Isolation of Cellulose Degrading Fungi from Decaying Banana Pseudostem and Strelitzia alba.

L. M. Legodi,E. L. Jansen van Rensburg,I. Ncube,D. La Grange

doi:10.1155/2019/1390890

Abstract

Cellulases are a group of hydrolytic enzymes that break down cellulose to glucose units. These enzymes are used in the food, beverage, textile, pulp, and paper and the biofuel industries. The aim of this study was to isolate fungi from natural compost and produce cellulases in submerged fermentation (SmF). Initial selection was based on the ability of the fungi to grow on agar containing Avicel followed by cellulase activity determination in the form of endoglucanase and total cellulase activity. Ten fungal isolates obtained from the screening process showed good endoglucanase activity on carboxymethyl cellulose-Congo Red agar plates. Six of the fungal isolates were selected based on high total cellulase activity and identified as belonging to the genera Trichoderma and Aspergillus. In SmF of synthetic media with an initial pH of 6.5 at 30°C Trichoderma longibrachiatum LMLSAUL 14-1 produced total cellulase activity of 8 FPU/mL and endoglucanase activity of 23 U/mL whilst Trichoderma harzianum LMLBP07 13-5 produced 6 FPU/mL and endoglucanase activity of 16 U/mL. The produced levels of both cellulases and endoglucanase by Trichoderma species were higher than the levels for the Aspergillus fumigatus strains. Aspergillus fumigatus LMLPS 13-4 produced higher β-glucosidase 38 U/mL activity than Trichoderma species.

Highlights

Cellulose is a simple linear organic polymer of β-1-4 linked glucopyranose units with varying degrees of polymerization (DPs)
These fungal isolates were further screened for endoglucanase activity by culturing on carboxymethyl cellulose (CMC)-Congo Red (CR) agar plates at 30∘C for 72 96 h
The results revealed that all the isolated fungi were able to grow and secrete endoglucanase which hydrolysed CMC bound to CR dye

Summary

Introduction

Cellulose is a simple linear organic polymer of β-1-4 linked glucopyranose units with varying degrees of polymerization (DPs). In primary cell walls the DP range is 5000 – 7500 glucopyranose units, whereas the DP in secondary cell walls is approximately 10000 and 15000 [1]. This polysaccharide is abundantly available in materials, such as agro-wastes, municipal wastes, and forest residues. Cellulases are enzymes with different specificities to catalyse the hydrolysis of glycosidic bonds within cellulose (Jecu, 2000; Khan et al, 2016). The enzymatic hydrolysis of cellulose involves exoglucanases (exo-1,4-β-glucanases, EC 3.2.1.91) endoglucanases (endo-1,4-β-glucanases, EC 3.2.1.4) and βglucosidases (β-D-glucoside glucohydrolase, EC 3.2.1.21) which exhibit high specificity for the β-1.4 glycosidic linkages (Jecu, 2000). Total cellulase is an activity involving the synergistic actions of the above enzymes that is measured using insoluble substrates such as the Whatman No 1 filter paper, cotton linter, microcrystalline cellulose (Avicel), or bacterial cellulose [2]

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