Production of high‐purity isomalto‐oligosaccharides syrup by the enzymatic conversion of transglucosidase and fermentation of yeast cells

Abstract

A method for the production of high-purity isomalto-oligosaccharides (IMO) involving the transglucosylation by transglucosidase and yeast fermentation was proposed. The starch of rice crumbs was enzymatically liquefied and saccharified, and then converted to low-purity IMO syrup by transglucosylation. The low-purity IMO produced either from rice crumbs or tapioca flour as the starch source could be effectively converted to high-purity IMO by yeast fermentation to remove the digestible sugars including glucose, maltose, and maltotriose. Both Saccharomyces carlsbergensis and Saccharomyces cerevisiae were able to ferment glucose in the IMO syrup. Cells of S. carlsbergensis harvested from the medium of malt juice were also able to ferment maltose and maltotriose. A combination of these two yeasts or S. carlsbergensis alone could be used to totally remove the digestible sugars in the IMO, coupled with the production of ethanol. The resultant high-purity IMO, including mainly isomaltose, panose, and isomaltotriose made up more than 98% w/w of the total sugars after a 3-day fermentation. When the low-purity IMO was produced from the starch of tapioca flour, 3-day fermentation under the same conditions resulted in IMO with purity lower than that from rice crumbs. For low-purity IMO from rice crumbs, fermentation with washed S. carlsbergensis cells harvested at log phase was the most effective. However, for the low-purity IMO from tapioca flour, incubation with S. cerevisiae for the first 24 h and then supplementing with an equal amount of S. carlsbergensis cells for further fermentation was the most effective approach for producing high-purity IMO.

Controlled germination to enhance the functional properties of rice

“…Transglucosylation by a-glucosidase might also take place during mashing [42]. aGlucosidase could catalyse both the hydrolysis of a-D-glucooligosaccharides and transfer the glucosyl group to 6-OH of glucose.…”

Industrial Enzyme Applications in Biorefineries for Starchy Materials

“…IMO is commercially one of the most important polysaccharide categories with an estimated market demand of about 200,000 t per year worldwide (van Dokkum et al 1999 ). The conventional method of producing IMO from starch involves a three-step enzymatic process, liquefaction using thermostable α-amylase, followed by saccharifi cation using pullulanase and beta-amylase to produce maltose, which in the third step is used as the substrate for the transglucosidase enzyme to produce IMO (Pan and Lee 2005 ). The transglucosidase catalyzes both hydrolytic and transfer reactions on incubation with α-D -gluco-oligosaccharides.…”

A high-throughput method for screening of Aspergillus niger mutants with high transglycosylation activity by detecting non-fermentable reducing sugar

“…Yeast has been used to remove digestible sugars including glucose, maltose and maltotriose in commercial IMO syrup production (Harder et al 1983;Pan and Lee 2005). S. cerevisiae strain GXJ-1 used in this study was isolated from the starter of alcohol fermentation and preserved in our laboratory.…”