5-68: Yeast surface display of cellulolytic and xylanolytic enzymes

Direct and efficient production of platform chemicals from cellulosic and hemicellulosic materials would be an economically very interesting process. Itaconic acid, an unsaturated dicarboxylic acid, is such a platform chemical which subsequently can be converted into a number of high-value bio-based chemicals and also to liquid fuel.

For the production of itaconic acid from cellulosic and hemicellulosic materials, we constructed yeast strains by genetically displaying cellulolytic or xylanolytic enzymes on the cell surface of Saccharomyces cerevisiae. These strains can be used in cofermentations with the basidiomycetous fungus Ustilago maydis, a potential itaconic acid producer. We used a cell surface engineering system based on a-agglutinin to construct S. cerevisiae strains displaying on the cell surface different types of cellulose- and xylan-degrading enzymes, namely xylanase, cellobiohydrolase I or endo-b-glucanase I or II from Trichoderma reesei, b-xylosidase from Aspergillus terreus or xylanase from U. maydis. The expression of the genes was verified by immunofluorescence, and enzymatic activities were measured with suitable methods.