Biology of Trichoderma sp. isolated from polluted sediment and its potential in degradation of phenanthrene (PAHs)
Polycyclic Aromatic hydrocarbons (PAHs) as contaminants are one of the most recalcitrant, persistent organic compounds and this has made their fate in the environment of significant interest. PAHs have become a great concern as they are highly ecotoxic with potential of being human carcinogens, m...
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| Format: | Thesis |
| Language: | English |
| Published: |
2014
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/70588/1/FS%202014%2080%20IR.pdf |
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| Summary: | Polycyclic Aromatic hydrocarbons (PAHs) as contaminants are one of the most
recalcitrant, persistent organic compounds and this has made their fate in the
environment of significant interest. PAHs have become a great concern as they are
highly ecotoxic with potential of being human carcinogens, making their rapid
elimination and detoxification from the environment of necessary importance. This
study aimed to isolate and screen indigenous soil and sediment fungi for possible
application in the remediation of these contaminants. It also aimed to investigate how
two important factors, temperature and pH influence the PAHs degradative capability
of the potent fungus using phenanthrene as a model substrate. The study also
involves evaluating the suitability of this isolate in qualitative phenanthrene
degradation through the detection of metabolites. Soil and sediment samples were
collected for fungal isolation. Forty-four isolates were obtained and screened to
select the best isolate with the potential to degrade phenanthrene as a substrate.
Trichoderma sp., a filamentous Sordariomycetes isolated from Bagan Lalang
sediment showed the best phenanthrene tolerance with a high growth percentage of
76.9% at 72 hrs and a percentage phenanthrene degradation of 60.4% after 10days of
incubation in liquid mineral medium. Evaluation of the effects of environmental
factors on phenanthrene degradation showed that both parameters (temperature and
pH) had a significant effect on the fungus ability to degrade phenanthrene.
Laboratory studies using Mineral Salt Broth (MSB) showed that phenanthrene
degradation efficiency was influenced by temperature with the highest degradation of
69.5% occurring at 35°C. This temperature also supported a good biomass
accumulation of 62mg dry weight. Less phenanthrene degradation was observed at
lower and higher temperatures. Influence of pH on substrate degradation showed
thatthe optimum pH for phenanthrene degradation by the fungus was at a neutral pH
7. This pH point facilitated both effective phenanthrene degradation of 76.8% and
biomass growth of 48mg dry weight thus, making it evident that higher rates of
degradation was somewhat related to a high biomass growth. Qualitative analyses by
GC-MS of extracts after incubation showed that Trichoderma sp. could degrade
phenanthrene; yielding metabolites such as 9,10-dihydro-9,10-
dihydroxyphenanthrene, 9,10-dihydrophenanthrene, 9-Phenanthrol, 1,2,3,4- tetrahydrophenanthrene and phthalic acid. Based on the detected metabolites, the
mechanism of phenanthrene degradation by this fungus, suggests the activities of
both ligninolytic and non-ligninolytic type of enzymes with major attack on the Kregion
(C-9 and C-10) of phenanthrene. The metabolite 1,2,3,4-
tetrahydrophenanthrene detected in culture extracts suggests that another pathway
utilized by the fungus may exist in substrate degradation. Thus, this Trichoderma
isolate could serve as a potential innoculum that can be utilized in microbial PAHs
degradation and environmental factors such as pH and temperature does have an
influence on the strains ability to act on phenanthrene. |
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