Mutagenesis and screening for cellulase (endo-1,4-β-D-glucanase) deficient strains of the white-rot basidiomycete Trametes trogii Berk

We investigated the solid-state pre-treatment of wheat straw by a strain of the wood-rotting fungus Trametes trogii Berk in Trog. Glucose can be recovered from lignocellulose-based raw materials by a biodelignification process in which cellulose degradation is minimized and lignin degradation maximized. We have used two strategies to develop such a process: 1) analysis of the effect of growth conditions on the hydrolysis yield of residual cellulose after pre-treatment, and 2) the genetic improvement of the ligninolytic fungal-strain. The first approach was dealt with in a previous paper. Here, in this paper, we present the results obtained with the conventional genetics approach. When working with polynucleate microorganisms, it is essential to obtain cells with a single nucleus for mutagenesis. We have developed a routine method for obtaining basidiospores from T trogii solid cultures. We isolated basidiospores, irradiated them with UV light to generate mutations and screened the survivors for cellulase activity. We isolated 12 mutants from 140 000 isolates, three of which were still deficient in cellulase.