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Laccase from a Litter Degrading Fungus: Evaluation for Environmental Applications and Modification of Lignin to a Bioadhesive

Ibrahim, Victor LU (2011)
Abstract (Swedish)
Popular Abstract in Swedish

The phenol oxidase “laccase” was first described towards the end of the 19th century from the wound

sap of the lacquer tree Rhus vernicifera. However, its use in one of the oldest biotechnologies, i.e. the

making of lacquerware in East-Asia, dates back to 5000-6000 BC. The enzyme has the widest

distribution in nature among the multicopper oxidases. It catalyzes one electron transfer oxidation in

the presence of molecular oxygen producing water as by-product. Based on these highly desired

oxidative properties and its wide range of substrates, immense efforts have marked the last decades

regarding the search for new enzyme sources and potential... (More)
Popular Abstract in Swedish

The phenol oxidase “laccase” was first described towards the end of the 19th century from the wound

sap of the lacquer tree Rhus vernicifera. However, its use in one of the oldest biotechnologies, i.e. the

making of lacquerware in East-Asia, dates back to 5000-6000 BC. The enzyme has the widest

distribution in nature among the multicopper oxidases. It catalyzes one electron transfer oxidation in

the presence of molecular oxygen producing water as by-product. Based on these highly desired

oxidative properties and its wide range of substrates, immense efforts have marked the last decades

regarding the search for new enzyme sources and potential laccases that are suitable for different

applications.

In the present thesis, we introduce a litter degrading fungus from Galerina sp. as a laccase producer.

Besides laccase, the isolate is capable of producing lignin and manganese peroxidases as lignin

modifying enzymes. The fungus has the ability to grow on different agricultural residues in

submerged and solid state fermentation and to produce high amounts of laccase, especially after

induction.

The physical and biochemical characteristics of the major laccase, purified by chromatographic means

from the crude culture supernatant, are treated in details. Sequences of internal peptides confirm the

identity of the purified protein as a laccase. The enzyme is interestingly tolerant to elevated

concentrations of hydrogen peroxide, and has high affinity towards common laccase substrates.

The potential of the produced laccase is explored in a series of applications with important

environmental implications. Indeed, the enzyme, in both free and immobilized forms, is able to

decolorize an azo and triphenylmethane dyes. Moreover, laccase from Galerina Sp. is presented as a

very good agent for the demethylation of hard wood Kraft lignin from eucalyptus as well as some

lignin model compounds. In this context, a fast and sensitive spectrophotometric method for

measuring the released methanol is adapted, presenting an alternative to gas chromatography.

Laccase mediated lignin modification, including demethylation, is known to make it more reactive

and prone to coupling. Therefore, this feature is further employed in the thesis to oxidize a range of

lignin model compounds and catalyze their coupling to a substituted aromatic amine, highlighting the

involvement of laccase in water and soil detoxification. Insights into the mechanism of coupling are

given, and the kinetics of the enzymatic oxidations are studied using calorimetry.

Based on the concept of lignin activation by laccase, another field of investigation is approached in

this work covering the laccase-aided production of formaldehyde-free wood bioadhesives. A variety

of polymeric materials (a synthetic polymer, a natural polysaccharide, and a protein) are reacted with

Kraft lignin in the presence of laccase and a redox mediator in order to form composites with adhesive

properties. The tensile and shearing strengths of the produced adhesives are evaluated. In addition,

sorption isotherms are employed in order to characterize some of those composites in terms of their

capacity to adsorb or release water vapour from their surface at different humidities. Results are

useful for the evaluation of surface properties. (Less)
Abstract
Laccase, the phenol oxidizing enzyme, was first described towards the end of the 19th century from the wound sap of the lacquer tree Rhus vernicifera. The enzyme has the widest distribution in nature among the multicopper oxidases. It catalyzes single electron transfer oxidation in the presence of molecular oxygen producing water as by-product. Based on these highly desired mild oxidising conditions and wide range of substrates, immense efforts have marked the last decades on search for new enzyme sources and potential laccases that are suitable for different applications.

In the present thesis, a litter degrading fungus from Galerina sp. is introduced as a laccase producer. The fungus was grown on different agricultural... (More)
Laccase, the phenol oxidizing enzyme, was first described towards the end of the 19th century from the wound sap of the lacquer tree Rhus vernicifera. The enzyme has the widest distribution in nature among the multicopper oxidases. It catalyzes single electron transfer oxidation in the presence of molecular oxygen producing water as by-product. Based on these highly desired mild oxidising conditions and wide range of substrates, immense efforts have marked the last decades on search for new enzyme sources and potential laccases that are suitable for different applications.

In the present thesis, a litter degrading fungus from Galerina sp. is introduced as a laccase producer. The fungus was grown on different agricultural residues in submerged and solid state fermentations to produce high amounts of laccase. The major laccase out of four isoforms produced by the fungus was purified to homogeneity and characterized. The physical and biochemical properties are found to be similar to those of other known laccases from different fungi. The enzyme is remarkably tolerant to elevated concentrations of hydrogen peroxide, and has high affinity towards common laccase substrates.

The potential of the laccase is explored for various applications with important environmental implications. Indeed, the enzyme, in both free and immobilized forms, was able to decolorize a diazo and a triphenylmethane dyes. Moreover, the Galerina sp. laccase was successfully used to demethylate hard wood Kraft lignin. Laccase mediated lignin modification is known to make it more reactive and prone to coupling. In order to understand the modifications taking place, the Galerina sp. laccase was employed to oxidize a range of lignin monomeric derivatives and facilitate their coupling to a substituted aromatic amine. The kinetics of the enzymatic oxidation was studied using calorimetry.

Lignin activation by laccase has also been applied for the production of formaldehyde-free wood bioadhesives. In other words, lignin, a natural adhesive in plants, after extraction and modification, ends up as a wood adhesive outside the plants. In this context, a variety of polymeric materials (a synthetic polymer, a natural polysaccharide, and a protein) were reacted with Kraft lignin in order to form composite adhesives. The tensile strength and water resistance of the adhesive formulations were evaluated. Changes in surface properties due to the modifications were also studied by determining water sorption isotherms. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • PhD Pekka, Maijala, Department of Food and Environmental Sciences, University of Helsinki, Finland
organization
publishing date
type
Thesis
publication status
published
subject
defense location
Lecture Hall B, Center for Chemistry and Chemical Engineering, Sölvegatan 39, Lund University Faculty of Engineering
defense date
2011-06-16 10:15
ISBN
978-91-89627-73-4
language
English
LU publication?
yes
id
f579664e-7004-4e30-a18e-883fbc6873a9 (old id 1968939)
date added to LUP
2011-05-25 08:08:53
date last changed
2016-09-19 08:45:16
@misc{f579664e-7004-4e30-a18e-883fbc6873a9,
  abstract     = {Laccase, the phenol oxidizing enzyme, was first described towards the end of the 19th century from the wound sap of the lacquer tree Rhus vernicifera. The enzyme has the widest distribution in nature among the multicopper oxidases. It catalyzes single electron transfer oxidation in the presence of molecular oxygen producing water as by-product. Based on these highly desired mild oxidising conditions and wide range of substrates, immense efforts have marked the last decades on search for new enzyme sources and potential laccases that are suitable for different applications. <br/><br>
 In the present thesis, a litter degrading fungus from Galerina sp. is introduced as a laccase producer. The fungus was grown on different agricultural residues in submerged and solid state fermentations to produce high amounts of laccase. The major laccase out of four isoforms produced by the fungus was purified to homogeneity and characterized. The physical and biochemical properties are found to be similar to those of other known laccases from different fungi. The enzyme is remarkably tolerant to elevated concentrations of hydrogen peroxide, and has high affinity towards common laccase substrates. <br/><br>
 The potential of the laccase is explored for various applications with important environmental implications. Indeed, the enzyme, in both free and immobilized forms, was able to decolorize a diazo and a triphenylmethane dyes. Moreover, the Galerina sp. laccase was successfully used to demethylate hard wood Kraft lignin. Laccase mediated lignin modification is known to make it more reactive and prone to coupling. In order to understand the modifications taking place, the Galerina sp. laccase was employed to oxidize a range of lignin monomeric derivatives and facilitate their coupling to a substituted aromatic amine. The kinetics of the enzymatic oxidation was studied using calorimetry.<br/><br>
 Lignin activation by laccase has also been applied for the production of formaldehyde-free wood bioadhesives. In other words, lignin, a natural adhesive in plants, after extraction and modification, ends up as a wood adhesive outside the plants. In this context, a variety of polymeric materials (a synthetic polymer, a natural polysaccharide, and a protein) were reacted with Kraft lignin in order to form composite adhesives. The tensile strength and water resistance of the adhesive formulations were evaluated. Changes in surface properties due to the modifications were also studied by determining water sorption isotherms.},
  author       = {Ibrahim, Victor},
  isbn         = {978-91-89627-73-4},
  language     = {eng},
  title        = {Laccase from a Litter Degrading Fungus: Evaluation for Environmental Applications and Modification of Lignin to a Bioadhesive},
  year         = {2011},
}