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Mechanisms of lignocellulosic conversion by the brown rot fungus serpula lacrymans
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Nurika, Irnia (2013) Mechanisms of lignocellulosic conversion by the brown rot fungus serpula lacrymans. PhD thesis, University of Warwick.
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WRAP_THESIS_Nurika_2013.pdf - Submitted Version Download (6Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b2698866~S1
Abstract
Cost effective processing of wheat straw using solid state fermentation (SSF)
would provide a source for value added chemicals from agricultural waste biomass.
Fungi natural breakdown lignocellulosic biomass hence could have received a lot of
attention. In this study the ability of S. lacrymans to convert straw waste was
compared with other Basidiomycetes (Postia placenta, Phanerochaete
chrysosporiom, and Schizophyllum commune). S. lacrymans out performed the other
Basidiomycetes both in its growth (as measured by ergosterol and fatty acid
production (linoleic acid);18:2n6c) , and in the comounds released which included;
total soluble phenols, total reducing sugars, and low molecular organic chemicals
(MW<400).
Non-enzymatic breakdown requiring the presence of Fe2+ was also
demonstrtated and influenced by the production of quinone and low molecular
organic acid. The amount of the fungal extract used and the concentration of
chelator/reducing agents also affected the production of Fe2+. Changes in the
lignocellulose structure was also detected as key functional group, such as the
pyranose ring and aromatic skeletal vibration were significantly reduced following
culture with S. lacrymans and a significant reduction in mass was measured.
Iron reductase genes IR1 and IR2 suspected to be involved in the
lignocellulose degradation were cloned. It seems that these genes are more closely
related to the cellulose binding module (CBM) family instead of cellobiose
dehydrogenase (CDH) genes as first suspected. IR1 has an open reading frame of 774
bp which encoding 258 amino acid (55 kDa), whilst IR2 642 bp encoding 214 amino
acid ( 49 kDa). The IR1 gene contains a CBM1 domain which is lacking in IR2. Gene
expression analysis using qRT-PCR showed that in the early stage of fungal growth,
the level of IR2 genes expression was higher than IR1 while IR1 became more
dominant in the latter stages of culture. The time at which these genes are highly
expressed correlated with the release of soluble and aromatic phenolic compounds.
The functionality of the recombinant IR1 and IR2 on the decomposition of
lignocellulose was shown using several assays including; iron reductases, nitrated
lignin and the reduction of electron acceptor (DCPIP). In addition, using both
synthetic and nature sources of cellulose or lignocellulose (Avicel and wheat straw
powder) the recombinant IR proteins were shown to break down cellulose. This
suggested that these enzymes represent a significant addition to those currently used
within biomass based biorefineries
Item Type: | Thesis (PhD) |
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Subjects: | Q Science > QK Botany T Technology > TP Chemical technology |
Library of Congress Subject Headings (LCSH): | Lignocellulose, Solid-state fermentation, Serpula lacrymans, Reduction (Chemistry), Biomass -- Refining, Biomass conversion |
Official Date: | November 2013 |
Institution: | University of Warwick |
Theses Department: | School of Life Sciences |
Thesis Type: | PhD |
Publication Status: | Unpublished |
Supervisor(s)/Advisor: | Barker, Guy C.; Bugg, Tim |
Sponsors: | Indonesia. Direktorat Jenderal Pendidikan Tinggi [Directorate General of Higher Education] (DIKTI); Indonesia. Departemen Pendidikan Nasional [Ministry of National Education] |
Extent: | xix, 252 leaves : charts. |
Language: | eng |
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