Studies On The Effects Of Acetobacter Tropicalis In Aquarium And Physiological Characteristics In Nile Tilalpia

In this paper physiological characteristics,the fermentation condition and optimized medium of Acetobacter tropicalis were studied.Meantimes, the study was conducted to examine effects of indexes of COD,NH₄⁺-N , the weight gain rate , intestinal digestive enzyme activity and immune performance by feeding with diets containing Acetobacter tropicalis in Nile Tilalpia ,which provide scientific base for application in aquaculture.The paper included four experiments:Part 1 Studies of physiological characteristics and optimized medium of Acetobacter tropicalisThe morphological,cultural,physiological and biochemical characteristics of Acetobacter tropicalis were analyzed.The result indicated that Acetobacter tropicalis was gram-negative,single or chain,small rod measuring approximately 0．5 to 0．7 by 1．8 to 2．0μm.The clone shape was circular.Their surface was glazed .They were able to grow under the conditions of pH 3．7 or pH 4．5 and ethanol concentration 5 %.The strain could utilize Glucose,O/F, acetate and D-fructose,but could not utilize gum sugar, starch, inositol, maltose, D-mannitol, D-xylose and Glycerol.The test of nitrate reduction and catalase was negative.The result indicated that the concentration of Acetobacter tropicalis achieved maximum after about 14 hours, that pH in the liquid of fermentation decreased gradually with the change of time and reached 3．17 after about 40 hours, They were able to grow under the condition of salt water。The fermentation condition of strain were investigated through single-factor and uniform design tests. The most suitable medium was identified as following: glucose 0．25%, KH₂PO₄ 0．1 %,(NH₄) ₂SO₄ 1．0 %,yeast extract 0．5 %,distilled water 100mL .The optimized fermentation conditions and medium were: temperature 37℃, initial pH 4．5, and shaking at 100 r/min, 6% inoculum, bottle measure 70/150 mL.Temperature and nitrogen source were important role for growth of the strain.Part 2 The effect of application in aquariumThe control group was fed with basal diet, and the others were the treated groups fed with basal diet supplemented with 1%,2%,3% and 4% Acetobacter tropicalis for 13 days,respectively. Measures NH₄⁺-N and COD of strain on schedule. The result showed that values of the control group and the treated groups'COD were 23．46 mg/L,22．60 mg/L,19．83 mg/L,16．65 mg/L,15．22 mg/L, that Values of their NH₄⁺-N were 205．31μg/L,195．26μg/L,161．44μg/L,131．71μg/L,107．85μg/L ,respectively.The application of bacillus culture could efficiently decompose pollutants and the organic substances in the aquarium.Decontamination increased gradually with the change of concentration of Acetobacter tropicalis.Part 3 Effect of Acetobacter tropicalis on the intestinal digestive enzyme activity of Nile TilalpiaThe control group was fed with basal diet, and the others were the treated groups fed with basal diet supplemented with 1 %,2 %,3 % and 4 % Acetobacter tropicalis (10cfu/ml) for 30 days , respectively.It's effect on growth rate of Acetobacter tropicalis weights and digestive enzyme activity in intestinal canal.The results showed, adding 4% Acetobacter tropicalis ,the weight gain ratio and proteinase activity increased by 15．89 % (p<0．05) , and 33．1 % (p <0．05) , respectively.But had no significant effect on intestinal amylase activity .Containing 3% Acetobacter tropicalis in the basal diet, lipase activity increased significantly (p<0．05) .Surpass this adding dosis, lipase activity in intestinal canal showed descending tendency.In a word, Acetobacter tropicalis could improved intestinal digestive enzyme activity and the weight gain rate of Nile Tilalpia.Part 4 Effect of Acetobacter tropicalis on immune performance of Nile TilalpiaTreatment 1 was the control group fed with the basal diet, the others were the treated groups fed with diets containing 1%, 2%, 3%, 4% Acetobacter tropicalis ,respectively.Adding the 3% Acetobacter tropicalis, serum Lysozyme activity, serum SOD activity, serum AKP activity and serum ACP activity increased by 40．57 %, 11．98 %, 20．4 % and 55．1 %,respectively (p<0．05) .Surpass this adding dosis, serum Lysozyme activity, serum AKP activity and serum ACP showed descending tendency.In conclusion, that Acetobacter tropicalis as feed supplementeds to Nile Tilalpia was a fine probiotics that can improve the weight gain rate and intestinal digestive enzyme activity and immune performance.Key words: Acetobacter tropicalis; Nile Tilalpia ;physiological and biochemicalcharacteristics; NH₄⁺ COD; intestinal digestive enzyme activity; immuneperformance...