Isolation and screening of efficient ligninolytic fungi
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Date
2013
Authors
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Publisher
CCSHAU
Abstract
Lignin, the most abundant aromatic biopolymer on earth, is extremely recalcitrant
to degradation. By linking to both cellulose and hemicellulose, it creates a barrier to any
chemicals or enzymes and prevents the penetration of lignocellulolytic enz ymes into the
interior lingocellulosic structure. Lignin is the major hurdle in the degradation of
lignocellulosic biomass. It is degraded by an enzyme complex containing three enzymes
namely laccase, manganese peroxidase and lignin peroxidase that are collectively known as
ligninases. These enzymes are produced by several microorganisms, commonly by fungi but
most of them have high production cost and no efficiency in enzyme production and its
enzyme activit y. Therefore in the present investigation, a total of 24 mutually distinct fungi
were isolated from different ecological niches such as leaf and litter waste, garbage
dumpin g site, mushr oom waste, compost, ver micompost, paper and pulp waste and biogas
slurry. Out of these 24 fungal isolates, 16 fungal cultures were screened as ligninolytic
fungi by observing the formation of zone of clearance on malt extract agar plates containing
aniline blue dye and tannic acid. The zone of clearance ranged from 1.03 to 1.20 Isolate
HST15 formed the largest zone of clearance of 1.20. The fungal isolate, HST9 was showing
highest laccase (15.5 U/ml) and Manganese peroxidase (4 U/ml) activity among the isolates
while maximum lignin peroxidase activity was observed in HST15 (21U/ml). On the basis
of lignin peroxidase activity, HST15 was selected as the best ligninolytic fungal isolate.
The selected fungal isolates were morphologically identified on the basis of their hyphae,
sporangiophore and spores. Among the five best fungal isolates, three were identified to be
ascomycetes and two were basidiomycetes.
Description
Keywords
Lignin, Fungal isolate, Ligninolytic enzyme, Ligninases, Laccase, Manganese peroxidase, Lignin peroxidase