Optimization and characterization of extracellular cellulase produced by native Egyptian fungal strain

Abstract

Since accumulation of agricultural wastes represents a huge problem, it was important to explore the available methods to help eliminate agricultural wastes safely, and simultaneously produce functional enzyme like cellulase. Six native Egyptian fungal strains were isolated, morphologically identified and screened for cellulose biodegradation potential, which was determined as endoglucanase or as carboximethylcellulase (CMCase). The most promising isolate (Aspergillus terreus) was selected for molecular characterizations based on sequencing of internal transcribed spacer (ITS). Further optimization experiments were accomplished on the selected strain. The strain with cellulolytic activity, 2.26 IU mL-1 was identified using ITS nucleotides (genes) sequences and the result confirmed that the strain is 99.8% homology with A. terreus. Then, it was submitted to GeneBank and given an accession number. Further optimization experiments revealed that 35°C is the optimum temperature for cellulase production and raised the enzyme activity (EA) up to 3.19 IU mL-1. Out of two organic nitrogen sources; peptone at concentration 6 gL-1 was found to be the optimum nitrogen source for cellulase production with the highest activity 4 IU mL-1. Whereas, the different four carbon sources: microcellulose, corn stalks, wheat straw and rice straw showed significant differences in EA with values 11.07, 9.68, 7.87 and 3.71 IU mL-1, respectively at pH 3. The maximum EA was recorded to be within 5-7 days of incubation, dependent on type of carbon sources. The optimization of different incubation conditions raised cellulolytic activity from 2.26 IU mL-1 up to 11.18 IU mL-1.