Altered Rheological Properties of Insoluble α-Glucan, Synthesized by Mutant Glucansucrase U13M1

Abstract

Lactic acid bacteria from the Leuconostoc, Lactobacillus, and Streptococcus genera produce en¬zymes from the glucoside hydrolase family 70 (GH70) that synthesize α-D-glucans with various types of linkages and degrees of branching. These polymers with novel physico-chemical properties are an object of great interest for expanding application in the food, pharmaceutical, and cosmetic industries. Using site-directed mutagenesis, a mutant variant of glucansucrase URE 13-300 was obtained. The enzyme ex¬pression of the modified enzyme was optimized and the rheological properties of both types of glucans were evaluated. The modified insoluble glucan, synthesized by mutant glucansucrase U13M1 exhibited significantly higher apparent viscosity at 8°C – 3550 mPa.s at a shear rate of 0.2 s-1 than the original glucan. Higher temperatures up to 80°C had a moderate influence on the viscosity as well. The presented findings are a good precondition for further exploration of modified insoluble glucans for industrial application.