The α-glucosidase gene of Aspergillus niger was expressed in Saccharomyces cerevisiae under control of a galactose-inducible promoter. Recombinant yeast cells expressing the aglA gene produced extracellular α-glucosidase activity. With maltose as the substrate, panose is the main transglycosylation product after 8 h of incubation, whereas isomaltose is predominant after 24 h. Isomaltose also becomes predominant at shorter times if a mixture of maltose and glucose is used instead of maltose. To facilitate IMO production, we have designed a procedure by which yeast cells can be used directly as the catalytic agent. For this purpose, we expressed in S. cerevisiae gene constructs in which the aglA gene is fused to glycosylphosphatidylinositol anchor sequences, from the yeast SED1 gene, that determine the covalent binding of the hybrid protein to the cell membrane. The resulting hybrid enzymes were stably attached to the cell surface. The cells from cultures of recombinant yeast strains expressing aglA-SED1 constructions can be used to produce IMOs in successive batches.
Reference: M. Casa-Villegas, J. Marín-Navarro, J. Polaina. "Synthesis of isomaltooligosaccharides by Saccharomyces cerevisiae cells expressing Aspergillus niger alpha-glucosidases". ACS Omega 2, 11, 8062-8068 (2017). doi:10.1021/acsomega.7b01189