Standard protocols were followed for DNA manipulation [26] with enzymes for restriction digests and ligations sourced from Roche Applied Science (Germany). Where applicable, DNA was eluted from agarose gels with the Zymoclean™ Gel Recovery Kit (Zymo Research). The glaA gene was subcloned as an EcoRI-XhoI fragment and the amyA gene as an EcoRI fragment into the corresponding sites of plasmid yBBH1, yielding plasmids yBBH1-AmyA and yBBH1-GlaA, respectively (Figure 1). The ENO1P-GlaA-ENO1T cassette was excised from yBBH1-GlaA as a BamHI-BglII fragment and cloned into the BglII site on pBBH1-AmyA, generating pBBH1-AmyA-GlaA (Figure 1).
The host strains, S. cerevisiae Y294 and S. cerevisiae Mnuα1, were transformed with the recombinant plasmids using electroporation [43] with subsequent selection on SC-URA plates. The presence of the respective amylase genes was verified by PCR amplification with gene-specific primers (Table 3).