Characterization of an endo‐beta‐1,4 glucanase gene from paper‐degrading and denim bio‐stoning cellulase producing Aspergillus isolates

Abstract

Cellulases are used in textile, pulp and paper, brewery and wine, sugars, and ethanol industries. Four fungal isolates obtained from organic municipal solid wastes (OMSW) were selected based on their cellulolytic activity on carboxymethyl cellulose (CMC) agar medium. Based on the internal transcribed spacer (ITS) sequence of the ribosomal DNA, the four cellulolytic isolates were identified as Aspergillus fumigatus AKAL1, Aspergillus oryzae AKAL4, Aspergillus flavus AKAL8, and Aspergillus flavus AKAL9. After 9 days of fermentation at 30°C and pH 6.5 under 110 rpm agitation, these isolates produced the maximum amount of cellulase. The cellulase showed optimum activity at temperature 35–40°C and pH 6.0–7.0 and was stable for 1 h at 25–45°C and pH 5.0–7.0. The Mg2+ and Zn2+ significantly increased but Hg2+, K+, and Ca2+ severely repressed the cellulase activity. Degradation of filter papers and bio‐stoning of denim was successfully done with the crude cellulase. An endo‐β‐1,4‐glucanase was isolated and characterized from Aspergillus isolates. Genome‐wide analysis revealed that the genomes of A. oryzae, A. fumigatus, and A. flavus, the pertinent species of the fungal isolates, had 23, 25, and 22 cellulase genes, respectively. Phylogenetic analysis revealed that the cellulases in these fungal species were divided into three major groups, and the isolated endo‐β‐1,4‐glucanase clustered to Group II. Ten different motifs are present in cellulases of the three species. Results herein provide a valuable resource for understanding cellulase genes in Aspergillus species and potential application of cellulase in textile and fermentable sugars production industries.