银耳多糖对冻干植物乳杆菌细胞膜及糖代谢酶的保护作用

为了探索银耳多糖作为益生菌冻干保护剂的潜在应用，该研究以植物乳杆菌为试验菌，通过测定植物乳杆菌冻干前后的活菌数、细胞膜性质以及糖代谢酶活力的变化，评价了银耳多糖复合酪蛋白酸钠对植物乳杆菌的冻干保护效果。结果表明：当银耳多糖与酪蛋白酸钠的复合比例为3:1时，菌的最大存活率达到55.39%，此时细胞内钙离子荧光强度显著降低，为29.98；DPH的荧光强度最低，为4.91；细胞内乳酸脱氢酶、钠钾ATP酶与钙镁ATP酶的活力最大，分别为0.32 U/mL、121.61 U/g与45.64 U/g。银耳多糖使膜受损的菌百分比从98.35%最大降低至37.90%。但冻干前后己糖激酶和丙酮酸激酶的活力无显著性变化。红外扫描结果表明银耳多糖与酪蛋白酸钠之间存在非共价相互作用；此外，银耳多糖的保护使菌粉表面的孔隙率降低，酪蛋白酸钠的复合则增加了菌粉的致密性。因此，银耳多糖在冷冻干燥过程中对植物乳杆菌细胞膜受到的损伤具有显著的抑制作用，对植物乳杆菌的乳酸脱氢酶、钠钾ATP酶及钙镁ATP酶具有明显的保护作用。

Protective Effects of Polysaccharides Extracted from Tremella on Cell Membrane and Sugar Metabolism Enzymes of Freeze-dried Lactobacillus plantarum

To explore the potential effects of polysaccharides extracted from tremella as a probiotic freeze-drying protectant, experiments were conducted using Lactobacillus plantarum in this study. The protective effects of polysaccharides extracted from tremella combined with sodium caseinate upon freeze-drying Lactobacillus plantarum were evaluated through assessing the viable bacterial counts, properties of the cell membrane, and activities of the sugar metabolism enzymes before and after freeze-drying. As a result, the maximum survival rate of the bacteria reached up to 55.39% when the ratio of polysaccharides extracted from tremella to sodium caseinate was 3:1. At the same time, the intracellular Ca2+ fluorescence intensity was found to be significantly reduced to 29.98, whereas the fluorescence intensity of DPH was as low as 4.91. The activities of lactate dehydrogenase, Na+/K+-ATPase, and Ca2+/Mg2+-ATPase were the highest, corresponding to 0.32 U/mL, 121.61 U/g and 45.64 U/g, respectively. The percentage of bacteria with damaged cell membrane reduced from 98.35% to 37.90%. However, there was no significant change observed in the activities of hexokinase and pyruvate kinase before and after freeze-drying. Infrared scans revealed that there were non-covalent interactions between polysaccharides extracted from tremella and sodium caseinate. Additionally, polysaccharides extracted from tremella reduced the surface porosity of the bacterial powder, while sodium caseinate increased its density. Therefore, polysaccharides extracted from tremella exerted a significant inhibitory effect on the damage of Lactobacillus plantarum cell membrane during the freeze-drying process, and they have an evident protective effect on the activities of lactate dehydrogenase, Na+/K+-ATPase and Ca2+/Mg2+-ATPase of Lactobacillus plantarum.