茯苓多糖组分对复合乳酸菌的冻干保护作用及机理

Freeze-drying protective effect and mechanism of component from Poria cocos polysaccharide on compound lactic acid bacteria

为探究茯苓多糖(Poria cocos polysaccharide,PCP)组分对复合乳酸菌冷冻干燥的保护效果,制备茯苓多糖纯化组分,并对其结构进行表征,研究其对复合乳酸菌冷冻干燥的保护效果及作用机理。结果表明,茯苓多糖经分离纯化后得到总糖含量为(96.21±0.39)%的PCP-1,PCP-1的重均分子质量为11732 Da;主要由葡萄糖和葡萄糖醛酸组成,其摩尔比为0.989∶0.011;PCP-1中存在羟基,同时含有α-糖苷键和β-糖苷键。在基础保护剂中添加PCP-1相较于添加PCP使复合乳酸菌的冻干存活率增加了11.29%。通过扫描电镜观察到添加PCP-1的乳酸菌粉表面更加致密;添加PCP-1后复合乳酸菌的Na^(+)-K^(+)-ATP酶和乳酸脱氢酶的活力比起添加PCP得到显著增强,分别增加了0.66、1.46 U/mg prot;经过碘化丙啶和二乙酸荧光素双重染色后观察到添加PCP-1的复合乳酸菌的细胞膜完整性得到更好的保持。PCP-1可能是通过羟基的存在形成氢键来降低复合乳酸菌的冻干损伤,提高复合乳酸菌的冻干存活率。

To explore the protective effect of component from Poria cocos polysaccharide(PCP)on freeze-drying of compound lactic acid bacteria,purified component from Poria cocos polysaccharide was prepared successfully and its structure was characterized,studying its protective effect and mechanism on freeze-drying of compound lactic acid bacteria.Results showed that PCP-1 with total sugar content of(96.21±0.39)%was obtained after isolation and purification,and the weight average molecular weight of PCP-1 was 11732 Da.PCP-1 is mainly composed of glucose and glucuronic acid,with the molar ratio of 0.989∶0.011.Moreover,there are hydroxyl groups and bothαandβglycosidic bonds in PCP-1.Adding PCP-1 into the basic protective agent increased the freeze-dried survival rate of compound lactic acid bacteria by 11.29%when compared with PCP.The surface of lactic acid bacteria powder with PCP-1 was denser by observed with scanning electron microscope.Furthermore,the activities of Na^(+)-K^(+)-ATPase and lactate dehydrogenase of compound lactic acid bacteria were significantly enhanced by adding PCP-1 to the basic protective agent,which increased by 0.66 U/mg prot and 1.46 U/mg prot,respectively.The cell membrane integrity of the compound lactic acid bacteria added with PCP-1 was better maintained after double staining with propidium iodide and fluorescein diacetate.In conclusion,PCP-1 may reduce the freeze-drying damage of compound lactic acid bacteria by forming hydrogen bonds through the existence of hydroxyl groups,and improve the freeze-drying survival rate of compound lactic acid bacteria.