Interaction Between Lactobacillus Rhamnosus GG And Encapsulating Materials In Microcapsules

In order to strengthen the resistance of probiotics to pH,extreme temperature and other harsh environmental factors for extending the storage time,a variety of microcapsule embedding technology were developed.Therefore,how to comprehensively analyze and evaluate the interaction between microcapsule system and microbes has gradually become an urgent problem.In this experiment,the interactions between the microcapsules of Lactobacillus rhamnosus GG and the embedding materials were preliminary discussed at the cell and molecular biology level.And then it was used as an important basis for evaluating the protective effect of microencapsulated system on LGG during long-term cryogenic storage.The main results are as follows:(1)Based on our previous studies,sodium alginate(SA)or carboxymethyl chitosan-sodium alginate(CMC-SA)mixed solution was introducted as the material to encapsulate LGG by modified extrusion method.The embedding rates of LGG in SA microcapsules and CMC-SA microcapsules were 54.62 ± 0.02%and 50.05 ± 0.01%,respectively.(2)The infrared spectrum showed that both of the aboved materials could successfully embed LGG in the microcapsules.During long-term cryogenic storage,the CMC-SA microcapsules were less affected by the environment and the microbes.However,the SA microcapsules may undergo slight material degradation,which leads to the leakage of LGG from the microcapsules.Therefore,it seemed that CMC-SA microcapsules exhibit better storage stability than SA microcapsules.(3)The effects of embedding materials on LGG survival rate,cell surface potential and cell membrane permeability under long-term cryogenic storage were investigated.The results showed that,after 4 weeks of cryogenic storage,the zeta potential of LGG in SA and CMC-SA microcapsules was stable at 30 to 45 mV.The loss of LGG viability was 1.30 ± 0.03 and 1.12 ± 0.03 Log10 CFU/mL and the PI absorption factors were 1.45± 0.03 and 1.28±0.01,respectively,which were significantly lower than the non-embedded group.Although the early protection of CMC-SA microcapsules was not good,the protective effect of CMC-SA microcapsules on LGG pronounced better than SA microcapsules in longer storage periods.(4)When the microcapsules were re-cultured in the broth after 4 weeks reservation at low temperature,the lactate dehydrogenase activity of LGG in the CMC-SA microcapsules was found at 21.51 ± 0.74 U/L,which was significantly higher than that in the non-embedded group and the SA microcapsules.Meanwhile,proteomic studies have shown that neither of the two microcapsules can maintain the normal expression of enzymes related to glucose metabolism in LGG,such as pyruvate kinase and glyceraldehyde-3-phosphate dehydrogenase.The expression of the proteins related to the transcription and translation of LGG,such as 30S ribosomal protein S3 and 50S ribosomal protein L2,which was significantly decreased in SA microcapsules and non-embedded group,was maintained at the normal expression level in the CMC-SA microcapsules.It is clearly indicated that,compared with SA microcapsules,microcapsules prepared with carboxymethyl chitosan-alginate composites could maintain the protein expression and cell metabolism of LGG,and provide a better protection for LGG during the long-term cryogenic storage.