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.

摘要

响应面方法（RSM）用于优化乳酸菌（LAB）Weissella confusa XG-3的胞外多糖（EPS）产生。两级因子设计筛选了三个显着影响因素的蔗糖，初始pH和乙酸钠。在蔗糖80.1 g L ^-1，初始pH 5.8和乙酸钠3.7 g L ^-1的条件下预测的中央复合设计（CCD），EPS的最高产量增加了2.9倍，达到97.5±1.1 g L ^-1。该最大值远远超过迄今报道的其他W. confusa物种菌株的EPS产量。结果表明W. confusaXG-3具有大规模生产EPS的潜力。进一步研究了XG-3 EPS的流变特性。它是典型的非牛顿流体，表现出假塑性行为。EPS浓度和温度分别对表观粘度产生正面和负面影响。XG-3 EPS在中等pH值（6-8）下保持相对较高的粘度。特性粘度[ η ]为409.7（25℃）和201.7（35℃），这与温度有关但与EPS浓度无关。该EPS以浓度依赖性方式有效地凝结了补充蔗糖的牛奶。这些结果表明，XG-3 EPS在食品加工领域，尤其是乳制品中具有可应用的潜力。