Bacillus belongs to the gram-positive bacteria, aerobic, can produce spores, is a class of highly active digestive enzyme system, high temperature resistance, stress resistance of heterotrophic bacteria. Bacillus can reduce the content of nitrate and nitrite in water, thereby playing a role in improving water quality. It can also compete with harmful algae and various pathogenic bacteria in the breeding environment to form a dominant population and play an inhibitory role.
1. Bacillus commonly used in aquatic products
Bacillus commonly used in aquatic products include Bacillus subtilis, Bacillus natto (a subspecies of Bacillus subtilis), Bacillus licheniformis, Bacillus coagulans, Clostridium butyrates and so on.
The characteristics of Bacillus are manifested in the following aspects:
1. Strong resistance to adverse environments: spores can resist drought, high heat, high acidity, high permeability environment, in a dormant state in harsh environments, and can bud and grow when encountering suitable conditions. When it reaches the right temperature, it can become a bacterium.
2. Most of the oxygen consumption: Bacillus is mostly strictly aerobic, and a few are facultative anaerobic or strictly anaerobic.
3. Large volume: 4-10 μm, the volume is four times larger than that of general pathogens, effectively inhibiting the reproduction of harmful bacteria.
4. Short life cycle: The time required for bacillus such as Bacillus subtilis to double is 1.5-2 hours, coming and going quickly, and the life cycle from the lower pond to the decay is 3-5 days.
▲Bacillus structure indication; Bacillus subtilis gram staining
Second, the influencing factors of the effect of spore microbial preparations
1. Dissolved oxygen in water: Most of the spores microbial preparations are aerobic bacteria or facultative aerobic bacteria (subtilis spores, compound spores), when using such live bacteria products, it is necessary to maintain the dissolved oxygen content in the water body to ensure the rapid reproduction of microorganisms and the rapid decomposition of organic impurities.
2. Dissolved oxygen at the bottom layer: The current biological bottom modification mainly uses a complex microbial preparation based on Bacillus subtilis, and a large amount of oxygen is required to be consumed at the same time. Especially in the middle and late stages of breeding, the bottom of the pond is the most polluted area, the oxygen consumption factor accumulated at the bottom will often make the bottom dissolved oxygen exhausted, although the use of biological bottom modification, but most of the bacteria dormant or do not reproduce, or even die, so in the late stage of breeding, conventional biological bottom modification is recommended with long-acting oxygenation preparations, or the use of strict anaerobic bacteria-based biological bottom modification, such as Clostridium butyrate-based bio-bottom kangtai.
▲Non-oxygen-consuming biological bottom modification - bottom Kangtai
3. pH: Under the photosynthesis of algae, the pH of the water body changes greatly, if in the low alkaline water body, the pH fluctuation value is greater, and Bacillus is the most active in the micro-alkaline water body. Low pH due to organic matter fermentation at the bottom of the pond can also affect the effectiveness of bacillus preparations.
4. Temperature: Most bacillus have good activity in 20 °C-37 °C, less than 10 °C when the vitality is poor, generally choose sunny morning, add an aerator to increase oxygenation, can make Bacillus products achieve the maximum effect.
5. Nutrient level of water: The reproductive rate of spore microbial agents after entering the water body has a great relationship with the nutrient level of the water body. It is generally believed that the utilization rate of bacterial growth on water bodies C, N and P is 100:5:1. If the water body is too thin, or the nutrient composition is single or unbalanced, some heterotrophic bacteria-based live bacteria preparations will not multiply in large quantities, and the use of live bacteria is almost ineffective, at this time, the lack of nutrients should be appropriately supplemented to the water body to achieve better results. At the same time, the presence of an appropriate amount of ammonia nitrogen, nitrite, hydrogen sulfide or organic matter is necessary, because bacteria can only obtain energy on this basis to survive and multiply, but excessive amounts will also have a toxic effect on microorganisms.
Third, the use of spores of microbial preparations
1. Water transfer: Take river crab farming as an example, such as too many organic impurities in the water body, the transparency is too low, the aquatic grass has been vaguely covered by the water color, affecting the normal photosynthesis of the aquatic weed, you need to use Bacillus, ammonia nitrogen, nitrite is high when the same use.
2. Bottom modification: The use of spore microorganism bottom change in the middle and late stages is recommended to be used in the order of "oxygen-bacteria-oxygen", that is, the first fourth week of the use of oxidative bottom change, the second and third weeks of the use of microbial bottom change, the rear stage of breeding appropriately increase the frequency of use.
3. Internal consumption: added to the feed for aquatic animals to eat to improve the gastrointestinal function of fish, shrimp and crabs, improve the profit rate of feed, improve meat quality, promote longevity, and have a good disease prevention effect. Mainly through the large number of bacillus to inhibit the breeding of harmful bacteria, there is a good metabolite, such as Clostridium butyric acid product can effectively repair intestinal epithelial tissue cells, repair the intestine.
Fourth, the selection of Bacillus
There are many bacillus preparation products on the market, mainly powder, and occasionally you can see water agents, so how to judge?
For bacillus preparation products with water agents, after the filling of bacillus preparations, because they are live bacteria, the spores are still growing, so the canned product container will have a gas bulge phenomenon. If the oxygen in the product is exhausted, a large number of live bacteria die, the water agent Bacillus preparation product is very unstable, under selective conditions, try to use powdered Bacillus products.
▲Lysophyrin (compound spore); water-rich beauty (subtilis spores)
Fifth, the correct use of Bacillus
There has been a debate about whether bacillus needs to be activated before use, usually in the laboratory to expand Bacillus, need to control temperature, moisture, oxygen, medium four conditions, to use glucose, starch, soybean meal, manganese sulfate, dipotassium phosphate, magnesium sulfate, calcium sulfate, ammonium sulfate, but also with adsorption carriers, such as wheat bran, zeolite powder. If it is a factory production, but also to purify and rejuvenate the strains, the use of fermentation tanks for expansion, connected to the aeration equipment, and constantly stirring, in the logarithmic growth stage of Bacillus, as long as the oxygenation is stopped for 30 seconds, the dissolved oxygen of the bacterial liquid can change from saturation to zero. The requirements of so many links are more difficult to operate in the pond mouth, so it is not recommended for farmers to expand the amount of bacterial liquid.
For the activation and use of spore products of Guangdong Biology: the strain, carbon source, water in accordance with the ratio of 1:3:45 soaked for about 4 hours, soaking needs to be aerated by the whole air pump, of which carbon element speed can be replaced by double the amount of brown sugar, water needs to use well water.
Sixth, some misunderstandings in the use of spore microbial preparations
1. No oxygenation during propagation, sealed fermentation. Many farmers use spore products in accordance with the fermentation method of EM and lactic acid bacteria, and the content of the fermentation liquid obtained by this method is extremely low, and the effect is greatly reduced, and it is recommended to use it directly without expanding.
2. Judge the quality of spore microbial preparations by producing gas. Bacillus does not produce a lot of gas when it meets water, usually a large number of yeasts are added to this type of product, and the content of Bacillus species is doubtful.
3. After using sporine products, you can use spore products for one week without water transfer (with other strains). Here to focus on it, under normal circumstances, the pond in the fungal phase has diversity and complexity, which is an important indicator to ensure the stability of the pond water body, a large number of supplementary Bacillus has destroyed the bacteriological phase of the pond itself, after 3-5 days of reproductive decay of Bacillus, the bacteriological phase of the pond will slowly recover, in the middle of which there will be a blank period, which will lead to the proliferation of harmful bacteria, the change of the bacterial phase will drive the change of the algal phase, and there will be serious inverted algae and water. After using Bacillus for three days, it is recommended to take measures to replant EM strains (EM water king) and carbon sources (carbon velocity) directly splash water to quickly restore the bacterial phase of the pond.
▲ Combination of recovery bacteria
Bacillus in aquatic products in the water quality improvement, disease prevention, physique enhancement and other aspects have an important role, scientific and reasonable use of Bacillus can achieve the effect of half the effort, but also recommended that the majority of farmers in the choice of spore products to choose high content, large factory brand products, and finally wish everyone a successful breeding.