REVIEW Thermotolerant and thermostable laccases Kristiina Hilde ´n Æ Terhi K. Hakala Æ Taina Lundell Received: 17 February 2009 / Revised: 16 March 2009 / Accepted: 19 March 2009 / Published online: 10 April 2009 Ó Springer Science+Business Media B.V. 2009 Abstract Laccases are phenol-oxidizing, usually four-copper containing metalloenzymes. For industrial and biotechnological purposes, laccases were among the first fungal oxidoreductases providing larger-scale applications such as removal of polyphenols in wine and beverages, conversion of toxic compounds and textile dyes in waste waters, and in bleaching and removal of lignin from wood and non-wood fibres. In order to facilitate novel and more efficient bio-catalytic process applications, there is a need for laccases with improved biochemical properties, such as thermosta- bility and thermotolerance. This review gives a current overview on the sources and characteristics of such laccases, with particular emphasis on the fungal enzymes. Keywords Laccase Á Thermotolerance Á Thermostability Á Multicopper oxidase Á Fungi Á Microbial enzymes Abbreviations ABTS, 2 2-Azinobis(3-ethylbenz-thiazoline-6- sulfonate) 2,6-DMP 2,6-Dimethoxyphenol GUA Guaiacol (2-methoxyphenol) MCO Multicopper oxidase SGZ Syringaldazine (4-hydroxy-3,5- dimethoxybenzaldehyde azine) Introduction Applications utilizing microbial enzymes as biocata- lysts at the industrial scale are examples of so-called white biotechnology or green (sustainable) chemistry, which is recognized at the European level as one of the main sections for development in a biobased economy (http://www.bio-economy.net/). Due to harsh indus- trial process conditions that may include high tem- perature and/or pressure, high salt concentrations, acidic or alkaline pH, oxidative conditions, high shear forces or short delays, resistant enzymes are required. In addition there is a current need for enzymes with new catalytic properties for potential innovations and breakthroughs in industrial biotechnology. One of the general prerequisites for an enzyme to be applicable in industrial processes is thermotoler- ance (transient ability to maintain catalytic activity at elevated temperatures) or thermostability (ability to resist irreversible inactivation at high temperatures K. Hilde ´n Á T. Lundell Department of Applied Chemistry and Microbiology, Viikki Biocenter, University of Helsinki, Helsinki, Finland T. K. Hakala KCL, Espoo, Finland K. Hilde ´n (&) School of Biology, University of Nottingham, University Park, Nottingham NG7 2RD, UK e-mail: kristiina.s.hilden@helsinki.fi 123 Biotechnol Lett (2009) 31:1117–1128 DOI 10.1007/s10529-009-9998-0