Oxidative polymerisation of models for phenolic lignin end-groups by laccase

• The redox enzyme laccase can lead to cross-linking of lignin molecules by oxidising phenolic end groups to resonance-stabilised radicals that can undergo radical coupling to form covalent bonds. This property has potential for many technical applications. However, laccase treatment can also lead to degradation. Experiments were performed with two laccases of different oxidation potential and pH and temperature optima. The predominant reaction following laccase oxidation is the formation of 5-5' and 4-O-5' bonds. If the 5-position is blocked, other reactions occur, including coupling of the 1-position and oxidation of the a-position, which aggravates cross-linking of different lignin molecules. The product profile generated by the two laccases is somewhat different, mainly because of the different pH rather than differences in enzyme activity. Reaction mechanisms and the technical and biological significance of the results are discussed.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Pappers-, massa- och fiberteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Paper, Pulp and Fiber Technology (hsv//eng)

Nyckelord

biotechnology

laccase

lignin

lignin model compound

lignin

polymerisation

phenolic end group

reaction mechanism

flight mass-spectrometry

kraft pulp

mediator

delignification

degradation

quinones

polymers

oxidase

oxygen

ms

Cellulose and paper engineering

Cellulosa- och pappersteknik

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)