| The mechanism of action of the probiotic bacteria has not been studied systematically. According to some recent publications, in the aquaculture the mechanism of action of the probiotic bacteria may have several aspects. 1. probiotic bacteria may competitively exclude the pathogenic bacteria or produce substances that inhibit the growth of the pathogenic bacteria. 2. provide essential nutrients to enhance the nutrition of the cultured animals. 3. provide digestive enzymes to enhance the digestion of the cultured animals. 4. probiotic bacteria directly uptake or decompose the organic matter or toxic material in the water improving the quality of the water. |
| Chinese researchers have done some studies on the probiotic bacteria to improve the shrimp culture water, and achieved remarkable results (Li Zhuojia et al 1997). For example, when photosynthetic bacteria was added into the water, it could eliminate the NH3-N, H2S and organic acids, and other harmful materials rapidly, improve the water quality and balance the pH. The heterotrophic probiotic bacteria may have chemical actions such as oxidation, ammoniafication, nitrification, denitrification, sulphurication and nitrogen fixation. When these bacteria were added into the water, they could decompose the excreta of fish or prawns, remaining food materials, remains of the plankton and other organic materials to CO2, nitrate and phosphate. These inorganic salts provide the nutrition for the growth of micro algae, while the bacteria grow rapidly and become the dominant group in the water, inhibiting the growth of the pathogenic microorganisms. The photosynthesis of the micro algae provide dissolved oxygen for oxidation and decomposition of the organic materials and for the respiration of the microbes and cultured animals. This kind of cycle may improve the nutrient cycle, and it can create a balance between bacteria and micro algae, and maintaining a good water quality environment for the cultured animals. |
| Based on the previous research results on probiotics we suggest that the use of probiotic bacteria in aquaculture has tremendous scope and the study of the application of probiotics in aquaculture has a glorious future. At present, the probiotics are widely applied in United States of America, Japan, European countries, Indonesia and Thailand, with commendable results. The probiotics have become commodities in some countries, for example, the Alken-Murray Corporation and American Standard Products company of United States of America and the company of Japan have their probiotics products. The study may create a new field of industrial products, like the industrial fields of aquaculture product processing and Aquacultural food processing. |
| China is a large country in aquaculture, but the application and development of the probiotics in Chinese aquaculture is very meager when compared to other countries. In recent years, the diseases of shrimps hindered the development of shrimp culture. The Chinese government has realized the economic value and potential social benefits of the application of probiotics in aquaculture, and has, recently, paid more attention to the study and development of probiotics in aquaculture. Thus the government has increased the research funds for it. Probiotics principally inhibit the growth and decrease the pathogenicity of the pathogenic bacteria, enhance the nutrition of the aquacultured animals, improve the quality of the aquaculture water and decrease the use of antibiotics and other chemicals; thus decreasing environmental contamination by the residual antibiotics and chemicals. This benefit of probiotics will be long lasting, and the application of probiotics will become a major field in the development of aquaculture in the future. |