The use of FTIR to detect lignin decomposition by mushroom forming fungi under different concentrations and types of nitrogen
(2021) BION02 20201Degree Projects in Biology
- Abstract
- Wood decay fungi are often classified as either brown rot or white rot, depending on their mechanism of accessing nutrients in wood. This dichotomy assumes that white rot fungi break down lignin with various enzymes, while brown rot fungi leave it mostly unmodified and instead bypass it with diffusion of small molecules to reach the desired hemicellulose and cellulose. The effect of different sources and concentrations of nitrogen on this process is uncertain and variable. This study used Fourier Transformation Infrared (FTIR) spectroscopy to monitor the modification of a lignin solution over time, in four different nitrogen treatments, by four white rot and four brown rot fungi. It found that the most modification to lignin media was done... (More)
- Wood decay fungi are often classified as either brown rot or white rot, depending on their mechanism of accessing nutrients in wood. This dichotomy assumes that white rot fungi break down lignin with various enzymes, while brown rot fungi leave it mostly unmodified and instead bypass it with diffusion of small molecules to reach the desired hemicellulose and cellulose. The effect of different sources and concentrations of nitrogen on this process is uncertain and variable. This study used Fourier Transformation Infrared (FTIR) spectroscopy to monitor the modification of a lignin solution over time, in four different nitrogen treatments, by four white rot and four brown rot fungi. It found that the most modification to lignin media was done by C. subvermispora (WR), W.cocos (BR) and B. adusta (WR), in a C/N ratio of 20 (the higher condition), of NH4+ for C. subvermispora and W. cocos, and NO3- for B. adusta. The FTIR spectra also indicate that the two WR species were using a different mechanism to modify the lignin to W.cocos, which could have relied on Fenton chemistry. P. strigosozonata, S. hirsutum, F. pinicola and G. trabeum all make very similar changes to the lignin medium, despite the first two being WR and the latter two BR. C. puteana (BR) was the final species and predictably made almost no changes to the lignin medium compared to the control. Our hypothesis that higher levels of accessible nitrogen would inhibit lignin degradation was not met and in most cases the opposite was true; most species made more modification to the lignin medium in NH4+, and some strongly favoured C/N20 (high nitrogen condition). This study demonstrates the variability between preferred conditions, and in the extent to which different species degrade lignin regardless of decay strategy. WR/BR classification could not predict lignin modification through the changes seen in FTIR spectroscopy, which revealed more of a gradient of modifications rather than a dichotomy. The advantages and limitations of using this technique to examine complex solutions are also evaluated. (Less)
- Popular Abstract
- Rotten to the core; Fungal degradation of lignin
My thesis research has been looking at how different species of fungus degrade lignin in different conditions. Lignin is a complex organic polymer used for structural support in plant material. Wood decomposing fungi are essential in ecosystems to breakdown the wood of trees and recycle the carbon locked within them back into the soil and the air, for use by plants and microorganisms. This process occurs slightly differently depending on the fungus species and their environment. This in turn effects the rate of decomposition and the by-products of the carbon cycle.
There are a few categories of wood degrading fungi, and two of them are white rot (WR) and brown rot (BR). To access... (More) - Rotten to the core; Fungal degradation of lignin
My thesis research has been looking at how different species of fungus degrade lignin in different conditions. Lignin is a complex organic polymer used for structural support in plant material. Wood decomposing fungi are essential in ecosystems to breakdown the wood of trees and recycle the carbon locked within them back into the soil and the air, for use by plants and microorganisms. This process occurs slightly differently depending on the fungus species and their environment. This in turn effects the rate of decomposition and the by-products of the carbon cycle.
There are a few categories of wood degrading fungi, and two of them are white rot (WR) and brown rot (BR). To access nutrients and sugars in wood, they need to bypass lignin. It is sometimes assumed that white rot species will degrade lignin using enzymes, while the brown rot species will modify it, but not break it down. BR species are thought to circumvent lignin by diffusing small molecules past it, or to use a non-enzymatic system to changes its structure; Fenton chemistry. The Fenton reaction is thought to be less effective and attacks lignin using hydroxyl radicals (.OH).
My study takes four white rot and four brown rot species, and looks at the different effects they have on a defined lignin medium (LM). The conditions in which the fungi are living also has an effect on how effectively they degrade lignin. Specifically, I looked at nitrogen conditions. I used two types of nitrogen which were ammonium (NH4+) and nitrate (NO3-). NH4+ is generally known as the more accessible source of nitrogen. I also used two concentrations of nitrogen; low and high. Each of my species was incubated in a lignin solution of each of the four nitrogen conditions; high NH4+, low NH4+, high NO3- and low NO3-. High concentrations of nitrogen have been reported to inhibit the lignin breakdown by some white rot fungi, but this changes depending on the nitrogen source, and too little nitrogen will not allow any fungal functioning at all. One of the aims of my research was to see if there was any trend in optimum conditions for lignin degradation in these two categories of species. There were three replicates, and the solution was sampled at four time points determined by growth diameter. The samples were then analysed with Fourier Transformation Infrared Spectroscopy (FTIR). This produces spectra which show what type bonds of between which atoms are present, and also quantitative information about the chemical structures present.
The three species that made the most changes to the LM were Ceriporiopsis subvermispora (WR), Bjerkandera adusta (WR) and Wolfiporia cocos (BR). Two of these, C. subvermispora and B.adusta, are white rots so it was expected that they would degrade lignin, therefore change the solution, the most. W. cocos is a brown rot so the high amount of change to the LM, indicating lignin breakdown, was unexpected. The spectra indicated that it was using Fenton chemistry because some features could have represented reagents of the reaction. Four of the other species showed similar effects on the solution even though two were white rot and two were brown. There was however a distinct feature that appeared only in the white rot species. The reactions to the nitrogen conditions was varied. Most species showed a slight preference for low NO3, but W. cocos and C. subvermispora made the most changes to the lignin spectra in high NH4+. B. adusta appeared most active in high NO3-.
This study supports the idea that extensive lignin breakdown can be present in a BR species, and that white rot species aren’t all good lignin degraders, showing the diversity among groups. It has differentiated the efficient lignin degraders within our eight species, and shown the variety of responses to different nitrogen sources and concentrations.
Masters degree project in Biology – 45 cr
Department of Biology, Lund University
Advisor: Dimitrios Floudas
Department of Microbial Ecology (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9041715
- author
- Casey, Stephanie
- supervisor
- organization
- course
- BION02 20201
- year
- 2021
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9041715
- date added to LUP
- 2021-03-11 14:47:17
- date last changed
- 2021-03-11 14:47:17
@misc{9041715,
abstract = {{Wood decay fungi are often classified as either brown rot or white rot, depending on their mechanism of accessing nutrients in wood. This dichotomy assumes that white rot fungi break down lignin with various enzymes, while brown rot fungi leave it mostly unmodified and instead bypass it with diffusion of small molecules to reach the desired hemicellulose and cellulose. The effect of different sources and concentrations of nitrogen on this process is uncertain and variable. This study used Fourier Transformation Infrared (FTIR) spectroscopy to monitor the modification of a lignin solution over time, in four different nitrogen treatments, by four white rot and four brown rot fungi. It found that the most modification to lignin media was done by C. subvermispora (WR), W.cocos (BR) and B. adusta (WR), in a C/N ratio of 20 (the higher condition), of NH4+ for C. subvermispora and W. cocos, and NO3- for B. adusta. The FTIR spectra also indicate that the two WR species were using a different mechanism to modify the lignin to W.cocos, which could have relied on Fenton chemistry. P. strigosozonata, S. hirsutum, F. pinicola and G. trabeum all make very similar changes to the lignin medium, despite the first two being WR and the latter two BR. C. puteana (BR) was the final species and predictably made almost no changes to the lignin medium compared to the control. Our hypothesis that higher levels of accessible nitrogen would inhibit lignin degradation was not met and in most cases the opposite was true; most species made more modification to the lignin medium in NH4+, and some strongly favoured C/N20 (high nitrogen condition). This study demonstrates the variability between preferred conditions, and in the extent to which different species degrade lignin regardless of decay strategy. WR/BR classification could not predict lignin modification through the changes seen in FTIR spectroscopy, which revealed more of a gradient of modifications rather than a dichotomy. The advantages and limitations of using this technique to examine complex solutions are also evaluated.}},
author = {{Casey, Stephanie}},
language = {{eng}},
note = {{Student Paper}},
title = {{The use of FTIR to detect lignin decomposition by mushroom forming fungi under different concentrations and types of nitrogen}},
year = {{2021}},
}