Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Fisheries submitted time 2022-05-18
Abstract：
[Objective] Bacillusis very useful to nitrogen conversion in water with low nutrition level, such as aquaculture waterbody. And this process generally affected by many factors, among which the characteristics of both factors of Bacillusstrains and environments are the most important ones. However, few researches could be obtained in regard to the comprehensive effects of those two aspects.
[Methods] Thus, in the present study, hydrolytic and bacteriostatic activities of two Bacullisstrains NT9 and YB3 were determined by using plate methods. Thereafter, four low-nutrition-level water conditions were prepared artificially, and the effects of characteristics of Bacillusstrains and environments on bacterial growth and nitrogen conversion were researched simultaneously, by separating out the total, direct and indirect effects of both aspects were with path analysis method.
[Results] Results showed that unlike B. cereusstrain YB3, strain NT9 was a B.subtilispossessed stronger proteolytic, amylolytic and bacteriostatic activities but with a weaker cellulase activity. However, as similar as strain YB3, strain NT9 could degrade organic nitrogen and ammonia, with a high of the ammonia-conversion rate of 89.3% under low nutrition condition. Results from path analysis showed that in models the main goodness-of-fit indices were all suitable, with high determination coefficients (R2) of 0.55-0.95. The cellulase activity (cel) of Bacillusstrains displayed significant direct positive effects on bacterial growth (gro) and degradations of organic nitrogen and ammonia (dtan) in most of the four water conditions (P<0.001). The environmental factors, such as the initial bacterial counts (iod), organic nitrogen content (ion), ammonia content (itann) and time duration phase (stage) also executed significant direct positive effects on groand dtan(P<0.05), but only for some special conditions. There were interactions among Bacillusactivities and environmental factors, which produced indirect effects on groand dtan, and in turn reinforced or weakened their direct effects, resulting in final significant (P<0.05) or non-significant (P>0.05) total effects of factors. Meanwhile, in some environments, groand dtancould significantly and directly improved each other (P<0.001), or produced indirect effects on each other.
[Conclusions] In conclusion, the characteristics of strain and environment could intensively affect the growth and nitrogen conversion of Bacillus,with different pattern in different water conditions, indicating that for better application of Bacillus, strategies should be made and adjusted according to water conditions, such as dosages and durations of strain and nitrogen sources.
Peer Review Status:
Awaiting Review
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Fisheries submitted time 2022-05-18
Abstract：
[Objective]For investigating the effects of biofloc technology (BFT) on commercial culture of adult Litopenaeus vannameishrimp [Methods] as well as environment in inland freshwater with low salinity, the growth performances of shrimp, water quality parameters, economic and environmental benefits were measured for both BFT and control system, by using 200 liters water with a salinity of 5‰ at a density of 90 shrimp per m3 in the present study.
[Results] Results showed that after a 63-days culture, the survival rate (100%) and productivity (1.32 kg/m3) of shrimp from BFT system were significantly higher than those of control system, respectively (P<0.05). And other growth performance indices, such as the average individual weight (13.20±1.64 g), special growth rate (4.26±0.20%/d) and feed conversion ratio (1.09±0.14) were also all higher in BFT system compare to control (P>0.05).
[Conclusions] In conclusion, application of BFT in inland culture of L. vannamei under low salinity condition not only elevated survival rate, improve growth and reduce FCR of shrimp.
Peer Review Status:Awaiting Review
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Fisheries submitted time 2022-05-17
Abstract：
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[Objective] To research effects of strain characteristics and water conditions on nitrogen conversion of Bacillusin aquaculture.
[Methods]Hydrolases activities, bacteriostatic activities and growth ability under oligotrophic condition of two Bacullisstrains NT9 and YB3 were determined. Thereafter, their nitrogen conversion effects in a simulating experiment for aquaculture were studied with path analysis method.
[Results] Results showed that strain NT9 was a strain of Bacullissubtiliswith a ammonia-degrading rate of 89.3% under oligotrophic condition with NH4Cl as unique nitrogen source, it had stronger protease-, amylase- and bacteriostatic-activities, but grew more slowly in the oligotrophic broth when compare to strain YB3. In the simulating aquaculture water bodies, both strain NT9 and YB3 did not obviously affect the dissolved oxygen, pH, alkalinity, concentrations of nitrite and nitrate, but promoted degradation of organic nitrogen which led to significant accumulation of ammonia (P< 0.05). However, the ammonia was not converted efficiently by both strains. Results of path analysis showed that the count of bacteria (cfu) in water was the main factor for organic degradation, with a path coefficient (direct effect) of 0.550 (P< 0.01), beside which the indirect effects of cellulose (cel) and growth ability (gro) through cfu were also important. Meanwhile, the main factor for ammonia conversion was growth and proliferation of bacteria (count increment, dcfu) which path coefficient was -0.112 (P< 0.01).
[Conclusions] In conclusion, in simulating aquaculture condition, both Bacillus strain NT9 and YB3 improved the degradation of organic nitrogen dramatically, but could not convert the ammonia efficiently. According to the results of path analysis, however, it could carry out a further research on synchronous conversion of ammonia by improving the growth of I strain in aquaculture water.
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Peer Review Status:Awaiting Review
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