Effect of white rot fungi variation on the biopulping of oil palm trunk
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Date
2014-08
Authors
Singh, Pooja
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Abstract
Lignocelluloses biomass is an important and sustainable natural resource for paper
making. Wood the predominant source consists of flexible cellulose fibres, its
pretreatment makes cellulose more accessible to enzymatic hydrolysis by
modification of the lignin. Biological pulping is the treatment of lignocellulosic
materials with oxidative lignin-degrading white rot fungi prior to pulping process.
These microorganisms secrete enzymes that degrade lignin with minimum loss of
polysaccharides. Though this pretreatment system is not well developed; but is
advantageous over others because it does not burden the environment with harmful
chemicals. Studies on biological pre-treatment have shown lignin loss, weight loss
and improvement in paper quality. In the present study evaluation of the potential of
four different white rot fungi namely Phanerochaete chrysosporium Burds, Trametes
versicolor, Pycnoporus sanguineus (KUM70097) and Schizophyllum commune
(KUM 793066) was conducted. They were chosen as they are well known inhabitant
of tropical decomposing trees. The interest was to cultivate them on oil palm trunk as
lignocellulosic substrate using solid state fermentation and determines their effect on
paper making. After 28 days of pretreatment at 28±2°C with initial moisture content
of 60% and constant aeration, the chips were harvested. Standard TAPPI methods,
commonly used by the paper and pulp industry, were employed to determine the
percentage cellulose, Klason lignin and extractives in the chips. These fungi produce
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ligninolytic enzymes, predominantly manganese peroxidase (MnP), lignin
peroxidase (LiP), and laccase (Lac) in different combinations. The results supported
the findings of others that white rots Phanerochaete chrysosporium, Trametes
versicolor, Pycnoporus sanguineus and Schizophyllum commune can grow upon
lignocellulosic substrates and produce considerable refining energy savings. The
weight, lignin, cellulose and holocellulose loss was calculated and the extent of cell
wall breakdown in combination with lignin modification was depicted from
Scanning electron microscopy(SEM).The extent of bio delignification clearly shows
the advantage of fungal pre-treatment in biopulping enhances production of
enzymes, causing partial degradation of lignin and improving accessibility of
cellulose. Additionally this study puts in evidence that oil palm biomass is a suitable
substrate for biopulping and has potential for use in large-scale biotechnological
processes. Considering all the four fungi and their performance overall in pulping
and papermaking properties, Trametes versicolor can be considered to be the best
amongst them. This fungi shows peak activities of lignocellulytic enzymes and in
mechanical refining the chips pre-treated with T.versicolor consumed the least
energy. After refining when pulp properties were studied it depicted that most of the
mechanical properties were superior except for brightness. The Scanning electron
microscopic examination revealed the development of cracks and collapse of cell
walls. Thus due to afore mentioned qualities T.versicolor is found to be ideal for
biopulping.
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Keywords
White Rot