Wheat Starch with Low Retrogradation Properties Produced by Modification of the GtfB Enzyme 4,6-α-Glucanotransferase from Streptococcus thermophilus

• DOI: 10.1021/acs.jafc.8b00550
• Publication Date: 2018-03-27T09:40:50Z
• Authors: Xiaolei Li; Teng Fei; Yong Wang; Yakun Zhao; Yutian Pan; Dan Li
• Keywords: Retrogradation (starch)

A GtfB enzyme 4,6-α-glucanotransferase from Streptococcus thermophilus lacking 761 N-terminal amino acids was heterologously expressed in Escherichia coli. Purified S. showed transglycosylation activities toward starch, resulting branch points of (α1→6)-glycosidic linkages plus linear chains (α1→4)-glycosidic linkages. After wheat starch modified at a rate 0.1 g/mL by 1-4 U/g pH 6.0 and 40 °C for 1 h, the weight-averaged molecular weight decreased 1.70 × 107 g/mol to 1.21 106 3.41 g/mol, amylose content 22.07 16.34-17.11%, that amylopectin long-branch 26.4 10.25-15.64% ( P < 0.05). GtfB-modified starches were gelatinized stored 4 1-2 weeks, their endothermic enthalpies significantly lower than control sample 0.05), indicating low retrogradation rates.