The Study Of Bacillus Polymyxa Strain On Degradation Of Protein And Promoting Fish Bodies Nutritive Material Absorption

This study gathered the intestinal contents of fresh common carp from the breeding ponds and lakes in Sichuan. Carries on selection have certain proteinase-producing ability bacillus strain after the gathering sample, altogether separates and purifies to 55 strains, then chosen 19 strains which all have proteinase-producing ability, to carry on the advance screening. Finally, we screen one to have the high proteinase-producing ability and the effect stable strain to the milk culture medium, after the appraisal, we sure that this strain is Bacillus polymyxa strain, and named A7. The strain has tolerance to bile salt concentration of 0.5% and pH2.5 ability. The experiments show that the strain of A7 has significantly inhibitory effect on the aquaculture-conditional pathogennic bacteria Aeromonas hydrophila and then thought hemolytic test, small white mouse safety test and common carp safety test finally we determination A7 safety on aquaculture.Adopted solid fermentation medium is corn meal 300g,wheat bran 400g,soybean meal 300g and phosphate butter 500mL. The optimization experiments of solid fermentation results shows that culture conditions included: temperature 28℃, capacity ratio 16%, material and water ratio 1:1.0, inoculation quantity 5%, fermentation time 48h,drying time 48h. The strain revival ration is above 60% on the solid fermentation broth storage at normal temperature of one mouth..Using A7 solid fermentation broth mixture of diets fed common juvenile carp fish, the trial was carried out 50d. The results showed that the addition of A7 in foundation diets experiment group average of growth rate has the control group 1.23 times and specific growth rates higher than the control group, though the addition of yeast in foundation diets experiment group average of growth rate has lower than the control group 2.1% and specific growth rates lower than the control growth. The apparent digestibility of dry-matter and crude protein feed ingredients which addition of A7 in foundation diets experiment group has been 65.85% and 85% respectively, significantly higher than other test groups(P<0.05).To the A7 strain degeneration protease, produces the enzyme condition and the enzyme activity research discovery that the optimally produces the enzyme temperature of the strain is 37℃, pH value is 7. The strain in 28℃,110Or/min water shake cultivation 72h,produces the enzyme quantity to achieve the highest, its enzyme activity is 2998U.The in vitro digestibility of 4 feed protein ingredients i.e. fish meal, soybean meal, rapeseed meal and cottonseed meal for common carp was studied by means of the in vitro digestibility method in the experiment. The results shows that there was no significant in all different test in vitro dry-matter digestibility and crude protein coefficient for fish meal, though there was significant in all different test in vitro dry-matter digestibility and crude protein coefficient for soybean meal, rapeseed meal and cottonseed meal.