Biofloc Composition Research Articles

Biofloc Technology in Improving Shellfish Aquaculture Production – A Review

Abstract Biofloc technology is instrumental in improving growth performance and yield in shellfish aquaculture, while leading to enhanced water quality through maintaining the nutrients level within a safe range. More specifically, toxic nitrogenous wastes are converted into beneficial microbial biomass known as “biofloc”, contributing to improve shellfish immune system. Among the various parameters affecting the efficiency of the process is the carbon source and C:N ratio. In light of these, the present work critically reviews the effects of biofloc systems on growth performance, immunity and diseases resistance in shellfish production. Moreover, it scrutinizes the microbial diversity and nutritional composition of biofloc. Then, the application of the technology in various shellfish cultures, including shrimp, freshwater prawn, crabs, crayfish, clam, and oyster, is presented. Overall, biofloc systems contribute to enhanced shellfish survival rate to the highest value of 96–100% for marine shrimp, 95–99% for freshwater prawn, 70–83% for crayfish, 83–100% for oyster, Crassostrea sp. and up to 2% for mud crabs larvae through substantially reducing the ammonia level in the culture (summarized in Table 1 – Table 5). Finally, the main challenges in utilizing biofloc systems, i.e., suitable aeration and mixing and microbial mechanisms involved are also explained to shed light on future research directions in the field.

Contribution of the diatom Navicula sp. to the growth of Penaeus vannamei post-larvae in biofloc system: a quantitative stable isotope assessment

ABSTRACT The addition of Navicula sp. to shrimp nurseries can improve the growth of Penaeus vannamei reared in biofloc systems. However, the contribution of microalgae to the biofloc formation and the effective contribution to shrimp nutrition remain unknown. In this study, Navicula sp. was added to biofloc nursery systems of P. vannamei at distinct time frequencies for evaluating its nutritional contribution to shrimp growth. Nursery rearing was carried out in bioflocs for 35 days at a stocking density of 3000 post-larvae m−3. Shrimp were fed using a commercial feed plus fresh culture of Navicula sp. at different frequencies: no addition of Navicula sp. (WN – control), the addition of 10 × 104 cells mL−1 of the diatom every 5, 10 and 15 days (N5, N10 and N15, respectively). Food sources relative contribution to P. vannamei development was estimated using a Bayesian mixture model. The isotopic discrimination factor (Δ15N and Δ13C) for each food source was determined experimentally. After 35 days of culture, survival (∼93 %) was similar across all treatments but there was a significant difference in weight gain and feed conversion ratio. The N10 treatment (0.50 ± 0.05 g, 0.99 ± 0.01) exhibited better growth parameters when compared to the WN treatment (0.33 ± 0.07 g, 11.46 ± 0.30). Biofloc was the food source most assimilated by shrimp followed by Navicula sp. and commercial feed. Contribution of Navicula sp. was higher in the N5 treatment. In the treatments with diatom addition, an inverse correlation was observed between the relative contributions of biofloc and Navicula sp., indicating that Navicula sp. is not in the biofloc composition, but it is directly consumed by P. vannamei post-larvae. Biofloc and Navicula sp. exhibited larger contributions to the growth of shrimp, reinforcing the importance of natural food sources to the aquaculture of P. vannamei post-larvae.

Integrated biofloc technology in red tilapia aquaculture: Salinity-dependent effects on water quality, parental stock physiology, reproduction, and immune responses

The study examines the impact of integrated biofloc technology (BFT), different salinity levels, and their combined effects over 90 days on various physiological parameters. The investigation includes growth performance and feed utilization, water quality, the chemical composition of biofloc and fish, digestive enzymes, reproductive performance, stress and biochemical indicators, and antioxidant-immune responses in red tilapia (Oreochromis spp.) broodstock. The fish were initially weighed (males: n = 270; 104 ± 0.96 g; females: n = 270; 93.2 ± 0.66 g) and subsequently divided into 12 treatment groups (6 for males and 6 for females) spread across 36 separate tanks (3 tanks per treatment; 45 fish per treatment; 15 fish/tank). The treatments involved three salinity levels (18, 28, and 36 ppt) in both clear water (CW) and BFT systems. The outcomes demonstrated that fish in the 36 ppt salinity with BFT treatment demonstrated significant improvements (P < 0.05) in growth parameters (final body weight, weight gain, and specific growth rate, feed intake, and feed conversion ratio). The condition factor in BFT groups increased in all salinity situations. The survival rates of broodstock were consistently high in all experimental conditions The study found that BFT and salinity significantly impacted (P < 0.05) whole body contents (moisture, protein, lipid, and ash) in both males and females. Water quality parameters showed variations between BFT and CW, with notable impacts (P < 0.05) on dissolved oxygen and pH. The BFT and salinity influenced digestive enzyme activities (protease, amylase, and lipase) and reproductive performance (males) and the 36 ppt salinity with BFT recorded the highest values. The hemato-biochemical and antioxidant-immune responses were also impacted by BFT and salinity exposure. The study highlights the potential benefits of incorporating BFT into red tilapia aquaculture systems, particularly in optimizing growth, health, and reproductive performance under various salinity conditions, which can enhance sustainable intensification, disease control, and environmental stewardship.

Light Limitation Alters Water Quality, Biofloc Composition, Zooplankton Community, and Performance of the Whiteleg Shrimp (Litopenaeus vannamei) Reared with Intensive Biofloc

Light Limitation Alters Water Quality, Biofloc Composition, Zooplankton Community, and Performance of the Whiteleg Shrimp (Litopenaeus vannamei) Reared with Intensive Biofloc

Impact of the co-cultivation of macroalgae (Ulva lactuca f. fasciata) on the composition of biofloc in a zero water exchange system used for rearing Pacific white shrimp (Litopenaeus vannamei) (Decapoda, Dendrobranchiata)

Abstract In a closed, or zero water exchange, greenhouse aquaculture system, this study examined the interaction between the aggregation flocs in the mono- and co-cultivation of Pasific white shrimp, Litopenaeus vannamei (300 individuals/m3) with macroalgae, Ulva lactuca f. fasciata at different densities of Ulva (1, 2 and 3 g/l). The investigation was conducted under zero water exchange conditions. The accumulated flocs were compared between the various treatment groups: without Ulva (Treatment Control Group), Ulva at 1 g/l density (T1: Treatment 1), Ulva at 2 g/l (T2: Treatment 2), and Ulva at 3 g/l (T3: Treatment 3). Ultimately, it was determined that Ulva cultivation using the Biofloc system actually helped to ensure the water quality in the zero water exchange culture system during the 35-day experimental period with reduced cyanophyte densities, that can cause toxic algal blooms in aquaculture systems. This was interpreted to result from the fact that Ulva is a naturally occurring bioremediation agent.

Potential benefits of Bacillus subtilis-mediated bioflocs in supplementary feeding on triangle sail mussels Hyriopsis cumingii: a pilot study of fluorescence-labeled floc-forming bacteria

As micro-particle aggregates, bioflocs may be potential baits for ingestion by triangle sail mussels and supplementary feeding raises more concerns. Besides, a plasmid carrying the green fluorescent protein (GFP) gene was transformed into floc-forming Bacillus subtilis (GFP-B. subtilis) to visualize its colonization during the bioflocs ingestion. To investigate the potential benefits of bioflocs on H. cumingii, Chlorella vulgaris diets were supplemented with nothing (control group, CG) or bioflocs accounting for the microalgae biomass at 25% (T1), 50% (T2), and 100% (T3) respectively. The community composition of bioflocs was analyzed and some species like phylum Proteobacteria, order Rhodobacterales and genus Paracoccus with potentials to improve water quality were found. Furthermore, supplementary bioflocs could reduce the concentrations of inorganic nitrogen in the aquacultural environment. Differences in growth traits across all groups were insignificant, but the digestion, metabolic and immune response of H. cumingii were promoted remarkably. Interestingly, some colonies of GFP-B. subtilis were detected in the intestines of H. cumingii from T1, suggesting H. cumingii could uptake bioflocs efficiently and intestinal colonization of B. subtilis might be accomplished. Besides, supplementary bioflocs with the highest ratio (T3) could improve the physiological status of organs and suppress the dominance of potential pathogens such as Aeromonas and Pseudomonas. It was assumed that B. subtilis might stimulate the healthy intestine development via intestinal colonization. Overall, B. subtilis-mediated bioflocs is beneficial to H. cumingii and more feeding strategies of bioflocs in H. cumingii farming are expected to be developed in future.

A Qualitative and Biochemical Analysis of Biofloc from an Indoor Biofloc Technology System Culturing Oreochromis Karongae

The structure of microbial communities in a Biofloc Technology (BFT) system has a great influence on the optimal functioning of the system. This makes understanding the microbial composition in BFT of paramount importance. A study was conducted to characterize the microorganisms in an indoor biofloc technology system. The microorganisms were qualitatively and biochemically analyzed. Qualitative analysis of microorganisms in BFT was carried out using microscopy and plate culture of bacteria and fungi. Isolated bacteria were identified by colony morphology, gram staining and microscopic observation. Catalase test, as a biochemical test, was also used in identifying bacteria. Biochemical analysis of the bio floc was achieved through proximate analysis of nutrients following AOAC (2002) methods. The bio floc sample used in the present study was obtained from culture water of three 1000l circular fibreglass tanks with a working volume of 580l of bio floc water per tank. Oreochromis karongae fingerlings were stocked in the three tanks at a stocking density of 6kg/m3 per tank and cultured for 12 weeks. The fish were fed 30% CP on-farm formulated feed (2mm pelleted) with a feeding rate of 1.5% of the total estimated fish biomass. Maize flour was added in tanks to maintain an optimum C/N ratio (above 10) for heterotrophic bacteria production. Microscopy of the biofloc water revealed various types of microorganisms, which included Protozoa (e.g. ciliates), Zooplanktons (e.g. Rotifers and copepods) and nematodes, heterotrophic bacteria and fungi. It was noted that the bacteria were all heterotrophic bacteria, which confirmed their utilisation of organic carbon in the BFT system to produce microbial protein. The biochemical composition of biofloc showed that the nutritional quality of biofloc was appropriate for tilapia with the exception of lipid content, which was found to be (3.25%). This value is considered low for aquaculture feed as a range of 5- 10% lipid content in feed is recommended. BFT is a promising field which will enable aquaculture to grow towards an environmentally friendly approach because of the ability of microorganisms to recycle nutrients in the system.

Valorisation of aquaculture sludge into microbial protein using bioreactor with an optimised nutrients

The present study was conducted to optimise the nutrients used for producing high nutritional biofloc in bioreactor utilising aquaculture waste. Full Factorial design (23) of independent variables such as sludge quantity (20 and 30 gL−1), carbon nitrogen ratio (15:1 and 20:1) and bioflocculant (cationic starch) doses (30 and 60 ppm) were used for optimisation. The percentage of crude protein and crude lipid in biofloc was shown to be significantly influenced by the interaction between carbon nitrogen ratio and bioflocculant dose (BC) as well as the interaction between sludge quantity, carbon nitrogen ratio, and bioflocculant dose (ABC) (p < 0.05). The floc volume of biofloc was shown to be significantly influenced by the interaction between carbon nitrogen ratio and bioflocculant dose (BC) (p < 0.05). The optimised parameters were 30 gL−1 of sludge, a carbon nitrogen ratio of 20:1, and 30 ppm of cationic starch, which resulted in a maximum CP of 27.09%, a maximum CL of 4.36%, and a maximum floc volume of 132 mL L−1. Principal component analysis (PCA) resulted in a 2 principal components (PC 1, nutritional factors which decides the nutritional composition of biofloc and PC 2, nitrification factors which are needed for biofloc formation) that explained 85% of total data variation. This study found the production of nutritive biofloc in a bioreactor using aquaculture waste with optimised nutrients.

Effect of C/N Ratio Levels and Stocking Density of Catla Spawn (Gibelion catla) on Water Quality, Growth Performance, and Biofloc Nutritional Composition in an Indoor Biofloc System

A 20-day 3 ∗ 3 factorial experiment was conducted in 100 L HDPE experimental tanks to investigate the effect of the C/N ratio (10, 15, and 20) and stocking density (3, 4, and 5 spawn L−1) on Gibelion catla spawn nursery rearing in the indoor biofloc system. Rice bran was used as the carbon source for manipulating C/N ratios. Each treatment was stocked with catla spawn of average length (6.7 ± 0.4 mm) and average weight (1.6 ± 0.2 mg). Water parameters showed that increasing the C/N ratio from 10 to 20 significantly ( p &lt; 0.05 ) reduced total ammonia nitrogen (TAN) and nitrite nitrogen (NO2-N) and increased nitrate nitrogen (NO3-N) in the water. The insignificant difference ( p &gt; 0.05 ) and lowest final average length, average length gain, average weight gain, and specific growth rate (SGR) were recorded in C/N ratios of 10 and 15 compared to a C/N ratio of 20. A significant difference ( p &lt; 0.05 ) in survival was observed with the increasing C/N ratio. Increasing the fish stocking density resulted in higher mortality. However, a higher amount of fry produced was observed in the treatments with 3 and 4 spawn L−1. Crude protein content increased significantly ( p &lt; 0.05 ) with the increasing C/N ratio with higher content in C/N 20. No significant difference ( p &gt; 0.05 ) in proximate composition of biofloc was observed in different stocking density groups. In conclusion, the application of the biofloc technology with a C/N ratio of 20 at a stocking density of 4 spawn L−1 could be recommended to increase the production of catla fry in the indoor biofloc system.

Dietary supplementation with soybean oil has not favored the tilapia growth in BFT tanks submitted to feeding restriction

The present work aimed at assessing the possibility of compensating the notorious deficiencies of bioflocs in lipids by supplementing the tilapia commercial diet with soybean oil. In the positive control, there was no feeding restriction nor dietary supplementation with soybean oil. In the experimental treatments, the commercial diet was restricted by 25% over the positive control level. In the negative control tanks, there was feeding restriction and the artificial diet had no oil supplementation. In the experimental tanks, soybean oil was mixed daily with the commercial diet at the levels of 0.6%, 1.2 and 2.4%. Additionally, there were fed-restricted tanks that received a daily supplementation of 1.2% soybean oil mixed with dry molasses, and not with the commercial diet. In general, only the restriction of the commercial diet affected the water quality. The supplementation of the artificial diet with soybean oil up to 2.4% has not improved the proximate composition of bioflocs, nor the fish growth performance. It was concluded that the strategy of supplementing the Nile tilapia juveniles’ commercial diet with increasing levels of soybean meal, in BFT tanks submitted to 25%-feeding restriction, was not capable of avoiding the fish growth performance deterioration.

Supplementation of the commercial diet of Nile tilapia (Oreochromis niloticus) with DL-methionine and soybean oil under feed restriction

This study aimed to assess the strategy of supplementing the commercial diet of Nile tilapia juveniles with DL-methionine and soybean oil, in BFT culture tanks, by monitoring the water quality, bioflocs composition, and growth performance. The commercial diet daily allowances were restricted by 25% and different levels of DL-methionine (0 and 1) and soybean oil (0, 0.6, and 1.2%) supplementation were carried out, having the delivery of artificial diet as reference. The tanks submitted to feeding restriction exhibited lower concentrations of organic matter, settleable solids and total suspended solid in water. The supplementation of the commercial diet with DL-methionine and soybean oil did not affect the centesimal composition of bioflocs. The combined use of DL-methionine and soybean oil improved the tilapia juveniles’ survival submitted to artificial diet restriction. It was concluded that the supplementation of the Nile tilapia’s commercial diet with 1.0% DL-methionine and 0.6% soybean oil may prevent the reduction of fish growth performance when the artificial diet is allowed restrictively.

Carbohydrate Supplement Impact on Growth Performance, Bacterial Community, and Bacterial Food Quality of Whiteleg Shrimp (Litopenaeus vannamei) under Biofloc System

Biofloc technology has a high impact on enhancing shrimp production. Suitable supplemented carbohydrates (CHO) could affect the type of microorganisms developed in the system, which reflects on shrimp production, food safety, and public health. Here, we aimed to compare the effects of sugarcane molasses and wheat flour as carbohydrate sources on biofloc technology. That was achieved through measuring the following parameters: water quality, growth performance, feed utilization, floc composition, shrimp whole body composition, microbial community, and biofloc shrimp food bacterial quality. Postlarvae of whiteleg shrimp (Litopenaeus vannamei) with a mean weight ( 38.47 ± 5.8 mg ) were stocked at a density of 200 individuals/m2 and cultured under a biofloc system for 128 days in six tanks with a total water volume of 30 m2 each. Water quality analysis revealed a better-dissolved oxygen concentration (5.59 mg/L) in the wheat flour treatment, whereas no significant differences were found between the two treatments in ammonia, nitrite, and pH levels. Increased turbidity (64.27 NTU) and floc volume (18.40 mL/L) were recorded with molasses treatment. Growth performance including final weight, weight gain, average daily gain, weight gain per week, and specific growth rate (12.37 g, 12.34 g, 0.096 g/d, 0.68, and 4.70%, respectively) were all significantly higher in the molasses treatment. Wheat flour treatment was associated with a higher survival rate (99%), biomass (71.16 Kg), and biomass increase percentage (395.337) in shrimps. It also improved feed utilization in terms of a lower feed conversion ratio (1.37) and higher protein efficiency ratio (1.92). The chemical composition of biofloc and shrimp whole body were both nutritious higher in wheat flour treatment. In water, total heterotrophic bacterial counts with sugarcane molasses treatment and wheat flour were estimated as 3.4 × 10 5 CFU / mL and 1.2 × 10 5 CFU / mL , respectively, with no significant difference. In both treatments, beneficial bacteria such as lactic acid bacteria and Enterobacter cloacae were identified in water with the absence of pathogenic Vibrio spp. Wheat flour had a significantly lower total Vibrio-like count (TVC). Shrimps had lower TVC ( 1.9 × 10 4 CFU / g ) with flour than with molasses ( 1.32 × 10 5 CFU / g ). Cronobacter spp. were associated with shrimps in BFT supplemented with molasses, which might pose a potential risk to food safety. In conclusion, the use of wheat flour was the best for shrimp production and shrimp food bacterial quality.

The Optimization of Dietary Protein Level and Carbon Sources on Biofloc Nutritive Values, Bacterial Abundance, and Growth Performances of Whiteleg Shrimp (Litopenaeusvannamei) Juveniles.

A biofloc technology-based 75-day indoor growth trial in an 80 L glass aquaria was conducted to evaluate the effects of two different carbon sources (sugarcane bagasse, SB, and wheat flour, WF) on the biofloc composition, bacterial abundance, and growth of whiteleg shrimp (Litopenaeus vannamei) juveniles (0.23 ± 0.04 g). Three different levels of dietary protein content (250, 300, and 350 g protein kg−1 diet) and two carbon sources (SB and WF) were applied (SB250, WF250, SB300, WF300, SB350, and WF350, respectively), comparing to a controlled diet without biofloc and fed on a 450 g protein kg−1 diet (C450). With the addition of SB and WF, water quality was in the ideal recommended ranges for L. vannamei culture. At the end of the experiment, the biofloc volume increased with increasing dietary protein levels. The nutritional value of biofloc in different treatments was influenced by dietary protein and added SB and WF. Increasing dietary protein significantly increased the protein and lipid contents of the produced biofloc. The use of WF as a carbon source significantly increased lipids and nitrogen-free extract in the biofloc. The total heterotrophic bacterial (THB) count was significantly higher (p < 0.05) in WF300 and WF350 than in the other treatments. The mean effect of the protein levels and carbon source was significantly reported, whereas the highest significant THB count was recorded with 300 dietary protein and using WF as a carbon source. The growth performances of L. vannamei fed with biofloc treatments were significantly (p < 0.05) higher than the C450 group. The highest final weight and weight gain were recorded in SB350 treatment. The feed conversion ratio was not affected by reducing dietary protein levels; meanwhile, the protein efficiency ratio increased significantly in biofloc treatments than in the control. Overall, the results demonstrate that, compared to the control treatment of 450 dietary protein, the biofloc treatments using WF as a carbon source could compensate for the reduction in the dietary protein levels in the diet of L. vannamei and maintain higher zootechnical performance.

​Effect of Distillery Spent Wash as Carbon Source in Biofloc System on Nutrient Profile of GIFT Tilapia

Background: Biofloc technology (BFT) is an ecofriendly aquaculture production system. In this, various carbon sources being used for floc production. However, the cheapest carbon source would make it economically feasible. In this context, the present study used purified distillery spent wash (DSW) as a carbon source to evaluate its viability on biofloc composition and carcass quality of GIFT strain. Methods: Nursery trial was conducted in high density poly ethylene (HDPE) outdoor lined pond (0.01 ha) for period of 30 days (8th January to 7th February 2018). In both BFT and control system, proximate composition and fatty acid profile of GIFT tilapia were analyzed at the end of the trial by following the standard method. Result: Dried microbial floc encompassed 16.61 ± 1.2% of crude protein and 15.3 ± 0.01% of linoleic acid. The Whole-body composition of GIFT was not significantly (P greater than 0.05) varied in between biofloc and control. Significantly (P less than 0.05) rich fatty acids found in biofloc fed GIFT whole body except stearic acid, behenic acid and docosahexaenoic acid. In the present study, DSW did not show much effect on carcass quality but showed better growth performance of GIFT strain in the BFT system.

Vegetable choline in feed for Nile tilapia (Oreochromis niloticus) raised in a biofloc technology system (BFT): Biofloc composition, chemical composition, and fatty acid profiles in meat

The objective of this study was to determine whether supplementation with vegetable choline (VC: 0, 400, 800, and 1200 mg kg−1 of feed) in feed for Nile tilapia (Oreochromis niloticus) raised in a biofloc system would promote changes in fatty acid (FA) profiles in the meat. We characterized the composition of the biofloc; that is, we evaluated the meat's chemical composition and FA profiles. Concerning proximate meat composition, moisture was significantly lower in the group fed 1200 mg kg−1 of VC when compared to those of other treatments. Lipid levels were significantly higher in treatments with 800 and 1200 mg kg−1 than in the control (0 mg kg−1). The total saturated fatty acids (SFA) in meat were significantly lower in the 400 mg kg−1 treatment than in the control treatment, while they were significantly higher in the 1200 mg kg−1 treatment when compared to the control treatment. Total monounsaturated fatty acids (MUFA) in meat were significantly lower in the 1200 mg kg−1 treatment than in the control treatment. Finally, total polyunsaturated fatty acids (PUFA) in meat were significantly higher in treatments with 800 and 1200 mg kg−1 than in the control treatment. Taken together, the data suggest that supplementation of VC in diets for Nile tilapia in biofloc treatment improved FA profiles of the meat. Levels of 400 and 800 mg kg−1 of diet led a decreased SFAs and increased PUFAs (mainly DHA) and MUFAs in the meat of tilapia, all of which desirable effects from the standpoint of the consumer.

Water quality and productive response of Litopenaeus vannamei reared in biofloc with addition of commercial strains of nitrifying bacteria and Lactobacillus rhamnosus

Different strategies have been adopted aiming to improve either performance, water quality and health on intensive shrimp farming, including the manipulation of the bacterial community in biofloc technology (BFT) systems. The experimental design was completely randomized, with three treatments in triplicate developed in BFT without water exchange; CONT (control, only BFT without external addition of bacteria); NIT (addition of nitrifying bacteria in BFT water); LACT (BFT with addition of Lactobacillus rahamnosus in the pelletized feed). The experiment was carried out under controlled conditions, with juveniles of white shrimp Litopenaeus vannamei (0.56 g / ind as initial weight). During the bioassay (35 days), the basic variables of water and nitrogenous compounds (TAN, NO2-N and NO3-N) were monitored. At the end of the experiment, the abundance of ammonium oxidizing bacteria AOB), heterotrophic bacteria and Vibrio-like bacteria, the proximal composition of the biofloc and the shrimp tissue were analyzed. There were significant differences in the levels of DO, pH, TSS and alkalinity. In the NIT treatment, the minimum amount of TAN and NO2-N was recorded, and the nitrification curves occurred in less time. In terms of bacteria profile, the highest abundance of heterotrophic bacteria in water was recorded in the LACT treatment (36.8 × 106 CFU / mL) and the highest amount of OAB and Vibrio-like bacteria (yellow colonies) occurred in the NIT treatment (7.5 × 106 and 10.6 × 103 CFU / mL, respectively). The proximal composition of biofloc was different, the protein varied from 20.04 to 25.59%, the highest corresponded to CONT. Similarly, the proximal composition of shrimp was different, the protein varied from 69.61 to 71.42%, the maximum was recorded in LACT. The best productive parameters were registered in the LACT and NIT treatments, (specific growth 5.31, 5.18% / day; survival 99.6, 99.0% and FCR: 0.94, 1.00, respectively). In our experimental conditions, the addition of external bacteria (nitrifying and Lactobacillus rhamnosus) had a significant positive impact on the quality of the water, proximal composition and productive parameters of the shrimp, as well as on the abundance of bacteria.

Microalgae and probiotic bacteria as biofloc inducers in a hyper-intensive Pacific white shrimp (Penaeus vannamei) culture

Biofloc systems in Pacific white shrimp (Penaeus vannamei) culture generate floccules that remove wastes, and hence, biofloc formation is promoted for shrimp production. This study evaluated the induction of biofloc formation using microalgae and probiotic bacteria in hyper-intensive Pacific white shrimp culture. The experiment was performed for six weeks in tanks (28,000 L each) stocked 350 ind m-3 and weight of 1400 ± 30 mg. Three treatments were assessed: 1) with two diatoms: Grammatophora sp. and Navicula sp., 2) with Navicula sp., and 3) without diatoms. All treatments were added with Schizochytrium sp. and Lactobacillus fermentum TD19. The following parameters were monitored during culture: ammonium, nitrites, nitrates, environmental variables, floccules volume, microorganism presence, the bromatological composition of biofloc, and growth performance parameters of P. vannamei. Our results indicated that the three induced biofloc presented a similar volume (8.34 ± 4.8 mL L-1) and ammonium concentration (&lt;1.0 mg L-1). Treatment 1 generated floccules with the highest concentration of ciliates, rotifers, nematodes, lactic acid bacteria, and the lowest concentration of Vibrio spp. (1.2×103 UFC mL-1), evidencing a significant difference in bromatological composition, with the highest protein and lipid values (28.12 ± 0.50 and 22.44 ± 0.80% biofloc dry weight, respectively) and the best feed conversion ratio (0.89). Based on these results, we suggest that Schizochytrium sp., L. fermentum, and two diatoms should be used to induce biofloc in a hyper-intensive culture of P. vannmaei in order to provide a supplementary nutritional intake, which can constitute an advantage to reduce commercial feed rations.

Proximate Chemical Composition of Dried Shrimp and Tilapia Waste Bioflocs Produced by Two Drying Methods

The effects of two waste sources, red hybrid tilapia (Oreochromis sp.) and whiteleg shrimp (Litopenaeus vannamei), and two drying methods (freeze-drying and oven-drying) on the proximate chemical composition of bioflocs were investigated. In total, four kinds of experimentally treated bioflocs were compared to identify the best waste source and drying method to produce biofloc of an acceptable nutrient value: freeze-dried shrimp biofloc (FDSBF), oven-dried shrimp biofloc (ODSBF), freeze-dried tilapia biofloc (FDTBF), and oven-dried tilapia biofloc (ODTBF). The protein, lipid, ash, fiber, total nitrogen free extract (NFE), and energy contents of the dried bioflocs ranged from 12.12 to 24.09 g/100 g, 0.35 to 0.92 g/100 g, 42.45 to 61.01 g/100 g, 7.43 to 17.11 g/100 g, 16.45 to 18.59 g/100 g, and 0.99 to 1.94 Kcal g−1, respectively. Statistically, there were significant differences within the means of the two biofloc sources in terms of their proximate compositions (p &lt; 0.05). The average values between the drying methods for protein, lipid, total NFE, and energy were also significantly different, while no significant differences (p &gt; 0.05) were recorded for ash and fiber. Amino acids (AAs) were higher in FDTBF, followed by ODTBF. The mineral profiles showed that phosphorous, potassium, manganese, selenium, and copper were higher in the tilapia waste bioflocs, while calcium, zinc, iron, copper, chromium, and cobalt were higher in the shrimp waste bioflocs. Although the statistical analysis showed that the shrimp waste bioflocs had higher levels of lipid, fiber, total NFE, and minerals, the tilapia waste bioflocs contained higher levels of potential AAs, energy, and protein, which are regarded as expensive ingredients in aquaculture feeding. This study indicates that biofloc derived from tilapia waste can be regarded as a more suitable source of biofloc meal (in terms of protein, ash, energy, and AAs) than biofloc derived from shrimp waste. Our findings also suggest that freeze-drying is a more effective drying method for drying biofloc, as it efficiently maintains nutritional quality.

Effects of different carbon sources on water quality, biofloc quality, and growth performance of Nile tilapia (Oreochromis niloticus) fingerlings in a heterotrophic culture system

The biofloc system is one of the novel sustainable aquaculture systems, and adding carbonaceous organic matter is the basis of the system. This study aimed to evaluate the effects of different carbon sources on water quality, biofloc composition, and growth performance of Nile tilapia (Oreochromis niloticus). In this study, one control group (no carbon source addition) and four biofloc treatments with molasses (TM), starch (TS), barley flour (TB), and corn (TC) addition with three replications were considered. Altogether, 160 Nile tilapia with an average weight of 1.7 g were stocked in each of the 300-l tanks (160 l of water volume). The results of water quality indicated that the lowest levels of dissolved oxygen (5.43 mg/l) and pH (7.28) were observed in the TS treatment, which showed a significant difference (P < 0.05) compared to other treatments. There was a significant difference among various treatments in nitrogen compounds and the total density of heterotrophic bacteria. Biochemical quality of biofloc was affected by various carbon sources. The highest levels of protein (31.09%), lipid (3.89%), and ash (32.79%) were observed in TB, TC, and TM treatments, respectively. The largest biofloc size was obtained in TS treatment. The lowest survival rate and the highest level of weight gain of Nile tilapia were observed in control group. In conclusion, the present study showed that different sources of carbon in the biofloc system have different effects on water quality, biochemical composition, and biofloc size produced in cultivation tanks.

Heterotrophic, chemoautotrophic and mature approaches in biofloc system for Pacific white shrimp

This work aimed to evaluate three different strategies for rearing L. vannamei in a biofloc system: heterotrophic, chemoautotrophic and a mature biofloc system relative to the effects of water quality, water bacterial community, biofloc composition and yield. To accomplish this, a study lasting 35 days was conducted with juvenile (3.46 g) shrimps stocked in twelve 300 L tanks at a stocking density of 350 shrimp m3. For heterotrophic treatment, water received molasses as a carbon source. For chemoautotrophic treatment, ammonium and nitrite salts were added to the water. The mature treatment was created by adding a significant amount of water containing mature biofloc from another established biofloc technology (BFT) system. In both mature and chemoautotrophic treatments, the nitrification process could maintain toxic nitrogen compounds (ammonia and nitrite) at low levels without the addition of carbohydrates. In contrast, the heterotrophic system had peaks of ammonia and nitrite during the rearing cycle. The heterotrophic system also had a significantly higher value of volatile solids and total suspended solids compared to the other treatments. Analysis of the biofloc system revealed a relatively high proportion of protein, but the proportion of protein in the heterotrophic system was higher. Chemoautotrophic and mature treatments maintained the water quality at a constant level, especially nitrogen removal. Metagenomic analysis showed the microbial community associated with the biofloc system to be represented by 10 phyla. In all treatments, the five most abundant phyla were the following: Proteobacteria, Bacteroidetes, Chloroflexi, Actinobacteria, and Gemmatimonadetes. Shrimp performance demonstrated that heterotrophic, mature and chemoautotrophic systems are suitable approaches for shrimp rearing in BFT.