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|Title: ||Evaluation of some wood rotting fungi for bagasse pretreatment in ethanol production|
|Authors: ||Dawit, Tewolde|
|Advisors: ||Amare Gessesse (Ph.D)|
|Copyright: ||Jun-2011 |
|Date Added: ||4-Jul-2012 |
|Publisher: ||Addis Ababa University|
|Abstract: ||Lignocellulosic biomass is a sustainable feedstock for ethanol production compared to other
substrates. In the ethanol generation process, pretreatment makes cellulose more accessible to
enzymatic hydrolysis by modification of the lignin barrier. Biological pretreatment employs
selective rot fungi that preferentially degrade lignin with minimum loss of polysaccharides.
The system is not well developed; but is advantageous over other pretreatments because
reactions are enzymatic. These fungi produce ligninolytic enzymes, predominantly lignin
peroxidase (LiP), manganese peroxidase (MnP) and laccase (Lac) in different combinations.
Studies on biological pretreatments have shown lignin weight loss and improvement in
ethanol yield. However, only few well characterised white rots have been explored. The aim
of this study was to evaluate the potential of 15 wood rotting fungi isolated from Ethiopia for
pretreatment during 15 days solid state fermentation, using bagasse as lignocellulosic
substrate. The production of ligninolytic enzymes by Fomitiporia aethiopica, F.
pseudopunctata, Fomitopsis carnea and Vanderbylia vicina were reported for the first time in
this study. The white rots, F. aethiopica, Perenniporia tephropora, Inonotus sp. and
Pleurotus sajor-caju, were identified as relatively highly selective based on maximum and
minimum productivity of ligninolytic and polysaccharide degrading enzymes, respectively.
The pretreatment by the white rots caused ligninolysis and better cellulose digestibility was
obtained with higher lignin loss. Among the selective degraders, P. tephropora caused the
highest lignin loss (7.71%) and cellulose digestibility (29.44 %) after enzyme hydrolysis of
the pretreated bagasse. This digestibility showed an improvement by 38.74 % in comparison
with untreated bagasse. In addition to high MnP productivity (55.87 U/g), P. tephropora also
produced high titers of Lac (79.65 U/g) in contrast to the other selective degraders that might
have attributed to better lignin loss. The ethanol yield from fermentation of cellulase enzyme
hydrolysed P. tephropora pretreated bagasse was 1.87 g/L, which was an improvement by
27.21 % compared with untreated bagasse (1.47 g/L). Therefore, P. tephropora pretreatment
enhances ethanol production from bagasse through partial degradation of lignin, which
improves the accessibility of cellulose to enzyme hydrolysis.|
|Description: ||A thesis submitted to the School of Graduate Studies, Addis Ababa University
in partial fulfilment of the requirements for the Degree of Master of Science in
|Appears in:||Thesis - Biology|
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