植物乳杆菌K25发酵产胞外多糖的影响因素及其应用

Factors Affecting of Lactobacillus plantarum K25 Fermentation to Produce Exopolysaccharide and Its Application

植物乳杆菌胞外多糖(extracellular polysaccharide,EPS)可赋予发酵乳制品独特的质构和风味,还具有增强免疫力、抗肿瘤和调节肠道菌群平衡等生物活性,在食品和医药领域具有良好的应用前景。但是,植物乳杆菌EPS的产量偏低,而影响其产量的因素具有菌株特异性,有关添加植物乳杆菌EPS对产品稳定性影响的研究也较少。采用单因素实验和响应面法确定了植物乳杆菌K25产EPS的优化培养基组成:每升含胰蛋白胨10 g、酵母浸粉5 g、葡萄糖20 g、磷酸氢二钾2.0 g、无水乙酸钠5.0 g、柠檬酸钠5.0 g、硫酸镁0.2 g、硫酸锰0.05 g和吐温80 1.0 mL。优化的发酵条件:发酵温度30℃、发酵时长24 h和培养基初p H值6.5。在此条件下EPS产量为250.21 mg/L。流变学研究表明,该EPS水溶液的黏度具有随着浓度和剪切速率升高而升高,以及剪切变稠的特性。扫描电镜观察发现,该EPS具有长方形块状微观结构,有利于稳定溶液的质构并保持水分。将该EPS加入到酸性乳饮料中,进一步验证了其具有良好的保水特性,表明植物乳杆菌K25产生的EPS可以作为一种具有潜在应用价值的新型食品稳定剂。

The extracellular polysaccharide（ EPS） from Lactobacillus plantarum plays important roles in the special texture and flavor of fermented dairy products. These EPSs possess biological activities such as immunomodulation,antitumor and regulating the balance of intestinal flora and so on,which can be used in food and medicine fields. However,the yield of Lactobacillus plantarum EPS is relatively low,factors affecting the EPS production are strain specific,and the influence of Lactobacillus plantarum EPS on the stability of the products is still rarely studied. The optimal fermentation conditions obtained by single factor experiments and response surface analysis were as follows： peptone 10 g/L,yeast extract powder5 g/L,glucose 20 g/L,potassium hydrogen phosphate 2. 0 g/L,anhydrous sodium acetate 5. 0 g/L,sodium citrate 5. 0 g/L,magnesium sulfate 0. 2 g/L,manganese sulfate 0. 05 g/L,twain 80 1. 0 mL/L,fermentation temperature 30 ℃,fermentation time 24 h,and initial p H of culture medium of 6. 5. The maximal production of EPS was 250. 21 mg/L under the above conditions. The results of rheological characteristics studies indicated that the EPS aqueous solution exhibited the increased viscosity as the concentration of the EPS and the share rate increased,and shear thickening properties. The scanning electron microscopy verified the cuboid microstructure of the EPS molecules,facilitating stabilization of the texture and water retention in solution. Application of this EPS for preparation of acid milk beverage showed that the use of the EPS could improve stability of the beverage,indicating that the EPS from Lactobacillus plantarum K25 can be potentially used as a novel food stabilizer.