Cost-effective and controllable synthesis of isomalto/malto-polysaccharides from β-cyclodextrin by combined action of cyclodextrinase and 4,6-α-glucanotransferase GtfB

Isomalto/malto-polysaccharides (IMMPs) derived from malto-oligosaccharides such as maltoheptaose (G7) are elongated non-branched gluco-oligosaccharides produced by 4,6-alpha-glucanotransferase (GtfB). However, G7 is expensive and cumbersome to produce commercially. In this study, a cost-effective enzymatic process for IMMPs synthesis is developed that utilizes the combined action of cyclodextrinase from Palaeococcus pacificus (PpCD) and GtfB-Delta N from Limosilactobacillus reuteri 121 to convert beta-cyclodextrin into IMMPs with a maximum yield (16.19 %, w/w). The purified IMMPs synthesized by simultaneous or sequential treatments, designated as IMMP-Sim and IMMP-Seq, possess relatively high contents of alpha-(1 -> 6) glucosidic linkages. By controlling the release of G7 and smaller malto-oligosaccharides by PpCD, IMMP-Seq was obtained of DP varying from 12.9 to 29.5. Enzymatic fingerprinting revealed different linkage-type distribution of alpha-(1 -> 6) linked segments with alpha-(1 -> 4) segments embedded at the reducing end and middle part. The proportion of alpha-(1 -> 6) segments containing the non-reducing end was 56.76 % for IMMP-Sim but 28.98 % for IMMP-Seq. Addition of G3 or G4 as specific acceptors resulted in IMMPs exhibiting low polydispersity. This procedure can be applied as a novel bioprocess that does not require costy high-purity malto-oligosaccharides and with control of the average DP of IMMPs by adjusting the substrate composition.

Automated summary

A cost-effective enzymatic process for the synthesis of Isomalto/malto-polysaccharides (IMMPs) was developed using cyclodextrinase and GtfB-Delta N to convert beta-cyclodextrin into IMMPs. The yield reached 16.19% (w/w) and the average DP of IMMPs could be controlled by adjusting the substrate composition.