Biofloc Technology Research Articles

A Review: Microbes and Their Effect on Growth Performance of Litopenaeus vannamei (White Leg Shrimps) during Culture in Biofloc Technology System.

In the modern era of Aquaculture, biofloc technology (BFT) systems have attained crucial attention. This technology is used to reduce water renewal with the removal of nitrogen and to provide additional feed. In BFT, microorganisms play a crucial role due to their complex metabolic properties. Pathogens can be controlled through multiple mechanisms using probiotics, which can promote host development and enhance the quality of the culture environment. During culturing in a biofloc technology system, the supplementation of microalgae and its accompanying bacteria plays a beneficial role in reducing nitrogenous compounds. This enhances water quality and creates favorable environmental conditions for specific bacterial groups, while simultaneously reducing the dependency on carbon sources with higher content. The fluctuations in the bacterial communities of the intestine are closely associated with the severity of diseases related to shrimp and are used to evaluate the health status of shrimp. Overall, we will review the microbes associated with shrimp culture in BFT and their effects on shrimp growth. We will also examine the microbial impacts on the growth performance of L. vannamei in BFT, as well as the close relationship between probiotics and the intestinal microbes of L. vannamei.

A Review on Biofloc System Technology, History, Types, and Future Economical Perceptions in Aquaculture.

Given the scarcity of water and land resources, coupled with the competitive nature of aquaculture, the long-term viability of this industry will depend on strategies for vertical development. This involves enhancing production environments, increasing productivity, and advancing aquaculture technologies. The use of biofloc technology offers a potential solution to mitigate the adverse environmental impacts and the heavy reliance on fishmeal in the aquaculture sector. This method is designed to effectively assimilate inorganic nitrogen found in aquaculture wastewater, thereby enhancing water quality. Additionally, this process produces microbial protein, which can serve as a viable supplemental feed for aquatic animals. Furthermore, this technique has the potential to reduce the feed conversion ratio, thereby lowering overall production costs. This article provides an overview of the evolving field of biofloc system technology within aquaculture. In this study, we will examine the historical development and various types of biofloc systems, as well as the factors that influence their effectiveness. Finally, we will explore the economic potential of implementing biofloc systems in aquaculture.

A novel multitrophic biofloc technology for duckweed and Megalobrama amblycephala integrated culture: Improving nutrient utilization and animal welfare

Biofloc technology (BFT) is an eco-friendly aquaculture model that utilizes zero-exchange water. In this study, we investigated the integration of duckweed into BFT in an effort to enhance nitrogen, phosphorus, and carbon utilization and to improve animal welfare for cultivating Megalobrama amblycephala. The experiment spanned 75 days, comparing a group of M. amblycephala supplemented with duckweed (DM) to a control group (CG) with no supplementation, where duckweed consumption relied solely on the feeding behavior of the fish. The concentrations of nitrate, total nitrogen, and phosphorus accumulation were lower in the DM than in the CG from day 45 onwards, with differences of 16.19, 26.90, and 1.45 mg/L, respectively, at the end of the experiment. The DM showed simultaneous increases of 5.77, 11.20, and 5.07 % in the absolute utilization of nitrogen, phosphorus, and carbon, respectively. The abundance of TM7a (10.27 %), linked to nitrate absorption, became the dominant genus in the water of the DM. Additionally, the abundance of Cetobacterium, associated with carbohydrate digestion, was significantly higher in gut of the DM (23.83 %) than in the gut of CG (1.24 %, P < 0.05). Supplementing the diet of M. amblycephala with duckweed improved digestion and antioxidant enzyme activity. Transcriptome data showed that duckweed supplementation resulted in an increase in the expression of genes related to protein digestion and absorption and carbohydrate metabolism in M. amblycephala, and analysis of the significantly enriched pathways further supported improved antioxidant capacity. Based on the above results, we concluded that as M. amblycephala consumes more duckweed, the differences in nitrogen and phosphorus levels between the DM and CG would continue to increase, along with a simultaneous increase in fixed carbon. Thus, this study achieved the goal of recycling BFT resources and improving animal welfare by integrating duckweed.

A biofloc system avoids the adverse effects of diets with suboptimal protein levels on zootechnical performance, intestinal histomorphometry, and protein metabolism of Nile tilapia juvenile fed Spirulina biomass (Arthrospira platensis) as an alternative protein source.

This study aimed to evaluate the effect of the biofloc technology (BFT) system and the replacement of fish meal with Spirulina biomass on productive performance, intestinal histomorphometry, plasma biochemistry, and oxidative stress of Nile tilapia juveniles (Oreochromis niloticus) fed suboptimal levels of protein. Two factors were evaluated: production systems (clear water × BFT) and replacement of fish meal with Spirulina (0, 33, 66 e 100%). The design was in a 2 × 4 randomized factorial scheme with four replications, and the fish were evaluated for 48days. Four isoproteic (28% crude protein) diets were formulated with gross energy values close to 4300kcalkg-1. Nile tilapia juveniles (0.23 ± 0.01g) were distributed in 16 circular tanks (70 L) at seven fish/tank. The diets were formulated with protein levels approximately 20% below that required for the species and life stage. No interaction was observed between the factors evaluated (production systems × Spirulina inclusion). Rearing the fish in the BFT system avoided the adverse effects of diets with suboptimal protein levels on performance, intestinal histomorphometry, and protein metabolism. Lower values lower lipid peroxidation and higher antioxidant capacity were observed in fish reared in the BFT system, showing evidence of improvements in antioxidant responses and lower levels of physiological oxidative stress. Spirulina completely replaced fish meal in the diets of Nile tilapia juveniles without adverse effects on intestinal morphometry, protein metabolism, and antioxidant response. Replacing 66% of fish meal with Spirulina improved the productive performance, regardless of the rearing system.

Biological removal of nitrogenous waste compounds in the biofloc aquaculture system: a review

Abstract Aquaculture has experienced significant global expansion and is considered one of the fastest-growing sectors in food production. However, there exist additional challenges that restrict the capacity to achieve maximum efficiency in aquaculture systems, such as issues over water quality and shortages of appropriate live feeds. Intensive aquaculture systems involve the use of protein-rich prepared feed for feeding the cultured animals. This may give rise to the discharge of nitrogenous compounds into the water, which can pose a risk to the environment when present in excessive quantities beyond the acceptable levels. In recent years, an innovative method called biofloc technology (BFT) has become a practical solution to this issue. Undoubtedly, BFT offers a groundbreaking method for nutrient disposal that eradicates the requirement for excessive water use or equipment maintenance. Three primary types of microorganisms are crucial in alleviating the adverse impacts of nitrogen compounds in this technique. Photoautotrophs participate in the processes of removal and absorption, whereas chemoautotrophs promote nitrification and conversion. Heterotrophs contribute to the absorption process. Biofloc predominantly consists of heterotrophic bacteria, alongside algae, protozoa, rotifers, and nematodes. While there have been reviews carried out on multiple aspects of biofloc technology, there exists a lack of literature that tackles this particular field of research progress. This article discusses every aspect and techniques of biological management used for removing nitrogenous waste compounds in biofloc aquaculture systems.

Probing into the impacts of endogenous and exogenous short chain fatty acids (SCFAs) in fish health and growth

Abstract Short-chain fatty acids (SCFAs) are small organic acids exist in the fish gastrointestinal tract, mainly acetate, propionate, and butyrate. These SCFAs are produced through anaerobic fermentation of dietary non-digestible carbohydrates by gut microbes. Though enough studies have been devoted to showcasing the potential of SCFAs in human nutrition, the research on their production, potential, and existence in fish has been comparatively limited until recently. This review aims to provide a comprehensive overview of the current knowledge regarding SCFAs in aquaculture. It starts with commenting on the different sources, such as substrate and microbial species that are responsible for the production of SCFAs and their transportation and ends up depicting the relationship between biofloc technology and SCFAs production. This review also discusses the factors influencing SCFA production, such as environment, diet, and feeding habits of fish. Furthermore, the biological functions of SCFAs have been highlighted, and critical findings were compiled, including immunomodulatory effects, physiological response, gut health, and immunity.

Use of Bacillus subtilis multiplicate in the water used for biofloc formation: Growth, hemato-biochemistry, intestinal bacteria colonies, and bacterial resistance evaluations of Nile tilapia

Probiotics in the biofloc technology (BFT) system improve fish growth and immune response and promote a favorable intestinal microbiota balance. This study aimed to investigate the growth, hemato-biochemical parameters, bacterial resistance, and the number of intestinal bacteria colonies of Nile tilapia (6.23 g) reared in the BFT system with graded levels of Bacillus subtilis multiplicate (BSM) in the water. The multiplication of these microorganisms was performed in a biofactory. Fish were distributed into four different groups with graded BSM concentrations in the water of 0.00, 0.25, 0.50, and 0.75% (or 0; 750; 1500; and 2250 mL; called BSM0 (control), BSM25, BSM50, and BSM75, respectively). The experimental procedure had 45 days for growth performance evaluations and seven additional days of bacterial challenge with Aeromonas hydrophila. The experimental design was randomized into four treatments in triplicate (n = 20 fish per tank; initial stocking density of 0.50 kg m−3). Survival was 100% before and after the bacterial challenge. Increasing BSM in the BFT system had a positive linear effect on nitrite, nitrate, settled solids, hemoglobin, and hematimetric indices. BSM50 showed the highest specific growth rate, weight gain, intestinal total bacteria, and B. subtilis counts and the lowest feed conversion rate. In BSM50 and BSM75, liver glycogen levels and aspartate aminotransferase (AST) activity were higher and lower, respectively, than in the other treatments. Plasma total cholesterol, total proteins, albumin, and skin mucus total proteins and albumin were highest in BSM25. After the bacterial challenge, the number of lesions was lower in BSM75 than in the control group. In conclusion, we recommended BSM50 because it increased the growth performance and bacterial colonization in the intestine. It also decreased liver AST activity in Nile tilapia reared in the BFT system without compromising water quality and hematological and plasmatic parameters.

Metabolic and immune status of Pacific white shrimp Penaeus vannamei concerning farming conditions

Biomarkers for monitoring shrimp health have been proposed but scarcely evaluated at the farm level. We analyzed several indicators of energy status in shrimp under farming conditions concerning stocking densities (100 m-2 with biofloc, 15 and 7 m-2). The influence of the year's season (temperature) was also analyzed, and, finally, an unfortunate event of White spot syndrome virus (WSSV) infection occurred on the 7 m-2 farms, adding another condition. At shrimp sampling from ponds, the effect of acute handling stress was also analyzed for indicators typically affected by such procedure with a 3- and 10-fold increase in glucose and lactate levels in hemolymph, respectively, regardless of density. This response was partially blunted at lower temperatures and WSSV incidence. Increased levels of protein in the hepatopancreas, adenylic energy charge (AEC) in both hepatopancreas and muscle and phosphagens in muscle were observed in shrimp from the 100 m-2 farms, suggesting a better nutritional and energetic status in shrimp cultured at high density with biofloc technology. Shrimp with WSSV presented lower hemocyanin levels in hemolymph, most likely associated with its role in the immune response. In WSSV-infected shrimp, the stress response regarding glucose increase was blunted, whereas a stress-induced increase in triglycerides (TG) levels in hemolymph was observed only with WSSV. Increased TG levels in those shrimp hepatopancreas could indicate a switch from carbohydrate to lipid-based metabolism associated with the preferential use of carbohydrates (Warburg effect) for virus replication in the early infection state.

Pengembangan Integrasi Budidaya Ikan Lele Dan Tanaman Herbal Di UPR Doa Mandeh

The catfish cultivation business carried out by UPR Doa Mandeh since 2015 still requires support in the form of assistance and training for its development. Meanwhile, the availability of fish seeds in South Sumatra is still very dependent on other regions, such as Lampung, Jambi and West Java. The lack of use of appropriate catfish cultivation technology and the use of commercial feed has an impact on the low production of fish seeds produced. Apart from that, there has been no effort to treat waste water which has the potential to have a negative impact on the surrounding environment. For this reason, community service (PPM) is carried out, which applies lecture materials, research and publications that have been carried out by the proposing team in the form of application of biofloc technology, making liquid fertilizer and cultivating herbal plants. The aim and benefits of carrying out this activity are to develop the catfish cultivation business, increase seed production, utilize waste water from catfish rearing media into liquid fertilizer products that can be used to develop herbal plant cultivation which will ultimately increase the income of cultivators at UPR Doa Mandeh. The activity model is in the form of empowerment, development and assistance which is implemented using counseling, training and technical/production assistance methods. The results of this activity are high survival and growth rates for catfish, water quality is in the optimal range, and the richness of nutrients in wastewater from the biofloc system can be used as liquid fertilizer for herbal plants. Keywords: biofloc; catfish; herbal plants; liquid fertilizer

Effects of Commercial Probiotics on the Growth Performance, Intestinal Microbiota and Intestinal Histomorphology of Nile Tilapia (Oreochromis niloticus) Reared in Biofloc Technology (BFT).

Though different types of commercial probiotics are supplemented in biofloc technology (BFT), very little information is available on their effects on the farmed fish. Therefore, this study focused on evaluating the effects of three most commonly used commercial probiotics on the growth performance, intestinal histomorphology, and intestinal microbiota of Nile tilapia (Oreochromis niloticus) reared in BFT. Tilapia fry, with an average weight of 3.02 ± 0.50 g, were stocked at a density of 60 fry/0.2 m3, and cultured for 90 days. Three commercial probiotics were administered, with three replications for each: a single-genus multi-species probiotic (Bacillus spp.) (T1), a multi-genus multi-species probiotic (Bacillus sp., Lactobacillus sp., Nitrosomonas sp., Nitrobacter sp.) (T2), and a multi-species probiotic (Bacillus spp.) combined with enzymes including amylase, protease, cellulase, and xylanase (T3). The results showed significant variations in growth and feed utilization, with T3 outperforming other treatments in terms of weight gain, liver weight, and intestine weight. Adding Bacillus spp. with enzymes (T3) to water significantly increased the histomorphological parameters (villi length, villi depth, crypt depth, muscle thickness, intestinal thickness) as well as microbes (total viable count and total lactic acid bacteria) of intestine of fish compared to T1 and T2, leading to improved digestion and absorption responses. It is concluded that the supplementation of commercial probiotics has potential benefits on farmed fish species in BFT.

Cumulative mortalities in white leg shrimp, Litopenaeus vannamei Boone 1931, cultured in biofloc system in Egypt reflected new record of Fusarium verticillioides infection

The Egyptian aquaculture sector is still struggling to establish L. vannamei culture. In an effort to stimulate shrimp production with minimal environmental impact and less water loss, biofloc technology (BFT) has been employed. Chronic mortality was recently observed in L. vannamei which was raised in the BFT system. Examining samples of moribund shrimp revealed sporadic melanization on the musculature and gills, suggesting the potential existence of black gill disease. The present work was carried out to isolate and identify potentially implicated fungus species based on mycological properties of interest. To isolate and serve as initial identification tools, wet mount preparations and colonial features, along with slide culture techniques, were used. PCR assays, gene sequencing, and phylogenetic analyses were used in the molecular identification process to clarify the confirmation of the fungal isolates that were acquired. The pathogenicity tests were designed to fulfil Koch’s postulates in addition to clarifying the infectivity of isolated fungus. Moreover, histopathological examination was employed to notice tissues’ alterations associated with experimentally infected shrimp. The results revealed the isolation of three fungal isolates, namely, BNS 1117, BNS 2117, and BNS 3117, that were confirmatively identified as Fusarium verticillioides, and their selected sequences were submitted to Genbank. Moreover, experimental infection using F. verticillioides selected isolate (BNS 31,117) at both high (5 × 105 CFU/mL, group A) and low (3 × 105 CFU/mL, group B) doses of its conidial suspensions experienced cumulative mortality of 72.2% and 21.1%, respectively. Besides, the selected isolate was re-isolated from the experimentally infected shrimp in a pure form, which satisfied Koch’s postulates. Histopathological alterations demonstrated several degrees of either degenerative, oedema, or proliferative changes in the hepatopancreas, musculatures, and gills, respectively. This study sets a new record for F. verticillioides to be included in Fusarium species linked to shrimp mortality.

Enhancing Indoor Culture of Weather Loach (Misgurnus anguillicaudatus) and Caipira Lettuce (Lactuca sativa) in a Decoupled FLOCponics System

Interest in aquaponics (AP) is increasing due to its ability to minimize sewage and maximize feed efficiency in fish farming. However, owing to limitations of intensive cultures and a lack of nutrients such as NO3 for growing crops, AP requires the use of artificial nutrients. Therefore, novel approaches are required to develop AP-intensive culturing methods. An AP system based on biofloc technology (BFT) called FLOCponics (FP) has been recommended. Here, the productivity of the weather loach (Misgurnus anguillicaudatus) in the FP system, BFT system, and flow-through systems (FTSs), as well as these systems’ effect on Caipira lettuce (Lactuca sativa) growth, was analyzed. To compare crop productivity, a hydroponic (HP) bed was installed. The growth rate of M. anguillicaudatus showed significant differences, at 51.1 ± 3.69% in the FP system, followed by 24.0 ± 4.16% in the BFT system and −14.3 ± 1.4% in the FTS. Its survival rates were better in the FP system (91.1 ± 2.64%) than in the BFT system (82.1 ± 10.98%) or the FTS (66.8 ± 2.75%) (p &lt; 0.05). Total ammonia nitrogen and NO2−-N concentrations were stabilized in every plot during the experimental period. However, the NO3−-N concentration continuously increased in the BFT system but decreased in the FP system and was maintained. The shoot weight of the Caipira lettuce was 163.6 ± 8.65 g in the FP system and 149.6 ± 9.05 g in the HP system. In conclusion, FP system can provide a large amount of nutrients and improve the growth performance of both fish and crops in the FP system.

Biofloc technology in aquaculture: Advantages and disadvantages from social and applicability perspectives – a review

Abstract The world aquaculture industry seeks sustainable production strategies to respond to the needs of the growing world population for valuable food. Biofloc technology (BFT) is accepted as a novel sustainable method that reduces the pollution load on receiving water resources with its zero-water-discharge approach, eliminates extra water treatment costs with its biological cycles, and supports the growth performance of reared animals and thereby reduces feed costs. However, each BFT system has its own set of difficulties and obstacles. This review focuses on the advantages and disadvantages of BFT systems in terms of economy, sociability and applicability. The BFT shows more effective results in the conversion of toxic nitrogenous compounds to nontoxic compounds compared with the technologies based on nitrification processes. In addition, the growth performance and health of the cultured animals are generally better in BFT systems than those in conventional rearing systems (continuous water flow). The risk of common diseases occurrence due to pathogenic microorganisms appears to be lower in BFT systems compared to conventional aquaculture. It is also noteworthy that the immune system, biochemical stress indicators and antioxidant activities of organisms held in BFT systems are positively affected. In BFT systems based on microbial activity, the high water temperature demanded by bacteria is a limiter for the system. Moreover, a higher aeration/energy requirement is the case in BFT to meet the oxygen demand of all organisms including fish, shrimp, heterotrophic bacteria, nematodes, rotifers and others inside. There is also another concern about the acceptability potential of the cultured organism in BFT systems for consumption. Finally, since the high temperature demand of the system will create high energy costs, it should be considered as another restriction that forces the application. Considering the advantages and disadvantages of BFT systems as sustainable aquaculture, this review provides a guide for future studies and full-scale implementations.

Carbohydrate addition strategy affects nitrogen dynamics, budget and utilization, and its microbial mechanisms in biofloc-based Penaeus vannamei culture

Biofloc technology (BFT) is a microbial biotechnology that has shown great potential in water quality control and nutrient re-utilization towards sustainable aquaculture. Carbohydrate addition is the main operation means for the application of BFT; however, we are still unclear how it affects microbial-driven nitrogen (N) transformation and utilization in BFT systems. In this study, autotrophic- and heterotrophic-dominated BFT systems (AS vs. HS) in triplicates were operated by two molasses addition strategies for a 13-week production trial of P. vannamei. Throughout the trial, more amount of bioflocs (in terms of VSS) were produced in HS than in AS. Higher concentrations of NH4+-N, NO2−-N, NO3−-N, TIN and TN while lower concentrations of TON were monitored in AS compared to HS. N budget analysis showed that the harvested shrimp deposited >34.4% of input N; and higher N retention in the final culture water while lower N loss and N discharge from the systems were found in AS compared to HS. Higher efficiencies of gross and feed N utilization were achieved in HS (36.6% and 38.8%) than in AS (34.5% and 34.9%). Metagenomic analysis revealed that abundant and diverse N-cycling microbial communities and functional genes in bioflocs constituted a complete and complex N-cycling network, which was the driving force of N transformation and recycling in the culture water of systems. The lower abundances of nitrifying bacteria and associated genes led to the inhibition of nitrification under high molasses addition in HS, which accounted for the differences in N dynamics, budget and utilization efficiency between AS and HS. Together, a quantitative model of N migration and transformation driven by N-cycling microbial communities of bioflocs was depicted in closed BFT systems for shrimp aquaculture. This study firstly revealed the N-cycling microbiome and functional effects in BFT systems, which provides theoretical and technical foundations for efficient N management in intensive aquaculture.

Strategies for promoting sustainable aquaculture in arid and semi-arid areas – A review

Abstract Starvation and malnutrition are one of the most destructive problems faced by the poor and needy in the world. With the world population expected to increase by 9.7 billion by 2050, there are growing concerns about the long-term sustainability of many existing food production systems to meet future needs for food. Aquaculture is one of the important sources of food supply, the development of which is of great importance as an important weapon in the global fight against malnutrition and poverty, especially in developing countries and arid and semi-arid regions of the world. In recent decades, aquaculture has dominated all sectors of livestock production in terms of growth and increasingly contributes to food security, poverty reduction, job creation and sources of income. It is important to follow sustainable development goals to increase aquaculture production. Climate change is currently affecting food security through increasing temperature and decreasing rainfall, especially in arid and semi-arid regions. Food security is a global concern and access to affordable, nutritious, safe and properly cultivated food is one of the most important issues globally. The main emphasis in the development of aquaculture in arid and semi-arid areas is the use of new technologies based on water saving, such as biofloc technology (BFT), integrated multi-trophic aquaculture system (IMTA) and recirculating aquaculture systems (RAS). In this study, the importance of aquaculture as a sustainable source of food production in arid and semi-arid regions is discussed.

Impact of Organic Carbons Addition on the Enrichment Culture of Nitrifying Biofloc from Aquaculture Water: Process, Efficiency, and Microbial Community.

In this study, we developed a rapid and effective method for enriching the culture of nitrifying bioflocs (NBF) from aquacultural brackish water. The self-designed mixotrophic mediums with a single or mixed addition of sodium acetate, sodium citrate, and sucrose were used to investigate the enrichment process and nitrification efficiency of NBF in small-scale reactors. The results showed that NBF with an MLVSSs from 1170.4 mg L-1 to 2588.0 mg L-1 were successfully enriched in a period of less than 16 days. The citrate group performed the fastest enrichment time of 10 days, while the sucrose group had the highest biomass of 2588.0 ± 384.7 mg L-1. In situ testing showed that the highest nitrification efficiency was achieved in the citrate group, with an ammonia oxidation rate of 1.45 ± 0.34 mg N L-1 h-1, a net nitrification rate of 2.02 ± 0.20 mg N L-1 h-1, and a specific nitrification rate of 0.72 ± 0.14 mg N g-1 h-1. Metagenomic sequencing revealed that Nitrosomonas (0.0~1.0%) and Nitrobacter (10.1~26.5%) were dominant genera for AOB and NOB, respectively, both of which had the highest relative abundances in the citrate group. Linear regression analysis further demonstrated significantly positive linear relations between nitrification efficiencies and nitrifying bacterial genera and gene abundance in NBF. The results of this study provide an efficient enrichment culture method of NBF for the operation of biofloc technology aquaculture systems, which will further promote its wide application in modern intensive aquaculture.

Monoculture and Mixed Culture of Pacific White Shrimp Litopenaeus vannamei and Tiger Shrimp Penaeus monodon in Biofloc System: A Comparative Study

The microbial modification method known as Biofloc Technology (BFT) has been used regularly in prawn culture operations lately. The primary component of BFT culture systems, microbial Biofloc, is responsible for improving water quality, supplementing natural nutrition, and encouraging the growth and welfare of grown prawns. An attempt has been made to investigate the effects of adding probiotics (Bacillus licheniformis and Lactobacillus rhamnosus) and the Biofloc system on water quality parameters and the performance of shrimp Litopenaeus vannamei and Penaeus monodon. Various external carbon sources, such as molasses and tapioca flour combinations, were used for the development of Bioflocs in the present study both under monoculture and mixed culture operations. Experimental diets comprising one control, one supplemented with probiotics and bioflocs (combinations of tapioca flour and molasses developed with varying external carbon sources), and both monoculture and mixed culture operations of Litopenaeus vannamei and Penaeus monodon were used in feeding trail experiments for about 120 days. Because mixtures of both Probiotics and Bioflocs were added, all the water quality indicators remained in optimal condition and provided resistance and protection against Candidate species of cultivation. Along with acting as a food supplement for prawns, intense mechanical aeration also promotes the microbial community's breakdown of toxic nitrogen and other pollutants. Productivity rates increased dramatically as a result. Therefore, BFT is an effective pathogen replacement, preserves ideal water quality, and boosts the growth and survival of prawns from L. vannamei and P. monodon. Probiotics and Bioflocs are used in combination in this work to maintain good water quality metrics and P. monodon and L. vannamei growth performance.

Determination of acute toxicity and evaluation of the chronic effect of nitrate on compensatory growth of Litopenaeus vannamei reared in a biofloc technology system

Understanding the effect of acute and chronic nitrate stress on Litopenaeus vannamei grown in intensive biofloc technology systems is essential for production optimization. The present study evaluated L. vannamei exposed to nitrate extremes at a salinity of 25 g.L−1 measuring survival and possible recovery through compensatory growth. An initial clear-water lethal test, revealed an LC50–96 h for nitrate of 2789.11 mg.L−1. The nitrate safe level was determined as 278.91 mg.L−1by the Sprague Factor (0.1 of the LC50–96 h). Consequently, a chronic exposure experiment was carried out in a Biofloc Technology System. A 3 × 2 experimental design was applied, with two nitrate concentrations (278.91 mg.L−1 and 139.45 mg.L−1) and three “stress” exposure times (10, 20 and 30 days) followed by 48, 38 and 28 days “recovery” time, respectively. A control, in which the nitrate was maintained below 25% of the calculated safe level was maintained for 58 days. The experiment was divided into two phases: (1) stress and (2) recovery. Survival did not differ among treatments during the experimental period. Shrimp exposed to concentrations of 278.91 mg.L−1 and 139.45 mg.L−1of nitrate over 20 and 30 days exhibited reduced growth, while growth of shrimp exposed 10 days did not differ from the control. After the end of the recovery phase (day 58), no significant differences were found in shrimp weights among treatments. Results indicate L. vannamei presents higher resistance to nitrate, but prolonged exposures (>20 days) to concentrations above 139.45 mg.L−1may negatively affect growth rates. However, when lower nitrate values are re-established, the animals exhibit compensatory growth nullifying significant differences to cohort members maintained at optimal nitrate throughout.

The effect of using nano and microbubbles as aeration strategies on the nitrification process, microbial community composition, and growth of Penaeus vannamei in a super-intensive biofloc system

The aim of this study was to evaluate the effect of using nano and microbubbles as aeration strategies on the nitrification process, microbial community composition of water and biofilm, microbial flocs proximate composition, and growth of Penaeus vannamei in a pilot scale super-intensive system with biofloc technology. A grow-out (stocking density: 450 shrimp m−3) was carried out for 74 days in a greenhouse with nine 35 m3 tanks, using the following treatments: T1: nanobubbles, T2: microbubbles, T3: mixed (nano + microbubbles). The nanobubbles were generated by nozzle-type air injectors and the microbubbles were generated by microperforated hoses. Artificial substrates, with an area equivalent to 200% of the lateral surface, were used into the experimental units. Molasses was used as an organic carbon source at a carbon:nitrogen ratio of 15:1. The main morphotypes of bacteria in the water and in the biofilm were analyzed using direct counting and a profile of the bacterial composition of the water was performed using metagenomic analysis. Control of total ammonia nitrogen (TAN) was better in treatments T2 and T3 than in T1. At the end of the experiment, treatment T3 showed a higher total abundance of bacteria in the water than T1 and T2. Bacillus abundance in the biofilm was higher in the T3 treatment than in T1 and T2. The relative abundance of nitrifying bacteria was <1% in all treatments. Treatment T1 had a higher relative abundance of nitrite-oxidizing bacteria than the others. However, the T3 treatment had a better distribution of nitrifying bacteria species. T3 treatment showed a higher diversity and evenness of operational taxonomic units. The microbial flocs in the T2 had a higher crude protein content than in the T1. These results indicate that the use of a mixed aeration system promotes a higher load of microorganisms, which has proven to improve water quality and can influence shrimp growth. The shrimp final weight was higher in T1 (12.57 g) and T3 (12.54 g) than in T2 (11.70 g), survival was higher in T3 (97.17%) than in T1 (80.33%), and yield was higher in T3 (4.61 Kg m−3) than in T1 (4.06 Kg m−3) and T2 (4.21 Kg m−3). The treatment that used nano and microbubble as aeration strategy (T3) proved to be the best as it provided better TAN control, higher abundance of bacillus bacteria in the biofilm, higher diversity and evenness of bacteria, and even higher shrimp growth and survival.

Construction of suspended bagasse bioflocs and evaluation of their effectiveness in shrimp (Penaeus vannamei) aquaculture systems

This experiment was carried out to improve the operability of bioflocs technology and to better the application of bagasse, a sugarcane by-product or fibrous pulp of other plant materials, in aquaculture. Firstly, a generator device for suspended-bagasse was designed, and indigenous efficient nitrogen-reducing bacteria were screened and combined. Then a suspended-bagasse bioflocs Penaeus vannamei (initial body weight of 0.78 ± 0.33 g, density of 350 shrimp/m2) culture system was constructed with bagasse and indigenous probiotics (single probiotic or composite probiotic from the previous step) as components through the generator device. The commercial shrimp culture model with commercial probiotics applied was used as a control group with three replicates in each group. The experiment lasted for 50 days. The effects of suspended-bagasse bioflocs on the water quality, shrimp growth, and immune response in the shrimp culture system were evaluated. All experimental results were analyzed using one-way variance or linear estimation. The suspended-bagasse generator could promote rapid biofilm formation on the surface of the bagasse, and the hydraulic retention parameter can be set to 12 h. Besides, three efficient nitrogen-reducing strains were screened and identified (Halomonas alkalihila AC3–2, Rugerella sp BD15–5, and Halomonas venusta BD15–8). They were non-hemolytic, sensitive to most antibiotics, and non-pathogenic to shrimp. Their combination with Bacillus megaterium BZ5 (a previously isolated probiotic) in a 1:1:1:1 ratio resulted in the highest degradation efficiencies of 97.1% and 51.4% for ammonia and nitrite nitrogen, respectively. Furthermore, application experiments in shrimp aquaculture systems showed that suspended-bagasse flocs (with single bacteria and combined bacteria) reduced ammonia and nitrite nitrogen levels and promoted nitrification in the water of the shrimp aquaculture system. This suspended bagasse floc (with combined bacteria) system reduced water usage by 37.6% per kg of shrimp produced compared to the common culture system. Moreover, the suspended-bagasse flocs (with combined bacteria) improved hepatopancreatic digestive enzyme (trypsin, lipase, and α-amylase) and serum immune-related enzyme (lysozyme and phenol-oxidase) activity. This study indicates that it is feasible to cultivate suspended-bagasse flocs in shrimp aquaculture systems using a generator device with bagasse and probiotic bacteria as components. The flocs based on bagasse and indigenous complex bacteria can effectively reduce water exchange during shrimp aquaculture and improve shrimp production. Imperfectly, the microbial community and function of the biofilm on the surface of bagasse, which is very important for the interpretation of water quality variations, was not revealed in this experiment and needs to be refined in future work. Additionally, it is also worthwhile to evaluate the effectiveness of this device in other aquatic animal culture systems.