The application of Probiotic PSB or Photosynthetic Bacteria in Aquaculture
The main goal of using this PSB bacteria is to develop microbial-controlled ponds or human made ecosystem such as tanks or aquarium, which will give us as a stable control over processes inside.
The development of non-antibiotic and environmental friendly agents is one of the key factors for health management in aquaculture. In Aquatic species such as fish and shrimp, the occupation of the gastrointestinal tract begins right after hatching and is completed within a few hours to modulate expression of genes in the digestive tract, thus creating a favorable habitat for them and preventing invasion by other bacteria introduced later into the ecosystem (Balcázar et al., 2006).
One of the probiotics used in Asian aquaculture are mainly photosynthetic bacteria (PSB), Purple non-sulfur bacteria are widely distributed in freshwater, marine, soil and hotspring environments, which can be favorable in Asia due to its tropical weather. It have various metabolic pathways for the degradation of organic wastes, which is one of the key points for a clean and stable pond.
They also have a more digestible bacterial cell wall, and are rich in proteins, carotenoids, biological cofactors, and vitamins (Kobayashi and Kurata, 1978). It was reported that the addition of photosynthetic bacteria as food additives stimulated the growth of shrimp and fish (Zhang et al., 1988), enhanced the survival rate of fish larvae, and improved the production of scallop seed (Huang et al., 1990; Wang et al., 1994).
They were also found to increase the population growth rate of live food such as Brachionus plicatilis (Xu et al., 1992). Furthermore, some plant and herb extracts were identified as growth promoter for the mass cultivation of photosynthetic bacteria (Xu et al., 1994). The technique which uses photosynthetic bacteria as probiotics has become common practice in aquaculture in few countries in Asia such as China, Taiwan, Thailand, Vietnam, and Indonesia.
Many commercial photosynthetic bacterial products are labeled as either single or multiple species at concentrations higher than 1 billion CFU/ml, depends on what is wanted to achieve, and are often combined with growth promoters or conditioners, and are claimed to have multifunctional effects such as improvement of water quality, enhancement of growth rate and prevention of disease (Zizhong Qi , Xiao-Hua Zhang ,Nico Boon , Peter Bossier).
Maeda and Nagami (1989) reported some aspects of the bio-controlling method in aquaculture. In their study bacterial strains possessing vibrio (waterborne bad bacteria) stationary activity which improved the growth of prawn and crab larvae were observed. By applying these bacteria in aquaculture, a biological equilibrium between competing beneficial and deleterious microorganisms was produced, and results show that the population of Vibrio spp., which frequently causes large scale damage to the larval production, was decreased.
Survival rate of the crustacean larvae in these experiments showed much higher than those without the addition of bacterial strains. They hope that addition of these strains of bacteria will repress the growth of Vibrio spp., fungi and other pathogenic microorganisms.
Their data suggest that controlling the aquaculture ecosystem using bacteria and protozoa is quite possible and if this system is adopted, it will maintain the aquaculture environment in better condition, which will increase the production of fish and crustaceans.
Characteristics of Photosynthetic Bacteria (P.S.B.): • P.S.B. is used for maintaining the quality of water and bottom pond soil. • P.S.B. is poisonless and requires very little oxygen. Thus, P.S.B. will not exhaust the oxygen in the pond. • Posses an excellent capacity of purifying water quality. It is so called scavenger of pond.
Functions: • Improve the water quality of pond. • Contain special active bacteria which can decompose toxic matters like the organic materials, hydrogen sulfide, nitrous acid, ammonia, and pond sludge. • If raining, the pond may be easily polluted by acid rain. P.S.B. can purify the water quality and increase capacity of oxygen dissolution. • Increase the capacity of disease resistance • Efficiently decrease BOD, COD, SS (suspended substances) and improve water quality. • Prevent fishes and shrimps from disease and ensure their health. Reduce the use of antibiotics and chemicals. • Restrain pathogenic bacteria counts in the water to diminish diseases for animal. • Rich in nutrition. • Contains plentiful protein, vitamin B and so on. Add in feedstuff can supply additive nutrition which is lacked in normal feedstuff. • Contain large amount of carotene and vitamin A and D. P.S.B. can enhance the body color of fishes and shrimps. • Improve the appetite and digestion of fishes and shrimps. • Promote the growth of botanical plankton.