Biodegradation of oil palm fibers using locally isolated fungi (Pycnoporus sanguineus) through plant biomechanics approach
Utilization of lignocellulosic OPEFB fiber has tremendously seen in Malaysia due to the cellulose and hemicellulose content. Conversion of these biopolymers into valuable products remains a challenging task with the presence of the recalcitrant lignin and scattering silica bodies on the fiber...
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| Format: | Thesis |
| Language: | English |
| Published: |
2017
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/68530/1/FK%202018%2020%20-%20IR.pdf |
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| Summary: | Utilization of lignocellulosic OPEFB fiber has tremendously seen in Malaysia
due to the cellulose and hemicellulose content. Conversion of these biopolymers
into valuable products remains a challenging task with the presence of the
recalcitrant lignin and scattering silica bodies on the fiber surface. Therefore, this
study investigates the mechanical behaviour of the complex lignocellulosic
OPEFB fiber containing silica bodies and provide an in-depth understanding of
the delignification of OPEFB by fungi for further bioconversion into wide range
of biomaterial applications. The microstructure of silica bodies on OPEFB fiber
surface was modelled using finite element method, based on the results obtained
from scanning electron microscope (SEM) images, tensile tests and X-ray
microtomography (micro-CT) images. Silica body geometry, possible
anisotropy/ orthotropy, debonding between the interface of the silica body and
fiber, fiber thickness and presence of vascular bundle in the OPEFB were
investigated through 2D and 3D models and analysed by commercial finite
element software, Abaqus.
In 2D model, silica bodies contribute on integrity or strength of the fiber,
however, in the 3D model, the effect of silica bodies on the elasticity of the fiber
was insignificant when the thickness of the fiber is larger than 0.2 mm. In the
developed representative volume element (RVE) and micro-CT models, the
simulation results show that the difference of the fiber model with and without
silica bodies are larger under shear than compression and tension. However, in
comparison to geometrical effect (silica bodies), lignin, cellulose, and
hemicellulose components of the fiber are responsible for the complex
mechanical and interface behavior of oil palm fibers.Hence, screening and isolation of lignin degrading fungi for deconstruction of
lignin polymer in OPEFB was carried out. About 47 isolated fungi collected from
environmental samples with six fungi were able to decolorize selective agar
media, indicating possible presence of lignin-degrading enzymes; laccase and
peroxidases. The highest producer of ligninolytic enzymes was identified as
Pycnoporus sanguineus which able to utilize raw OPEFB fiber through solid state
fermentation (SSF) with an increment of 1.37 folds of ligninolytic enzymes
production as compared to submerged fermentation (SmF). Optimization study
of different substrate pre-treatments (sodium hydroxide, Soxhlet extraction),
incubation temperatures (20-40°C), ABTS concentrations (0-4%) and substrate
amounts (3-15 g) on ligninolytic enzymes production was carried out. Results
showed that the optimum conditions for P. sanguineus to produce highest laccase
(15.49 U/g) with Klason lignin removal at 7.11% were using extractive-free
OPEFB fiber, incubation temperature at 30°C, supplemented with 4 mM of ABTS
and with 10 g of substrate loading size. Effectiveness of P. sanguineus for OPEFB
degradation was further evaluated with the different ratio of fiber, fungi and
palm oil mill effluent (POME) sludge as inoculum.
The relationship between structural OPEFB fiber degradation and
delignification process by P. sanguineus was studied through tensile testing data,
enzymatic and lignin component data, and micro-CT images. The highest total
lignin loss (35.81%) and total phenolic content produced (78.03%) was
determined at a condition ratio of fiber to fungi (60:40), yielding of laccase and
MnP of 0.18 and 0.02, respectively while production rate of laccase and MnP
were 0.98 U/g/d and 0.11 U/g/d, respectively. Micro-CT results revealed that
the delignification process damaged the fiber based on the volume reduction
data where 14.11% of volume reduction was observed with treated fiber while
11.21% volume reduction was achieved with untreated fiber. It is suggested that
P. sanguineus could be a potential lignin degrader of OPEFB fiber before being
manipulated for other valuable products production. |
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