Unveiling four levansucrase enzymes: Insights into catalytic properties, kinetics, and end-product profiles

Abstract

The biocatalytic approach based on Levansucrase (LS)-catalyzed transfructosylation reaction is of particular interest for the synthesis of well-defined FOSs and β-(2−6)-levan. The present study aims to characterize the catalytic properties, kinetics, and end-product profiles of new LSs derived from Novosphingobium aromaticivorans, Vibrio natriegens, Gluconobacter oxydans, and Burkholderia graminis. The optimal conditions for achieving the highest ratio of transfructosylation to hydrolysis was achieved were identified as follows: N. aromaticivorans LS1 (T 45 °C, pH 6, Ea 33.88 kJ/mol), V. natriegens LS2 (T= 45 °C, pH 5, Ea= 12.74 kJ/mol), B. graminis LS3 (T= 35 °C, pH 7, Ea= 20.72 kJ/mol), and G. oxydans LS4 (T= 30 °C, pH 5, Ea= 51.85 kJ/mol). The kinetic study revealed that LS from G. oxydans LS4 had the highest catalytic efficiency for the transfructosylation of sucrose (112.96 s−1M−1) and raffinose (1142.7 s−1 M−1) than their hydrolysis (39.15 and 16.5 s−1M−1 respectively). Our results highlighted the end-product profile of each LS using sucrose and raffinose as donor substrates. V. natriegens LS2 and B. graminis LS3-catalyzed sucrose bioconversion reaction resulted in the synthesis of more diverse FOSs. When compared to FOSs, all LSs catalyzing sucrose and raffinose bioconversion produced high yields of oligolevans/levans.