Characterization of a maltononaose-producing amylopullulanase from Bacillus aryabhattai W310

The recombinated amylopullulanase of PulW310B, pullulanase from Bacillus aryabhattai W310, was characterized. Sequence analysis of PulW310B showed that PulW310B has type I pullulanase structures including its typical region and the conserved regions of glycoside hydrolase family 13. Moreover, PulW310B was predicted to has typical domains of pullulanase and SSF51445 belonging to tansglycosidase. While the substrate specificity of PulW310B presented that it is not a type I pullulanase. PulW310B could hydrolyze pullulan into maltotriose, maltohexaose, and maltononaose as main products with the proportions of 73.6 %, 16.7 %, and 6.7 %, which indicated that PulW310B has a certain potential on maltooligosaccharides production due to its 4-α-transglycosylation activity that was consistent with its domain analysis. Based on substrate specificity and hydrolytic properties, PulW310B is an amylopullulanase. This is the first report of maltononaose producing activity of amylopullulanase, which will be very useful in food industry. Moreover, PulW310B is a moderate pullulanase with optimal temperature of 40 °C and pH of 7.0. 50 % of the maximum activity was retained at room temperature (25 °C), which indicated that it is an environmentally friendly enzyme in maltooligosaccharides production.