Apply enzymes to improve water quality and pond bottom
Application of enzymes to improve water quality and pond bottom
Elisabeth Mayer, BIOMIN Austrian company
In aquaculture, the deterioration of water quality and sediment quality has become increasingly serious and widespread. This article focuses on possible ways to improve water quality and substrate quality. A better breeding environment will inevitably improve the overall production performance of farmed fish and shrimp.
With the expansion and development of the aquaculture industry, several challenges have gradually emerged. A key issue caused by aquaculture is its environmental impact. High-density aquaculture pond systems produce high organic matter loads that cause deterioration of water quality and sediment quality as well as accumulation of toxic compounds such as ammonia nitrogen, nitrite, and hydrogen sulfide. As a result, the composition of microorganisms in the water and pond bottom has been changed, which has led to an increase in pathogens, which in turn has led to the occurrence of diseases.
Direct application of enzyme
One way to improve water quality and sediment quality in aquaculture is to apply enzymes and beneficial microorganisms directly in culture ponds. This type of biotechnology application, often referred to as "bioremediation", is an environmentally friendly means of applying beneficial microorganisms in ponds to reduce pathogens, enhance mineralization of organic matter, and use specific enzymes to remove hazardous waste.
In the bioremediation process, the enzyme acts as a catalyst to accelerate the biochemical reaction in the substrate and water. When the enzyme is added to water or spilled on the bottom of the pond, the enzyme can degrade the main organic components commonly found in shrimp ponds and fish ponds.
Each enzyme has its mechanism of action and is specific in its catalyzed chemical reactions. For example, proteases hydrolyze insoluble proteins, amylases hydrolyze polysaccharides such as starch; cellulases catalyze the breakdown of cellulose (cellulose is the main constituent of plant cell walls); beta-glucosidase is involved in the catalysis of plant debris Hydrolysis and biodegradation of various β-glucosides; lipase acts on lipids.
Enzymes can be naturally produced and secreted by certain microorganisms. These extracellular enzymes such as cellulases, proteases, amylases are produced in the aerobic fermentation of microorganisms by microorganisms, such as certain Bacillus species. Bacillus is commonly found in pond sediments and can also be added to pond water for bioremediation. Some Bacillus can also degrade nitrogen-containing compounds, and the various (extracellular) enzymes they secrete help accelerate the decomposition of organic matter and toxic compounds such as ammonia nitrogen.
Some specific enzymes are active under a wide range of environmental conditions. For some microorganisms, the environmental conditions (pH, oxygen, etc.) that can proliferate are narrow. Certain enzymes can work in a variety of environments. These enzymes remain active even when the environmental conditions change drastically, especially when these enzymes are adsorbed by the carrier. For example, proteases can be effective at pH 4-11, temperatures below 20 ° C and above 70 ° C.
In addition to this, another advantage of adsorbing the protease to the carrier is that it retains the enzyme activity and can therefore be reused.
Enzyme preparations have attracted a lot of attention in recent years, despite their high cost of separation, purification and production. Some of these products have been used in aquaculture as bioremediation preparations.
Bioremediation has proven benefits
The enzyme stabilizes the organic matter in the substrate and can be used to effectively manage the substrate and culture conditions. No specific enzyme works best in all situations. Combining several enzymes for bioremediation in aquaculture may be the most effective method. Considering the efficiency and mechanism of action of the enzyme, the selected enzymes are required to have:
1 Catalytic degradation of organic matter (such as feces, and dead algae)
2 can break down large sludge particles ( -flocculation) and reduce siltation
3 reduce solid matter
4 decomposition of plant debris
5 to reduce the anaerobic conditions at the bottom of the pond
6 promote the degradation of certain complex nutrients
7 contribute to the release of digestible nutrients
Enzymes can significantly reduce siltation and reduce anaerobic conditions at the bottom of the pond. They promote the faster degradation of organic matter accumulated at the bottom of the pond, especially under high-density culture conditions. These organisms include pathogenic microorganisms in residual baits, dead algae, mineralized mud, manure and sediment, while pond bottoms are usually in an anaerobic condition. However, for all of these enzyme-catalyzed bioremediation processes, the presence of beneficial microorganisms is also important. The enzyme accelerates the action of the microorganism by decomposing large sludge particles, thereby producing a larger surface area for the microorganism to adsorb and ferment. This reduction in silt and dead organic matter can be reflected not only by better water quality but also by better sediment conditions.
Combination of bacteria and enzymes
In order to test the effect of the combination of beneficial bacteria and enzymes on the sediment under actual soil culture conditions, the listed products (2x109 CFU/g, Baidixiao, Austrian BIOMIN) are used, and the product contains a mixture of enzymes ( Amylase, xylanase, cellulase, protease) In the Zhuhai, China, field trials of Penaeus vannamei were conducted under intensive farming conditions.
The soil pond (10-12 mu/ton) has a water depth of 1 – 1.2 m, and the shrimp seedlings (about 1.4 g/shrimp) are stocked with a density of 50 shrimps per square. The test was carried out for 57 days. The probiotic product, Baishui Net, is used once every 5 days, and the dosage is 40 g/mu. The combination of probiotics and enzymes is used once a month for 33g/mu. Two shrimp ponds in the experimental group and the control group were completely consistent in feeding.
The results showed that the average daily weight gain of the shrimp in the experimental group (0.15 g/day) was 36% higher than that of the control group (0.11 g/day). The feed coefficient (FCR of 0.91) of the test group was improved by 8% compared to the control group (FCR of 0.99). In the photograph, the bottom sediment of the test group was yellow, while the sediment of the control group was dark black, indicating the accumulation of organic waste.
Application of test group shrimp pond bottom mud
Control group shrimp pond sediment
The results indicate that the combination of probiotics and enzymes converts the bottom of the pond containing black, colloidal organic sludge into a cleaner yellow sediment. For animals, enzymes improve growth and production performance by balancing the surrounding environment of the shrimp.
For ponds with higher aquaculture density and feeding rate, the water quality and substrate quality are more deteriorated during the aquaculture production process, and the effect of applying enzymes may be more obvious.
Application prospects
It is promising to improve the water environment under high-density culture conditions and to use the combination of probiotics and enzymes as an effective management tool. Enzymes act as biological control agents in pond culture, especially to improve water quality and substrate quality, as well as the production performance of farmed fish and shrimp.
Studies have shown that the use of probiotics and enzymes in culture ponds can improve the quality of the substrate and improve the performance of the shrimp. The addition of specific enzymes (protease, amylase, cellulase, xylanase) and/or enzyme-producing probiotics such as Bacillus, promotes the pre-digestion of certain complex nutrients and contributes to the release of digestible nutrients. This will help to reduce the accumulation of silt and organic matter, and also reduce the anaerobic conditions at the bottom of the pond, thereby improving the culture conditions of farmed fish and shrimp.
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