Abstract
Fructosyltransferases have been used in the industrial production of fructooligosaccharides (FOS). However, it is still not possible to explain the difference in FOS production based on the variations observed in the FOS synthesizing enzymes of A. niger. In the present study, a novel fructosyltransferase (FT-A) from A. niger TCCC41686 with high FOS synthesis ability was characterized. The FT-A gene was obtained and expressed in Pichia pastoris. A homology model of FT-A showed that the changes of residues identified outside the conserved domains were found to have an effect on its characteristics and its FOS-synthesis capacity. The optimal activity of the recombinant FT-A was observed at 50 °C and pH 6.0, and it was stable below 50 °C and over the range of pH 3.0-11.0. The K m and V max values of FT-A were 151.13 g L-1 and 6.55 g L-1 min-1, respectively. The production of FOS using the recombinant FT-A remained above 60% during 50-80 min of synthesis based on sucrose as substrate. The novel fructosyltransferase (FT-A) investigated in this study can potentially be applied for the efficient industrial production of FOS. The results also provide more valuable information for explaining the relationship between the structure and function of the FT-A.