The Effect Of Co-Culture Of Probiotics And Sodium Alginate Microspheres On The Environmental Tolerance Of Probiotics

The present study focuses on the probiotic Lactobacillus planetarium 550 and uses the method of first embedding and then culturing to prepare alginate-calcium-based probiotic microcapsules.The study investigates how changes in internal structural factors such as apparent morphology,mechanical properties,and viscoelastic behavior during the cultivation process affect the in vitro digestive properties,storage properties,UV stability,and freeze-drying stability of the probiotics.Furthermore,the study employs this method to produce alginate-sodium alginate-pectin probiotic microcapsules and alginate-sodium alginate-pectin-phospholipid probiotic microcapsules and explores their swelling properties and colon-targeted release properties.The main conclusions drawn from the experiment are as follows:(1)Probiotic microcapsules prepared using alginate sodium as the raw material and the method of first embedding and then culturing can significantly improve the simulation digestive and storage properties of the gel beads.Experimental results show that after embedding the bacteria in the gel beads and culturing them in MRS broth for 24 hours,the external pH value stabilizes at 3.71±0.035 and no longer decreases.Under the same culture conditions,the pH value of the sample without Lactobacillus planetarium 550 remained stable at 5.95±0.05.The porous structure and surface crack structure of the alginate gel beads provide conditions for the growth of probiotics.After 24 hours of cultivation,it is possible to obtain 10-11 Log CFU/g of viable bacteria,which is about 3-4 Log CFU/g higher than traditional methods.In vitro simulated digestive data shows that the average number of viable bacteria in the ALP group decreased by 1.09 Log CFU/g,while the CLP group’s average number of viable bacteria decreased by 2.81 Log CFU/g,and the bacterial damage in the CLP group was about three times that of the ALP group.After 6 hours of digestion,the final number of viable bacteria in the ALP group was greater than 9 Log CFU/g.Furthermore,the microcapsules can protect the probiotics during storage at 4℃ and25℃,and there is no significant difference in protection effect among different concentrations of alginate sodium.(2)Probiotic microcapsules prepared using alginate sodium-pectin can improve the in vitro digestive and UV stability of the gel beads.Compared with the previous chapter,the addition of pectin had little effect on the growth of probiotics in the gel beads and the external pH value.In terms of apparent morphology,2ALP-2P had the largest particle size,which was 3.049±0.126 mm.With increasing pectin concentration,the microcolony morphology gradually increased.In terms of internal structure,the texture results showed that the hardness of the gel beads would decrease with increasing pectin concentration.The lowest hardness was 439.675±96.656 for 2ALP-2P,but the overall cohesiveness and resilience showed an upward trend,with the highest 2ALP-1P being 0.689±0.017 and 0.314±0.015,respectively.Pectin also helps to enhance the adhesion of the gel beads.Rheological analysis shows that the increase in G’ indicates that pectin and Ca2+ undergo crosslinking.In terms of probiotic protection,the in vitro simulated digestion results show that about 14.32%of the probiotics in 2ALP were released into the gastric fluid within the first hour,leading to continued damage to the probiotics.The release percentage of viable bacteria in the first hour of intestinal digestion was the smallest in 2ALP-2P,at 0.56%,and after the intestinal digestion phase ended,the release proportions of 2ALP-1P and 2ALP-2P were 0.53% and 0.61%,respectively.In UV stability tests,the overall survival rate showed a rapid increase followed by a slow rise as the pectin concentration increased,with 2ALP-1P and 2ALP-2P showing good probiotic protection,with survival rates of 78.26% and 79.37%,respectively.(3)Probiotic microcapsules prepared using alginate sodium-pectin-phospholipid can significantly improve the apparent morphology,mechanical properties,viscoelasticity,hydrophobicity,colon-targeted release performance,and UV and freeze-drying stability of the gel beads.In terms of apparent morphology,2ALP-1P-3L had the largest particle size,which was 3.217±0.107 mm.Furthermore,microcolony morphology could still form after phospholipid was added,and the size and unevenness of the microcolonies improved slightly with increasing phospholipid concentration.In terms of internal structure,2ALP-1P-3L with high concentration phospholipids enhanced the hardness and chewiness,reaching 720.404±40.866 and 356.021±22.853,respectively.At the same time,it increased the storage modulus,and the effect of enhancing the gel structure weakened with increasing phospholipid concentration.In terms of colon-targeted release performance,samples that had been additionally supplemented with phospholipids were almost insoluble in environments with pH values between 6 and 9,indicating that phospholipids could effectively increase the hydrophobicity of the gel beads.In vitro simulated digestive results show that the average release of viable bacteria in samples with additional phospholipids was as high as 9.32±0.07 Log CFU/g after being continuously digested for 9 hours.In terms of probiotic protection,UV stability analysis results show that microcapsules supplemented with phospholipids can effectively improve their UV resistance,with the survival rate of 2ALP-1P-2L reaching 95.98% before and after exposure to UV light.In freeze-drying stability testing,the logarithmic percentage of viable bacteria in the two samples,2ALP-1P-1L and 2ALP-1P-2L,supplemented with low concentrations of phospholipids,can be up to 108.80% and 108.04%,respectively.