In vitro comparism of the extracellular secretion of inulosucrase enzyme in potential probiotic Escherichia coli 16 and BL-21

Abstract

Escherichia coli 16 has potential probiotic properties including antimicrobial activity due to extracellular secretion of colicins E1/1a1b. Inulosucrase (InuJ) enzyme catalyses the polymerization of a fructose moiety of sucrose leading to the formation of fructooligosaccharides. The present investigation compared the activity of InuJ enzymes cloned into pMAL-p2ΔlacI^Q a deletion vector and transformed into E. coli 16 and standard strain that is, E. coli BL21. Specific activities of InuJ enzyme were estimated in supernatant, periplasm and lysate. Specific activities of InuJ activity in cell lysate were similar in E. coli 16 and E. coli BL21 without induction of tac promoter with isopropyl thio-β-Dgalactoside (IPTG). InuJ activity is mainly present in the periplasm of E. coli BL21 whereas in E. coli 16, most of the activity is in the supernatant. Superantant of E. coli 16 strain also showed good antibacterial activity due to colicin E1/Ia1b. Colicin E1/1a1b transport system could allow extracellular secretion of InuJ proteins in probiotic E. coli 16.

Key words: Colicin, extracellular, E. coli, fructooligosaccharide, inulosucrase, prebiotic, probiotic.