Isolation, Domestication And Microencapsulation Of Lactobacillus Acidophilus From Piglets

Lactobacillus acidophilus as important probiotics in animal’s intestines, has many functions, such as mainteining the health of the animal’s gut, alleviating the stress, improve the breeding environment, regulating the bogy’s fat metabolism and improve the quality of the livestock products. Lactobacillus probiotics are gradually being used as an animal feed additive. In this study, a strain of Lactobacillus acidophilus has been isolated from the piglets’faeces. Their tolerance of the condition in gastrointestinal tract has been improved by domestication, and their micro-capsule has been developed. The research results are as the following:(1)13 strains of Lactobacillus suspects have been gained by the dilution method suing MRS agar from 15 day-old piglets’faeces, without feed any antibiotics. However, only nine strains of lactobacilli have been identified through physiological and biochemical test. After the carbohydrate fermentation assay, four strains named as strain La-5, La-6, La-8 and La-9 presumably belonged to Lactobacillus acidophilus. Strain La-5 has been selected as the sample of this study by comparing their morphology, growth and acid productivity among four strains, Strain La-5 is identified as Lactobacillus acidophilus using 16 S rDNA homology analysis, and physiological and biochemical tests.(2) A strain La-5c, tolerating low pH, high temperature and high cholate, has been picked out using the method of gradient subculture domestication, The result of strain La-5c’productivity of acid showed that, the total acid concentration was 12.88g/L which has increased by approximately 4.8 times compared with the control (blank fermentation medium) after 48h fermentation in MRS liquid fermentation medium. It indicated that, strain La-5c had a good acid productivity and was suitable for animal feed additives.(3) It was indicated that Lactobacillus acidophilus La-5c has good prebiotic effects including safe, no toxic side effects, significantly increasing the body weight of the mice, decreasing in the use of feed, promoting the absorption and transformation of nutrients, significantly improving the mice growth and developing the immune organs by the assay of safety and prebiotic effect evaluation through the methods of using Lactobacillus acidophilus La-5c as feed additive feeding mice.(4) It showed that three microcapsule material of acacia, trehalose and maltodextrin developed the growth of Lactobacillus acidophilus La-5c by the compatibility test between the wall materials and strain La-5c. Orthogonal design test revealed that the best ratio of three kinds of microcapsule wall material were 2.0%gum arabic,5.0%trehalose, and 11.0%maltodextrin. The number of viable cells were 12.56 × 10 cfu·g-1. Samples Observation Method (survival as an index) has been used to measure the stability of the microcapsules of Lactobacillus acidophilus La-5c. The results showed the microcapsules using the ratio of wall materials was a good stability with the cell concentrations and the survival rate of Lactobacillus acidophilus La-5c respectively 8.57×108 cfu·g-1 and 68.2% after 180 d.