Hyper-Productivity, Characterization, and Exploitation of a Cellulase Complex from a Novel Isolate of Aspergillus tubingenesis S2 using Lignocellulose-based Material

Abstract

The hyper-production potential of a cellulase complex from a local strain of Aspergillus tubingensis S2, indigenously isolated from rotten tomato, was investigated. A total of nine fungal species of Aspergillus and Trichoderma were isolated and confirmed through triple-phase screening via 18S ribosomal DNA sequencing and construction of a phylogenetic tree. Congo red testing and the zone of clearance method were used to confirm the cellulase production from A. tubingenesis S2 isolate. A. tubingenesis S2 revealed maximum cellulase production (78 µg/mL/min) and was selected for further study. The optimum fermentative conditions, including the incubation period, pH, and temperature values, were determined to be 96 h, pH 4.8, and 40 °C, respectively, for obtaining the cellulase activity of 86.4±2.1 µg/mL/min. The cellulase was 5.14-fold purified by ammonium sulfate fractionation and gel permeation chromatography. Characterization revealed that maximum activity (130.5 µg/mL/min and 133.5 µg/mL/min) was achieved at 4.5 pH and 40 °C, respectively. A monomeric protein with an apparent molecular weight of 76 kDa was evident after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cellulase revealed maximal activity with 40-mesh size corn stover as compared with 20-mesh size corn stover and 80-mesh size corn stover after 36 h of incubation at 40 °C.