Lignocellulosic 2011). Certainly, in addition to hemicelluloses, hydrothermal pre-treatment

Lignocellulosic waste is the
structural material used to make plant cell wall, and is the therefore the main
component of plant biomass on Earth. Lignocellulose consist three main
components of cellulose 40%-50%, hemicelluloses 25%-30% and lignin 15%-20% (Chandra
2015). Cellulose is primary constituent of lignocellulosic waste, and is a
polysaccharide composed of ?-1,4 linked D-glucose units. Cellulose is
used for the manufacture of paper and cardboard, and can convert through the
action of cellulase enzymes into glucose monomer, for bioethanol production
(Ahmad et al. 2010). Hemicellulose are branched polysaccharide which are
associated with lignin and cellulose in plant cell wall, consist of other
polysaccharide, principally xylans and mannans, which are closely associated
with the cellulose filaments, and chemically linked with lignin. The major
hemicelluloses in hardwoods is xylans (15%-30% dry weight), a polysaccharide
composed of ?-1,4 linked D-xylose units, which can be substituted with
other monosaccharide units, whereas softwood hemicelluloses contains mainly
glactoglucomannan (15%-20% dry weight), a polysaccharide composed of ?,1-4
linked D-glucose, and D-galactose units (Bugg et al. 2011). Certainly, in
addition to hemicelluloses, hydrothermal pre-treatment of lignocellulosic
material also involves solubilization of extract, small portion of cellulose
and lignin (Vazquez et al. 2007). Hemicelluloses consist of both linear and branched
heteropolymers. It mainly contains ?ve monomeric sugars, namely D-glucose,
D-mannose, D-galactose, D-xylose and L-arabinose linked together by ?-1,4-glycosidic
bonds. Covalent bonding between hemicelluloses and lignin provides additional
strength to the plant. Cellulose and hemicelluloses are present in the form of
insoluble crystalline ?bers that are degradable but the processes very complex
due to the involvement of several enzymatic pathways (Aarti et al. 2015). The
term lignin derives from the Latin word ‘lignum’, which means wood. Lignin is
the most abundant structurally complex aromatic polymer
possessing a high molecular weight
and the most recalcitrant, containing of numerous biologically stable linkages. After cellulose, lignin is the second most abundant
renewable biopolymer in nature because of the low
biodegradability of lignin and
large lignocellulosic waste generated through various industries such as paper
and pulp, timber, distillery etc causes a serious pollution and toxicity
problem in aquatic ecosystem.

        For this reason, studies on the
bacterial degradation were more preferable for lignocellulosic waste and the
production of bacterial ligninolytic enzymes has seen increased in recent year
(Renugadevi et al. 2011). Lignin degrading enzymes are essentially
extracellular in nature due to the large and complex structure of lignin which
cannot enter the cell for intracellular action (Sasikumar et al. 2014). Lignin
peroxidase enzymes is useful in the treatment of industrial waste and other
xenobiotic as it has bioremediation potential to decolorize the effluents (Shi
et al. 2013). Over the years, four enzymatic activities have been reported to
depolymerize lignin in decaying plant cell walls like lignin peroxidases
(LiPs), manganese peroxidases (MnPs), versatile peroxidases (VPs) and laccases.
These enzymes have gained attention as potential biological catalysts for lignin
biodegradation and other organic pollutants. Of note, ligninolytic enzymes are
too large to penetrate into undecayed wood cell walls therefore reactive oxygen
species could be the agents responsible for local lignin decay (Pollegioni et
al. 2015). Certainly, the process of lignin degradation is enhanced by several
additional and accessory microbial enzymes, and some of them are now available.

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