Construction Of Engineered Lactobacillus With Endoglucanases Activity And The Effect Of Application For Rabbits

Agricultural straws and foragesare indispensable substances for animal breeding, they can not only supply vitamins and minerals which nimalrequired, but also promote gastrointestinal motility and improve digestibility. But straws and forages contain large amounts of cellulose, which special structure is difficult to be degraded and absorbed in the gastrointestinal tract of animals. The intestinal microorganisms of animals producedcellulase to degradecellulose. Therefore, it is an effective way to get cellulase that screening for cellulose degrading microorganisms. Lactic acid bacterias live in intestines of animals, and compete or produce lactic acid and other metabolites to antagonize the rapid proliferation of harmful microorganisms, that promoting growth and immunity of animals.Thus, lactobacillus is an effective substitute for antibiotics. The present study was to investigate:(1) This study aimed to isolate,screen and identify the cellulose-producing bacterium and lactobacillus from the cecal and ileum contents of Rex rabbit, and analysised enzymatic characteristics of the cellulose-producing bacterium, respectively. A cellulose-producing bacterial strain namedBacillus subtilisand lactobacillus named Lactobacillus plantarum were isolated and screened. The cellulase activity ofBacillus subtiliswas the highest when grown at 37 ℃, pH 7.0 for 24 h. The optimum temperature and the optimum pH of enzyme-substrate reaction were 60 and ℃ 7.0, respectively. In addition, the enzyme in pH range 4.0~8.0 have a strong acidic and basic stability.(2) Amplified endoglucanase gene of Bacillus subtilis by primers and connected with expression vector of pLEM 415, then cloned into Lactobacillus plantarum, whichthe Lactobacillus plantarum had0.046U/mL activity of cellulase.(3) This study we want to explore the effect of endoglucanase-producing lactobacillus on growth and immune performance of 30d- Rex. Sixty rabbits were randomly divided into three groups, 20 rabbits in each group and group A and group B were fed endoglucanase-producing lactobacillus, lactobacillus plantarum, respectively,andgroup C was control group. Every two days fed 10 mL(107 cfu/mL). 4 d for pre-feeding period and 31 d for test. Selected 10 of each group to slaughter after 35 d and determined growth and immune performance of each group rabbits. The results showed that the endoglucanase-producing lactobacillus can significantly reduce feed conversion ratio, improve performance of Rex. At the same time, the engineering lactobacillus also can significantly improve the Rex eviscerated yield and immunity...