Over-expression of the Saccharomyces cerevisiae exo-β-1,3-glucanase gene together with the Bacillus subtilis endo-β-1,3-1,4-glucanase gene and the Butyrivibrio fibrisolvens endo-β-1,4-glucanase gene in yeast

The EXGI gene encoding the main Saccharomyces cerevisiae exo-β-1,3- glucanase was cloned and over-expressed in yeast. The Bacillus subtilis endo- 13-1,4-β-glucanase gene (beg 1) and the Butyrivibrio fibrisolvens endo-β- 1,4-glucanase gene (end1) were fused to the secretion signal sequence of the yeast mating pheromone α-factor (MFα1(S)) and inserted between the yeast alcohol dehydrogenase II gene promoter (ADH2(p)) and terminator (ADH2(T)). Constructs ADH2(p)MFα(s)-beg 1-ADH2(T) and ADH2(p)-MFα1(s)·end1-ADH2{T), designated BEGI and ENDI, respectively, were expressed separately and jointly with EXGI in S. cerevisiae. The construction of fur 1 ura3 S. cerevisiae strains allowed for the autoselection of these multicopy URA3-based plasmids in rich medium. Enzyme assays confirmed that co-expression of EXG1. BEG1 and ENDI enhanced glucan degradation by S. cerevisiae.