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

Abstract

The EXG1 gene encoding the main Saccharomyces cerevisiae exo- β-1,3-glucanase was cloned and over-expressed in yeast. The Bacillus subtilis endo-1,3-1,4- β-glucanase gene ( beg1) 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-MFα1 S-beg1-ADH2 T and ADH2 P-MFα1 S-end1-ADH2 T , designated BEG1 and END1, respectively, were expressed separately and jointly with EXG1 in S. cerevisiae. The construction of fur1 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 END1 enhanced glucan degradation by S. cerevisiae.