Abstract: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.
