3.2 Enzymes in Endophytic Fungal Remediation
Endophytic fungi produce enzymes such as amylases, lipases, proteases, etc., as
part of their mechanism to overcome the defence of the host against microbial
invasion and to obtain nutrients to their development (Sunitha et al. 2012 ; Torres
et al. 2003 ). Naturally, endophytic fungi play an important role in global carbon and
nitrogen cycling by promoting the bioconversion of organic matter through enzy-
matic and non-enzymatic systems. In forest region, the endophytes breakdown
wood polysaccharides using a combination of enzymes which break glycosides
linkages between B-D-xylopyranosyl and glucopyranosyl residues using cellulase
system consists of three classes of enzymes, i.e. 1,4-b-D-glucan cellobiohydrolases,
endo-1,4-b-D-glucanases and 1,4-b-D-glucosidase (Rodrigues et al. 2011).
Phenol oxidase enzymes which include peroxidases, laccases and tyrosinases
degrade lignin which is a hydrophobic polymer thatfills up the space between the
cellulose microfibrils and laccases are the copper containing oxidases that have the
ability to oxidize substrates with high redox potential in the presence of synthetic
mediators which allow the degradation of non-phenolic lignin. Lignin peroxidase
and manganese peroxidases are described as true ligninases because of their high
redox potential. Some researchers stated that on the role of Xylariaceous endophytic
fungi simply waiting for their host to senesce to begin the decomposition of the host
cell wall material (Petrini and Petrini 1985 ; Rodrigues et al. 2011). Several endo-
phytic fungi are known to produce lignocellulolytic enzymes (Suryanarayanan et al.
2009 ). Lignin is a heterogenous and irregular arrangement of phenyl propanoid
polymer protects cellulose from chemical or enzymatic degradation. Fungi produce
extracellular enzymes to cleave the aryl–a-carbon bond or bond between thea- and
b-carbons of the alkyl chain radical in lignin (Karsten 2008 ). Shi et al. ( 2004 )
demonstrated that adding endophytic fungiPhomopsissp. to scantly decompose
straw by degrading lignin. In another study, laccase and peroxide produced by
endophytic fungi contribute directly to the decomposition of litter lignin (Dai et al.
2010 ).
Nutritional and environmental stress may induce fungal relative enzymatic gene
express, and then change endophytic fungal metabolic pathway (Chen and Dai
2013 ). The synergetic metabolism of endophytic (Basidiomycetes) and soil fungi
transform stable polymers to other simple compounds such as CO 2 , humus sub-
stance and glycoproteins (Granit et al. 2007 ; Talbot et al. 2008 ).
Rodrigues et al. (2011) reported that a basidiomycete and a deuteromycete
corresponding to mycelia sterile isolated from the Chilean native treesPrumnopity
sandinaand an unidentified basidiomycete and mycelia sterile fromDrimys winteri
had lingo-cellulolytic activity thus promoted the wood biodegradation. Researchers
reported that the lignocellulosic materials were degraded by fungal enzymes on two
systems (a) hydrolytic system consisting xylanases and cellulases and (b) unique
oxidative ligninolytic system comprises laccases, ligninases and peroxidases
(Correa et al. 2014 ).
50 Y.L. Krishnamurthy and B.S. Naik