Production and characterization of dextran and prebiotic isomalto-oligosaccharides from Weissella cibaria RBA12 isolated from Pummelo (Citrus maxima) for functional food applications

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Dextran producing lactic acid bacteria was isolated from the pulp of pummelo (Citrus maxima) and was phenotypically and biochemically characterized. Its was identified to be Weissella cibaria with the strain name given as RBA12 by 16S rRNA gene sequence analysis. The production conditions of enzyme dextransucrase was optimized from Weissella cibaria RBA12 and the enzyme was purified and characterized for the synthesis of isomalto-oligosaccharides. The production of dextran by Weissella cibaria RBA12 was optimized and the dextran production was scaled up to 2.5 L in batch fermentation followed by studies in dextran production in fed-batch fermentation. The dextran produced by Weissella cibaria RBA12 was also structurally and physico-chemically characterized. The functional food applications of the synthesized isomalto-oligosaccharides (IMO) and dextran were explored. The IMOs were purified by Bio-Gel P-2 chromatography and characterized by HPLC-RI and ESI-TOF MS analyses. The prebiotic IMOs and di-saccharides were produced by dextransucrase acceptor reaction using mango and pineapple juices utilizing their native sugars which acted as acceptors. The in vitro studies using simulated gastric juices, α-amylase and intestinal fluid were carried out on dextran for characterizing its prebiotic potential. The in situ production of dextran by Weissella cibaria RBA12 in whole wheat flour, wheat bran and rye bran was carried out in order to assess its application in the sourdough fermentation.
Supervisor: Arun Goyal