Enzymes catalyzing redox reactions (oxidoreductases) represent an environmentally-friendly alternative to harsh chemical reagents in industrial processes that include oxidative transformations for the production of chemicals and other value-added products with large markets in developed and emerging economies. Fungi and other micro-organisms provide the wider and more easily exploitable source for this type of enzymes. However, the penetration of microbial oxidoreductases in the above markets is still low despite the recent discovery of some of the most promising enzymes. Moreover, the use of enzymes as biocatalysts requires tuning their catalytic and operational properties, a type of genetic manipulation that is possible nowadays by the use of protein engineering tools. In the above scenario, the PEROXICATS project focuses first on the search for new peroxidases, one of the most interesting types of oxidoreductases due to their high redox-potential and unique peroxygenase activity recently described in some of them. The huge amount of genomic resources available nowadays, and to be generated during the course of the project, will be exploited in the search for new fungal peroxidase/peroxygenase genes. This will provide a collection of new enzymes to be evaluated in different oxidation reactions that could result in interesting products. On the other hand, some of the main issues presently limiting the industrial application of these enzymes will be addressed, namely their suicide inactivation by peroxide, low functional expression, and limited oxygen transfer potential. Moreover, the catalytic properties of the most interesting enzyme candidates will be modulated to adapt them to the industrial processes. In both cases, a combination of rational and non-rational design will be used, based on directed mutagenesis, and random mutagenesis together with high-throughput screening methods, respectively. In this way, a toolbox of novel and robust peroxidases/peroxygenases will be obtained with high industrial potential. The wide substrate specificity and catalytic plasticity of some peroxidases, which will be further improved within PEROXICATS, make them suitable, for example, to substitute harsh chemicals in the oxidation of recalcitrant compounds or other type of compounds for which a high-redox potential oxidant is required. Peroxygenases have also a great biotechnological potential since they can catalyze selective oxyfunctionalization reactions, among others, required in organic synthesis and difficult to achieve by conventional chemical tools. These characteristics make them of considerable interest in fine chemistry (e.g. substituting costly hydroxylation reactions currently used in the pharmaceutical sector) and bulk chemistry (e.g. for hydrocarbon oxyfunctionalization). More information in www.peroxicats.org.