The response surface optimization of exopolysaccharide produced by <i>Weissella confusa</i> XG-3 and its rheological property
Dan Zhao, Lina Liu, Jing Jiang, Shangxu Guo, Wenxiang Ping, Jingping Ge
Abstract
The response surface methodology (RSM) was used to optimize the exopolysaccharide (EPS) production by a lactic acid bacteria (LAB) Weissella confusa XG-3. Two-level factorial design screened three significantly influencing factors sucrose, initial pH and sodium acetate. Central composite design (CCD) predicted under the condition of sucrose 80.1 g L−1, initial pH 5.8 and sodium acetate 3.7 g L−1, the maximal EPS yield obtained a 2.9-fold increase, reaching 97.5 ± 1.1 g L−1. This maximal value was far exceeding EPS production by other W. confusa species strains reported so far. The results suggested that W. confusa XG-3 had a potential for large-scale EPS production. The rheological properties of XG-3 EPS was further investigated. It was a typical non-Newtonian fluid, exhibiting pseudo-plastic behavior. The EPS concentration and temperature exerted positive and negative impact on apparent viscosity, respectively. The XG-3 EPS maintained relatively higher viscosity at moderate pH (6–8). The intrinsic viscosity [η] was 409.7 (25 °C) and 201.7 (35 °C), which was relevant to temperature but irrelevant to EPS concentration. This EPS efficiently coagulated sucrose-supplemented milk in a concentration-dependent manner. These results indicated that XG-3 EPS had an applicable potential in food processing fields especially dairy products.