5 (v/v). The identified strains represent new starter strains with high efficiency under optimum conditions for prospective large-scale application in cellulose degradation and nanocellulose production-dependent water purification.