The Optimization Of Fermentation Conditions Of B. Subilis Natto NAT1 And The Effects On Immunity And Growth Performance In Chickens

Antibiotics supplementaries used in chicken feed are aimed for preventives and promoters of growth, However, they caused many negative effects, and the most serious one is resistance. The resistance leads to cureless of a number of bacterial diseases. In this case, more advanced antibiotics are needed, but the speed of bacteria mutation is too fast to get new antibiotics for each mutation. This also happened for the drug using problems of human in the past two decade years. In this thesis, three experiments were conducted to explore if B subtilis natto could substitute the antibiotics in chicken feeding,. In experient 1, B subtilis natto was cultivated using soybean meals, and the outputs reached 101 CFU/g. In experiment 2, the characteristics of B subtilis natto applied to feed addictives were researched. In experiment 3, chickens were fed B. subtillis natto for 35 days. The effects of B. subilus Natto in growth performance and immunity were tested.In experiment 1, a single facter analysis was used to determine the effects of carbon source, nitrogen source, yeast extract, and dissolved oxygen respectively. The highest OD600 value was reached using 3% glucose,5% soybean leach liquor,0.75% yeast extract and 20ml fermentation liquor in a 300ml flask. Dissolved oxygen is the most important one among the four facters. Then it is found that there was a highest OD600 value about 12 when the medium contained 3% glucose,5% soybean leach liquor, and 0.75% yeast extract and 20ml fermentation liquor in a 300ml flask by an orthogonal experiment. From the growth curve, the amount of B. subtillis Natto went into a stable stage after cultivated for 10-12h, while the OD600 value reached 10.24. The spore yield came to 1.2×1010CFU/g counted by coating.In experiment 2, the characteristics of B. subtilis Natto in chicken feeding was tested in order to determine whether the spores are suitable for feed processing and avoiding the damage of digestive juice or not. The spores were able to stand up with high tempreture of 100℃ for 10 mins and gastic juice for 4 h, and the results also show that there were 92 percent survived from the simulated bile salt. Moreover, bacillus subtillis natto can secrete some feed-enzyme, especially amylase and protease with 1500u/g and 5000u/g activities value, respectively.In experiment 3, chickens were fed with B. subtilis natto concentration of 1.8× 10 for 35 days. Faeces, blood, tissues and digestive tracts were collected punctually, meanwhile, feed conversion, bacteria concentration, oxygen burst of heterophile and immune globulins were also detected. The results showed that B. subtilis natto can increase feed conversion about 10%, and improve the consentration of lactobusilus. The quantity of spores in the faeces increased comparing to the spores fed by chickens, therefore we conclude that the spores can germinate and proliferate in the intestine tracts.In addition, B. subtilis natto also enhanced oxygen burst of heterophile, phagocytic function, and the concentration of immune globulins.The consequences elicited that B subtilis natto can be suitable for scale production by using of soybean, and is also able to be an alternative of antibiotics aiming for immunizing. There will be great application potential in chickens industry, even the whole animal husbandry.