Extraction And Purification Of Lactic Acid Bacteria Exopolysaccharides And Immune Activity

Exopolysaccharide (EPS), one kind of carbohydrates, is secreted by lactic acid bacteria during its growth metabolism. A summary of exopolysaccharide was showed in this paper, reflecting in its chemical characteristics, physiological function, application and the factors, which affected its yield as well. Besides, the researches on EPS production from Streptococeas thermophihos and Lactobacillus bulagaricus, capable of secreting exopolysaccharides, are conducted in production condition, extraction, purification and its immunological activities.The production conditions of EPS were selected during the process of producing yoghurt. It showed that there is the highest yield of EPS when seed volume is 2%, fermentation temperature reached to 38°C, fermentation lasted for 2.5 h and lower acidity presented at the end of fermentation. In the meantime, the effects of improvement of culture medium by adding the juice of apple, tomato, strawberry and grape on the yield of EPS are studied. It indicated that all the four juices are not only the growth-promoting substances for lactic acid bacteria, but also the yield-raising factors for EPS.There was a deproteinization procedure during the process of EPS from yoghurt. The deproteinization using Sevag method twice after enzymolysis resulted in the purified EPS. This procedure could increase the extraction rate of EPS and decreased the use of organic solvent.EPS was extracted from the cultures of Streptococeas thermophihos and Lactobacillus bulagaricus grown in MRS medium. The purification of EPS was carried out.The immunological activity of EPS was studied by using mouse inbred lines as experimental material. This substance from yoghurt did not affect the weight of mouse immune organs — thymus gland and splenic organ. While it could comprehensively enhanced the humeral immunity of mouse in the activation of phagocytic capability of macrophage, the enhancement of lysozyme activity and the promotment of formation of antibody in blood serum. The enhancement of the cutaneous delaye type hypersensitivity indicated that EPS is capable of improving specific cell immunity of mouse.This study theoritically and practically of great value, boasted the creation in the followed aspects. On one hand, it provided the direct experimental evidence that yoghurt had immunological function by researching the effect of EPS on immunological activity of mouse after the EPS extraction from yoghurt. On the other hand, the yield of EPS was increased by improving culture conditions. The purpose of this work was to produce more EPS-containing products, which would be applied to the new drug production in the future.