Novel thermotolerant laccases produced by the white-rot fungus <Emphasis Type="Italic">Physisporinus rivulosus</Emphasis> |
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Authors: | Kristiina Hildén Terhi K Hakala Pekka Maijala Taina K Lundell Annele Hatakka |
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Institution: | (1) Department of Applied Chemistry and Microbiology, Viikki Biocenter, University of Helsinki, Helsinki, Finland;(2) Present address: KCL Science and Consulting, Espoo, Finland;(3) Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 56, Biocenter 1, Helsinki, 00014, Finland |
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Abstract: | The white-rot basidiomycete Physisporinus rivulosus strain T241i is highly selective for degradation of softwood lignin, which makes this fungus suitable for biopulping. In
order to promote laccase production, P. rivulosus was cultivated in nutrient-nitrogen sufficient liquid media containing either charcoal or spruce sawdust as supplements.
Two laccases with distinct pI values, Lac-3.5 and Lac-4.8, were purified from peptone-spruce sawdust-charcoal cultures of P. rivulosus. Both laccases showed thermal stability at up to 60°C. Lac-4.8 was thermally activated at 50°C. Surprisingly, both laccases
displayed atypically low pH optima (pH 3.0–3.5) in oxidation of the commonly used laccase substrates syringaldazine (4-hydroxy-3,5-dimethoxybenzaldehyde
azine), 2,6-dimethoxyphenol and guaiacol (2-methoxyphenol). Steady-state kinetic measurements pointed to unusually low affinity
to guaiacol at low pH, whereas the kinetic constants for the methoxyphenols and ABTS were within the ranges reported for other
fungal laccases. The combination of thermotolerance with low pH optima for methoxylated phenol substrates suggests that the
two P. rivulosus T241i laccases possess potential for use in biotechnological applications. |
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Keywords: | Laccase White-rot fungi Physisporinus rivulosus Thermostability Thermal activation Lignin degradation |
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