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Oral
Presentation 6-02 The
Role of Oxidative Enzymatic Treatments on Enzymatic Hydrolysis of
Lignocellulose Hetti
Palonen and Liisa Viikari VTT Biotechnology P.O.Box 1500 FIN-02044 VTT, Finland Telephone: +358-9-456 7176; Fax: +358-9-455 2103; E-mail: Hetti.Palonen@vtt.fi Most pretreatment methods for biomass
conversions aim at solubilization of hemicellulose and/or lignin. Both these components have been shown to
have an effect on the hydrolysis of lignocellulose. Generally, high hydrolyzability has been obtained with
delignified fibres. Lignin and
cellulose are partially interlinked and lignin may physically restrict the
accessibility of cellulose. Lignin can
also adsorb cellulase enzymes, lowering the effective enzyme concentration in
hydrolysis. Laccases together with
small molecular weight mediators are capable of oxidation of phenolic
compounds, thus altering the structure of lignin polymer. In this work, laccase treatment was combined
with enzymatic hydrolysis of steam-pretreated softwood in order to improve the
conversion of cellulose. The solid
substrates were saccharified with commercial cellulases in the presence of NHA
or NHA-DiAc mediators and laccase preparations from Trametes hirsuta. The level of cellulose conversion, dissolved
lignin and residual cellulase activities were determined. The amounts of NHA
and laccase were optimised in order to avoid inhibitory effects on the
cellulase activity. The simultaneous enzymatic treatments were also compared
with separate chemical delignification. The removal of lignin was shown to
increase the enzymatic hydrolysis of cellulose.
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