Studies On Fermentation Technology Of Aquaculture Probiotics

Since the 1980 s, with the rapid development of aquaculture, which courses the model of aquaculture has changed from the extensive farming into intensive and high-density culture. Aquaculturists continue to increase breeding density because of the blind pursuit of economic interests, which lead to the deterioration of water quality and outbreak of diseases. They are still using the antibiotics to control the diseases, which not only course the drug resistance of pathogen, but also the drug residues in aquatic products which is harmful to humans. In recent years, the use of probiotics as feed additives and water conditioner, which has been proved that can allivate the diseases and approaching healthy culture. The probiotics have greatly possibilities to replace antibiotics and becoming a new way to prevent and treat diseases. With the deepening research of the mechanism of probiotics for aquaculture, more types of probiotic bacteria have good effects on aquatic animal will be found. Using the strains of these probiotic bacteria for fermentation and find the most suitable fermentation process has become a new direction in the research of aquaculture probiotics.This study focused on the fermentation prcess of two strains probiotics Bacillus subtilis B1884 and Aquabiodomus nitratireducens A762, which were isolated from the aquaculture water. Begining with choosing the material from the leftover material of agricultural products through the single factor experiment in order to find the optimal carbon source, nitrogen source and inorganic salt. And then optimizing their proportion through the orthogonal experiment. These data included the followings: The optimal material of medium for strain B1884 were wheat bran powder, peanut meal powder, KH2PO4. The optimal material of medium for strain A762 were molasses, peanut meal powder, Na2HPO4. The optimal fermentation formula of strain B1884 was composited of wheat bran powder 5 g/L, peanut meal powder 15 g/L, KH2PO4 10 g/L. The optimal fermentation formula of strain A762 was composited of molasses 5 g/L, peanut meal powder 15 g/L, Na2HPO4 10 g/L. The study above was under the condition of 500 ml flask.Other fermentation parameters for strain B1884 and strain A762 were optimized on the base of the resulting fermentation medium in the 500 ml flask, they included: temperature, original p H-value, rotation speed, amount of inoculation etc. The obtained best fermentation condition for strain B1884 was described as: the best fermentation temperature at 38 degree, original p H 7.0, amount of inoculation 3%, amount of load 150 ml(in 500 ml, flask), rotation speed 220 rpm. The obtained best fermentation condition for strain A762 was described as: the best fermentation temperature at 28 degree, original p H 6.5, amount of inoculation 5%, rotation speed 300 rpm, amount of load 150 ml(in 500 ml, flask).The final optimized system allowed the total number of strain B1884 to 1.11×1010 CFU/ml and the number of spores to 9.33×109 CFU/ml. The spore production rate reach 84.05%. The final optimized system also allowed the total number of strain A762 to 1.28×1010 CFU/ml.At last, the optimized technology was applied in 5L fermentation tank production, the result described as follow: The total number of strain B1884 reaches 7.96×1010 CFU/ml and the number of spores reaches 7.12×1010 CFU/ml. The spore production rate reaches 89.6%. The total number of strain A762 reaches 3.91×1010 CFU/ml. Comparing to culturing in 500 ml flask, the fermentation tank has the effect of amplification. This kind of optimized technology has great application value.