The availability of a rapidly increasing number of genome sequences of basidiomycete fungi has resulted in a strongly growing interest in basidiomycete genes and enzymes, in particularly those related to plant biomass degradation. The arsenal of enzymes produced by basidiomycete fungi differs markedly from those produced by ascomycete fungi, and the properties of the enzymes are also different. Most basidiomycetes do not have efficient transformation systems and large scale enzyme production in basidiomycetes is challenging. Therefore, heterologous production in ascomycete hosts is often the approach of choice, but there are still many challenges in producing these enzymes. Factors hampering heterologous expression of basidiomycete genes in ascomycetes include differences in the gene content such as in codon usage bias, and intron structure and size. In addition, basidiomycete enzymes are often considered foreign by the ascomycete production systems and therefore targets for their proteolytic systems, reducing the production yields.

In this chapter we provide the state of the art of expression of basidiomycete genes involved in plant biomass degradation and the production of the corresponding enzymes. Both homologous and heterologous expression is addressed and an overview of successful studies including the production yield is presented.