Surface display of novel transglycosylating α-glucosidase from Aspergillus neoniger on Pichia pastoris for synthesis of isomaltooligosaccharides

In the present study, α-glucosidase gene of Aspergillus neoniger, agdA, was fused with glycosylphosphatidylinositol (GPI)-anchored glycoprotein gene of Pichia pastoris, GCW61 at its C-terminus for functional expression in Pichia pastoris X-33. The expression of this chimeric gene was induced using methanol, and the protein was displayed on the surface of X-33 strain with cell pellet activity of 4.65 U/gDCW. The surface display of recombinant α-glucosidase was confirmed using immunofluorescence microscopy and flow cytometry. The strain displaying α-glucosidase protein was also cultivated in bioreactor using fed-batch cultivation to obtain a maximum activity of 0.158 U/gDCW and with cell density of 45.35 gDCW/L. These cells were later used as whole-cell biocatalysts (20 g wet cell weight/L) for production of isomaltooligosaccharides (IMOs) using 250 g/L of maltose as substrate. The IMO mixture contains isomaltose, panose, maltotetraose, isomaltotriose and three other higher DP oligosaccharides with a net yield of 0.4 g/g maltose. Amongst these, the panose yield was observed to be highest (0.25 g panose/ g maltose). Here we establish that the surface display of novel transglycosylating α-glucosidase on Pichia pastoris using GCW61p as an anchor protein can be used as whole-cell biocatalysts for synthesis of isomaltooligosaccharides. [Display omitted] •Transglycosylating α-glucosidase from A. neoniger was displayed on Pichia pastoris.•Surface displayed enzyme confirmed using microscopy and flow cytometry.•High cell density cultivation established for display of protein only on the cell surface.•Surface displayed cells were demonstrated for isomaltooligosaccharides production.