Purification and characterization of dextransucrase from Weissella cibaria RBA12 and its application in in vitro synthesis of prebiotic oligosaccharides in mango and pineapple juices

•Dextransucrase-RBA12 displayed maximal activity at 40 °C and pH 5.4.•Mg2+ and Ca2+ ions enhanced the enzyme activity by 40% and 25%, respectively.•Using maltose IMOs, DP3-DP6 were produced and confirmed by ESI-TOF MS.•IMOs, DP3-DP5 were synthesized in situ in mango and pineapple juices using dextransucrase-RBA12.

Dextransucrase produced by Weissella cibaria RBA12 isolated from pummelo was purified by PEG-400 and PEG-1500 fractionation, followed by gel filtration. The enzyme purified by 0.25 mL/L PEG 400 gave specific activity 410 μkat/g with 25-fold purification. Purified dextransucrase gave a single, homogeneous protein of molecular size ∼180 kDa on analysis by SDS-PAGE. Purified dexransucrase was optimally active at 40 °C and pH 5.4. It gave maximum velocity (Vmax) and Michaelis constant (Km) of 488.3 μkat/g and 19.2 mmol/L, respectively. The enzyme was thermally stable up to 30 °C and highest pH stability at pH 5.5 for 1 h Mg2+ and Ca2+ ions enhanced the enzyme activity by 40% and 25%, respectively. The in-situ production of isomalto-oligosaccharide was carried out by dextransucrase using mango and pineapple juices. The native sugars (sucrose, glucose and fructose) present in both juices were confirmed by HPLC. The glucose and fructose present in juices acted as acceptor molecules. In both juices, isomalto-oligosaccharides from DP3 to DP5 along with isomaltose (DP2) and leucrose (DP2) were synthesized in situ by dextransucrase reaction utilizing the native sucrose. Sucrose content of the juices was eliminated resulting in its lower calorific value highlighting the potential of dextransucrase for production of functional foods.