초록
Isomalto-oligosaccharides (IMOs), one of the emerging prebiotics, were synthesized by transglycosylation activity of the cell bound α-glucosidase of a novel strain of Microbacterium sp. using maltose as a glycosyl donor. Parameters affecting yield were optimized and a yield of 85 g/l was obtained at 40% (w/v) initial substrate concentration after 24 h using whole cells (~25 IU α-glucosidase activity). A mixture of isomaltotriose, isomaltotetraose, isomaltopentaose and isomaltohexaose were obtained as determined by electrospray ionization mass spectrometry. Addition of 0.5 M LiCl to the reaction mixture lead to a further 15% increase in the yield. The synthesized IMOs were purified for structure analysis by preparative thin layer chromatography and structures elucidated by <SUP>1</SUP>H and <SUP>13</SUP>C NMR. The chemical shift values of <SUP>13</SUP>C NMR clearly confirmed that the products formed were isomaltotriose and isomaltotetraose (α-1,6 linked). The reactions were scaled up in a column to 100 ml level using immobilized cells. An increase in productivity by 4.2 times was achieved in this system with a conversion efficiency of 24%.