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Figure Above: The reduction of iron by low molecular weight chelators produced by fungi (here represented by 2,3 dihydroxy benzoic acid), in the presence of peroxide, will generate hydroxyl radicals via the Fenton reaction. Superoxide is also generated in this mechanism as this data from Elecrtron Spin Resonance shows.
Figure below: Brown rot degradation of wood. The reminants of fungal hyphae cling to a wood cell wall undergoing degradation. Bore holes from fungal activity are shown in both tangential and radial walls of the wood cell.
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Biofuels, Bioprocessing and Bioconversion:
Bioconversion for Biofuels and other applications: Algae, fungi and
bacteria all can be used (and even combined in series) to produce
different types of products and biofuels.
Biochemical mechanisms involved in the biodegradation of
lignocellulose materials have great value and provide the basis for
research in a number of subfields:
1) Conversion of biofiber to liquid and gaseous biofuels and
chemical feedstocks - Some microorganisms such as wood decay fungi
are ideally suited to depolymerize plant/wood cells to produce the
basic building blocks found in cellulose, hemicellulose and lignin,
and this can be used to advantage with thermochemical
depolymerization. The basic monomeric sugar in cellulose, glucose
can be fermented to produce liquid fuels such as ethanol, but
hydrogen can also be produced using anaerobic organisms. In one
current project in our laboratory we are exploring the use of algae
to produce bio-oil from hexose sugars produced from the
depolymerization of wood polysaccharides by fungi. Other sugars,
such as xylose from hemicellulose can be used to produce other
chemicals and feed stocks. As an example, we are exploring their use
for heterotrophic growth of algae for bio-oil production. Lignin
monomers have a variety of applications, and "brown rotted" lignin
can be used as an adhesive with very little additional modification.
Currently we are involved in a collaborative effort with Italian
scientists exploring production of hydrogen fuels from anaerobic
bacterial fermentation of lignocellulosic residues, and we also are
growing algae heterotrophically and exploring their ability to
assimilate residual sugars for bio-oil production.
2) Remediation of pollutants in waste streams, and contaminants
in soils and water - Our research on free radical mechanisms
involved in lignocellulose oxidation and fungal biodegradation
mechanisms related to the conversion of the cellulosic materials,
has lead to the pilot scale application of our patented chelation
technology for pollutant (acrolein) remediation in waste streams,
and the remediation of recalcitrant dyes.
3) Protecting biomaterials from microbial degradation and
prolonging the durability of bioproducts - Work in this area ranges
from the development of new antioxidant systems for the protection
of wood against the free radical attack mediated by fungi and other
microorganisms, to the conservation of valuable artifacts.
4) Carbon cycling and sequestration in the environment - All
carbon that is fixed as plant material is eventually broken down and
released as CO2 to complete the carbon cycle. Brown rot
fungi produce the derived lignin fraction that accounts for
approximately 1/3 of the carbon residue (humic derivatives) in
coniferous forest floor soil horizons. Understanding the basic
mechanisms involved in the production of these humic substances and
the rate at which this material is converted to either CO2
or to dissolved organic matter is important in global ecosystem
modeling. |
