Properties of recombinant 4-α-glucanotransferase from Bifidobacterium longum subsp. longum JCM 1217 and its application

To determine the physiochemical properties of the 4-alpha-glucanotransferase from Bifidobacterium sp., the bllj_0114 gene encoding 4-alpha-glucanotransferase was cloned from Bifidobacterium longum subsp. longum JCM 1217 and expressed in Escherichia coli. The amino acid sequence alignment indicated that the recombinant protein, named BL-alpha GTase, belongs to the glycoside hydrolase (GH) family 77. BL-alpha GTase was purified using nickel-nitrilotriacetic acid affinity chromatography and characterized using various substrates. The enzyme catalyzed the disproportionation activity, which transfers a glucosyl unit from oligosaccharides to acceptor molecules, and had the highest activity at 40 degrees C and pH 6.0. In the presence of 5 mM metal ions, in particular Cu2+, Zn2+, and Fe2+, BL-alpha GTase activity was reduced. To determine whether BL-alpha GTase can be used to generate thermoreversible gels, potato starch was treated with BL-alpha GTase for various reaction times. The BL-alpha GTase-treated starches showed sol-gel reversibility and melted at 59.6-75.7 degrees C.