Nutritional applications of species of Spirulina and Chlorella in farmed fish: A review

Green microbes: Potential solutions for key sustainable development goals

The latest assessment of progress towards the Sustainable Development Goals (SDGs) has identified major obstacles, such as climate change, global instability and pandemics, which threaten efforts to achieve the SDGs even by 2050. Urgent action is needed, particularly to reduce poverty, hunger and climate change. In this context, microalgae are emerging as a promising solution, particularly in the context of food security and environmental sustainability. As versatile organisms, microalgae offer nutritional benefits such as high-quality proteins and essential fatty acids, and can be cultivated in non-arable areas, reducing competition for resources and improving the sustainability of food systems. The role of microalgae also includes other applications in aquaculture, where they serve as sustainable alternatives to animal feed, and in agriculture, where they act as biofertilizers and biostimulants. These microorganisms also play a key role in interventions on degraded land, stabilizing soils, improving hydrological function and increasing nutrient and carbon availability. Microalgae therefore support several SDGs by promoting sustainable agricultural practices and contributing to land restoration and carbon sequestration efforts. The integration of microalgae in these areas is essential to mitigate environmental impacts and improve global food security, highlighting the need for increased research and development, as well as public and political support, to exploit their full potential to advance the SDGs.

Hematological and anthelminthic responses of tambaqui (Colossoma macropomum) supplemented with Artrhospira platensis and Chlorella vulgaris

The present study evaluated the hematological, antiparasitic and growth responses in tambaqui (Colossoma macropomum) fed with diets supplemented with the microalgae Arthrospira platensis and Chlorella vulgaris (0%; 10% A. platensis; 10% C. vulgaris; and 5% A. platensis+5% C. vulgaris). Tambaqui (n=60, 62.57 ± 8.76 g) were fed for 20 days with experimental diets. Blood samples collection was done to determine hematological parameters, and gills were removed to identify and count monogenetic parasites. Supplementation with A. platensis 10% reduced red blood cells count, in consequence mean corpuscular volume and mean hemoglobin concentration increased. Total leukocyte, monocyte, eosinophil, and basophil counts reduced with the use of A. platensis. Higher monocytes, eosinophil, and basophil numbers in tambaqui fed with diet supplemented with 10% C. vulgaris were observed and may have been due to the presence of immunostimulants in this microalga composition. Reduction on total cholesterol in tambaqui that received both microalgae (A. platensis 5%+C. vulgaris 5%) may indicate that combined supplementation presented greater benefits to the health for C. macropomum than separately. Both microalgae were efficient against monogenetic parasites of tambaqui. Thus, the dietary use of the microalgae A. platensis and C. vulgaris provided immunostimulant and antiparasitic efficacy in C. macropomum.

Recovery of nutrients from fish sludge to enhance the growth of microalga Chlorella sorokiniana CMBB276

Intensive aquaculture production generates large amounts of sludge. This waste could be considered as a potential source of nutrients that can be recovered and utilized. Little attention has been paid to nutrient recovery from fish sludge. In this study, bioconversion of sludge was evaluated in lab scale under anaerobic (AN), facultative anaerobic (FA) and aerobic (AE) conditions. After 40 days of fermentation, AN recovered the highest values of dissolved total nitrogen (82.7 mg L-1), while AE showed the highest dissolved total phosphorus (11.8 mg L-1) and the highest reduction of total suspended solids (36.0 %). Microbial analysis showed that AN exhibited a distinct bacterial community than that of FA and AE. Furthermore, C. sorokiniana grown in AN effluents collected after 12 days of fermentation achieved the highest biomass production (1.96 g L-1). These results suggest that AN has the best potential to recover nutrients from sludge for production of C. sorokiniana.

A Pretty Kettle of Fish: A Review on the Current Challenges in Mediterranean Teleost Reproduction

The Mediterranean region is facing several environmental changes and pollution issues. Teleosts are particularly sensitive to these challenges due to their intricate reproductive biology and reliance on specific environmental cues for successful reproduction. Wild populations struggle with the triad of climate change, environmental contamination, and overfishing, which can deeply affect reproductive success and population dynamics. In farmed species, abiotic factors affecting reproduction are easier to control, whereas finding alternatives to conventional diets for farmed teleosts is crucial for enhancing broodstock health, reproductive success, and the sustainability of the aquaculture sector. Addressing these challenges involves ongoing research into formulating specialized diets, optimizing feeding strategies, and developing alternative and sustainable feed ingredients. To achieve a deeper comprehension of these challenges, studies employing model species have emerged as pivotal tools. These models offer advantages in understanding reproductive mechanisms due to their well-defined physiology, genetic tractability, and ease of manipulation. Yet, while providing invaluable insights, their applicability to diverse species remains constrained by inherent variations across taxa and oversimplification of complex environmental interactions, thus limiting the extrapolation of the scientific findings. Bridging these gaps necessitates multidisciplinary approaches, emphasizing conservation efforts for wild species and tailored nutritional strategies for aquaculture, thereby fostering sustainable teleost reproduction in the Mediterranean.

Effects of varying dietary microalgae levels on performance, egg quality, fertility, and blood biochemical parameters of laying Japanese quails (Coturnix coturnix Japonica)

This experiment was carried out to investigate the nutritional value of Spirulina and Dunaliella (SD) combination levels (0, 0.5, 1.0, 1.5, and 2.0 g/kg) that affected the laying Japanese quail's efficiency, egg quality, fertility, and blood biological indicators. A total of 150 adult Japanese quails, aged 8 wk, were divided into 5 treatments at random, each consisting of 30 quails. There were 5 duplicates for every treatment, with 2 male and 4 female quails in each. Comparing the addition of various concentrations of a mixture of SD to the control treatment, the results showed no substantial rise in egg production, egg weight, or egg mass. When compared to the control group, final body weight (FBW) was improved with SD supplementation. The quails in control consumed more feed intake (FI) (p < 0.05), and they were different from the groups who got SD therapy in that they had a regular feed conversion ratio (FCR). The percentages of hatchability and fertility increased when SD was added to quail meals at up to 1.00 g/kg. When compared to the control quail, the quail supplemented with SD levels showed a non-significant rise in albumin%, yolk%, Haugh unit, and unit surface shell weight (USSW), as well as an increase in eggshell percentage and a drop in egg shape index (p < 0.05). Renal and hepatic enzyme functioning improved when SD was added to the diets. Additionally, lipid profile indicators were reduced by SD supplementation (except low-density lipoprotein-LDL). Moreover, compared to the control, incorporating SD led to a nonsignificant rise in immunoglobulin concentrations (IgG and IgM). In conclusion, adding SD to the diet can improve body weight, lipid profile, immunological response, and liver and kidney functions in Japanese quail.

Nanosynthesis, phycochemical constituents, and pharmacological properties of cyanobacterium Oscillatoria sp

The Oscillatoria sp., a blue-green alga or cyanobacterium, consists of about 305 species distributed globally. Cyanobacteria are prokaryotes possessing several secondary metabolites that have industrial and biomedical applications. Particularly, the published reviews on Oscillatoria sp. have not recorded any pharmacology, or possible details, while the detailed chemical structures of the alga are reported in the literature. Hence, this study considers pertinent pharmacological activities of the plethora of bioactive components of Oscillatoria sp. Furthermore, the metallic nanoparticles produced with Oscillatoria sp. were documented for plausible antibacterial, antifungal, antioxidant, anticancer, and cytotoxic effects against several cultured human cell lines. The antimicrobial activities of solvent extracts of Oscillatoria sp. and the biotic activities of its derivatives, pyridine, acridine, fatty acids, and triazine were structurally described in detail. To understand the connotations with research gaps and provide some pertinent prospective suggestions for further research on cyanobacteria as potent sources of pharmaceutical utilities, attempts were documented. The compounds of Oscillatoria sp. are a potent source of secondary metabolites that inhibit the cancer cell lines, in vitro. It could be expected that by holistic exploitation, the natural Oscillatoria products, as the source of chemical varieties and comparatively more potent inhibitors, would be explored against pharmacological activities with the integument of SARs.

Acrylamide exposure induces growth retardation, neurotoxicity, stress, and immune/antioxidant disruption in Nile tilapia (Oreochromis niloticus): The alleviative effects of Chlorella vulgaris diets

This study looked at the toxic impacts of water-born acrylamide (ACR) on Nile tilapia (Oreochromis niloticus) in terms of behaviors, growth, immune/antioxidant parameters and their regulating genes, biochemical indices, tissue architecture, and resistance to Aeromonas hydrophila. As well as the probable ameliorative effect of Chlorella vulgaris (CV) microalgae as a feed additive against ACR exposure was studied. The 96-h lethal concentration 50 of ACR was investigated and found to be 34.67 mg/L for O. niloticus. For the chronic exposure study, a total of 180 healthy O. niloticus (24.33 ± 0.03 g) were allocated into four groups in tri-replicates (15 fish/replicate), C (control) and ACR groups were fed a basal diet and exposed to 0 and 1/10 of 96-h LC50 of ACR (3.46 mg/L), respectively. ACR+ CV5 and ACR+ CV10 groups were fed basal diets with 5 % and 10 % CV supplements, respectively and exposed to 1/10 of 96-h LC50 of ACR for 60 days. After the exposure trial (60 days) the experimental groups were challenged with A. hydrophila. The findings demonstrated that ACR exposure induced growth retardation (P˂0.01) (lower final body weight, body weight gain, specific growth rate, feed intake, protein efficiency ratio, final body length, and condition factor as well as higher feed conversion ratio). A substantial decrease in the immune/antioxidant parameters (P˂0.05) (lysozyme, serum bactericidal activity %, superoxide dismutase, and reduced glutathione) and neurotransmitter (acetylcholine esterase) (P˂0.01) was noticed with ACR exposure. A substantial increase (P˂0.01) in the serum levels of hepato-renal indicators, lipid peroxidation biomarker, and cortisol was noticed as a result of ACR exposure. ACR exposure resulted in up-regulation (P˂0.05) of the pro-inflammatory cytokines and down-regulation (P˂0.05) of the antioxidant-related gene expression. Furthermore, the hepatic, renal, brain, and splenic tissues were badly affected by ACR exposure. ACR-exposed fish were more sensitive to A. hydrophila infection and recorded the lowest survival rate (P˂0.01). Feeding the ACR-exposed fish with CV diets significantly improved the growth and immune/antioxidant status, as well as modulating the hepatorenal functions, stress, and neurotransmitter level compared to the exposed-non fed fish. In addition, modulation of the pro-inflammatory and antioxidant-related gene expression was noticed by CV supplementation. Dietary CV improved the tissue architecture and increased the resistance to A. hydrophila challenge in the ACR-exposed fish. Noteworthy, the inclusion of 10 % CV produced better results than 5 %. Overall, CV diets could be added as a feed supplement in the O. niloticus diet to boost the fish's health, productivity, and resistance to A. hydrophila challenge during ACR exposure.

Microalgae as fishmeal alternatives in aquaculture: current status, existing problems, and possible solutions

Fishmeal is an indispensable ingredient for most aquatic animals. However, the finite supply and escalating price of fishmeal seriously limit its use in aquaculture. Thus the development of new, sustainable protein ingredients has been a research focus. Microalgae are potential fishmeal alternatives owing to their high protein content and balanced amino acid profile. Studies suggest that suitable replacement of fishmeal with microalgae is beneficial for fish growth performance, but excessive replacement would induce poor growth and feed utilization. Therefore, this paper aims to review research on the maximum substitutional level of fishmeal by microalgae and propose the main issues and possible solutions for fishmeal replacement by microalgae. The maximum replacement level is affected by microalgal species, fish feeding habits, quality of fishmeal and microalgal meals, and supplemental levels of fishmeal in the control group. Microalgae could generally replace 100%, 95%, 95%, 64.1%, 25.6%, and 18.6% fishmeal protein in diets of carp, shrimp, catfish, tilapia, marine fish, and salmon and trout, respectively. The main issues with fishmeal replacement using microalgae include low production and high production cost, poor digestibility, and anti-nutritional factors. Possible solutions to these problems are recommended in this paper. Overall, microalgae are promising fishmeal alternatives in aquaculture.

Growth, carcass criteria, and blood biochemical parameters of growing quails fed Arthrospira platensis as a feed additive

This study investigated the impact of Arthrospira platensis (A. platensis) as a dietary supplement on growth, carcass criteria, liver and kidney function, lipid profile, and immunity of growing Japanese quails. In a 28-day experiment, 240 unsexed 7-day-old quail chicks were used. The quail chicks were divided into 4 treatment sets, each comprising 6 replicates and 10 quail chicks. Group (1) fed the basal diet with no supplements, group (2) fed the basal diet supplemented with 0.25 g A. platensis/kg diet, group (3) fed the basal diet supplemented with 0.50 g A. platensis/kg diet, and group (4) fed the basal diet supplemented with 1.00 g A. platensis/kg diet. The results of this study revealed that the birds that were fed 0.50 g. or 1.00 g A. platensis/kg diet had superior final body weights, body weight gains, feed conversion ratios, and carcass criteria compared to control, furthermore, had significant (P < 0.05) lower levels of liver enzymes and kidney function markers compared to control. Furthermore, birds fed 0.50 g or 1.00 g A. platensis/kg diet had significantly (P < 0.05) reduced cholesterol, triglycerides, and LDL cholesterol levels compared to control. Dietary supplementation of A. platensis at 0.50 and 1.00 g/kg diet significantly (P < 0.05) increased total antioxidant capacity, total immunoglobulin, and lysozyme activity levels. Using A. platensis at 0.5 or 1 g/kg diet levels during the Japanese quails' growth period can improve growth, carcass criteria, liver and kidney function, lipid profile, and immunity.

Enhanced Photosynthetic Pigment Production Using a Scaled-Up Continuously Circulated Bioreactor

Microalgae have gained attention as a promising source of chlorophylls and carotenoids in various industries. However, scaling up of conventional bubble columns presents challenges related to cell sedimentation and the presence of non-photosynthetic cells due to non-circulating zones and decreased light accessibility, respectively. Therefore, this study aimed to evaluate the newly developed continuously circulated bioreactor ROSEMAX at both laboratory and pilot scales, compared to a conventional bubble column. There was no significant difference in the biomass production and photosynthetic pigment content of Tetraselmis sp. cultivated at the laboratory scale (p > 0.05). However, at the pilot scale, the biomass cultured in ROSEMAX showed significantly high biomass (1.69 ± 0.11 g/L, dry weight, DW), chlorophyll-a (14.60 ± 0.76 mg/g, DW), and total carotene (5.64 ± 0.81 mg/g, DW) concentrations compared to the conventional bubble column (1.17 ± 0.11 g/L, DW, 10.67 ± 0.72 mg/g, DW, 3.21 ± 0.56 mg/g, DW, respectively) (p ≤ 0.05). Flow cytometric analyses confirmed that the proportion of Tetraselmis sp. live cells in the culture medium of ROSEMAX was 32.90% higher than that in the conventional bubble column, with a photosynthetic efficiency 1.14 times higher. These results support suggestions to use ROSEMAX as a bioreactor for industrial-scale applications.

Emerging Applications of Chlorella sp. and Spirulina (Arthrospira) sp

Chlorella sp. and Spirulina (Arthrospira) sp. account for over 90% of the global microalgal biomass production and represent one of the most promising aquiculture bioeconomy systems. These microorganisms have been widely recognized for their nutritional and therapeutic properties; therefore, a significant growth of their market is expected, especially in the nutraceutical, food, and beverage segments. However, recent advancements in biotechnology and environmental science have led to the emergence of new applications for these microorganisms. This paper aims to explore these innovative applications, while shedding light on their roles in sustainable development, health, and industry. From this state-of-the art review, it was possible to give an in-depth outlook on the environmental sustainability of Chlorella sp. and Spirulina (Arthrospira) sp. For instance, there have been a variety of studies reported on the use of these two microorganisms for wastewater treatment and biofuel production, contributing to climate change mitigation efforts. Moreover, in the health sector, the richness of these microalgae in photosynthetic pigments and bioactive compounds, along with their oxygen-releasing capacity, are being harnessed in the development of new drugs, wound-healing dressings, photosensitizers for photodynamic therapy, tissue engineering, and anticancer treatments. Furthermore, in the industrial sector, Chlorella sp. and Spirulina (Arthrospira) sp. are being used in the production of biopolymers, fuel cells, and photovoltaic technologies. These innovative applications might bring different outlets for microalgae valorization, enhancing their potential, since the microalgae sector presents issues such as the high production costs. Thus, further research is highly needed to fully explore their benefits and potential applications in various sectors.

Enhancing Rearing of European Seabass (Dicentrarchus labrax) in Aquaponic Systems: Investigating the Effects of Enriched Black Soldier Fly (Hermetia illucens) Prepupae Meal on Fish Welfare and Quality Traits

Within the modern aquaculture goals, the present study aimed to couple sustainable aquafeed formulation and culturing systems. Two experimental diets characterized by 3 and 20% of fish meal replacement with full-fat spirulina-enriched black soldier fly (Hermetia illucens) prepupae meal (HPM3 and HPM20, respectively) were tested on European seabass (Dicentrarchus labrax) juveniles during a 90-day feeding trial performed in aquaponic systems. The experimental diets ensured 100% survival and proper zootechnical performance. No behavioral alterations were evidenced in fish. Histological and molecular analyses did not reveal structural alterations and signs of inflammation at the intestinal level, highlighting the beneficial role on gut health of bioactive molecules typical of HPM or derived from the enriching procedure of insects' growth substrate with spirulina. Considering the quality traits, the tested experimental diets did not negatively alter the fillet's fatty acid profile and did not compromise the fillet's physical features. In addition, the results highlighted a possible role of spirulina-enriched HPM in preserving the fillet from lipid oxidation. Taken together, these results corroborate the use of sustainable ingredients (spirulina-enriched HPM) in aquaponic systems for euryhaline fish rearing.

Combined effects of Spirulina platensis and Pediococcus acidilactici on the growth performance, digestive enzyme activity, antioxidative status, and immune genes in zebrafish

The combined effects of Spirulina platensis (SP) and Pediococcus acidilactici (PA) on growth performance, digestive enzyme activity, antioxidative status, and immune genes in zebrafish were investigated in the present study. Four experimental diets were designed: control and three test diets mixed with SP at 2.5%, PA at 107 CFU/g, or a combination of 2.5% SP and 107 CFU/g PA. After 56 days, fish treated with PA and SP mixture had higher final weight, weight gain, SGR, and lower FCR than fish fed the control and SP diets (P<0.05). The results also illustrated that fish fed PA, SP, and their mixture had higher (P<0.05) protease and amylase activities than the control. The lipase activity was significantly higher in fish treated with PA or the mixture of PA and SP than in the control (P<0.05). The alternative complement pathway (ACH50) and lysozyme activity in the mucus samples of fish treated with PA or both PA and SP were significantly higher (P<0.05) than in fish treated with the control and SP diets. The total immunoglobulin level in the skin mucus was significantly higher (P<0.05) in fish fed PA than in control. In the body homogenates samples, the lysozyme activity and immunoglobulin levels were markedly higher (P<0.05) in fish treated with the mixture of PA and SP than in the control. The dietary PA and SP diet mixture improved the glutathione peroxidase, superoxide dismutase, and total antioxidative capacity. The expression of IL-1β and IL-8 genes in fish treated with PA or the mixture of PA and SP was significantly higher (P<0.05) than in fish treated with the control or SP diets. Fish treated with PA, SP, or both PA and SP had marked (P<0.05) upregulation of the lysozyme gene expression. In conclusion, the mixture of S. platensis and P. acidilactici is more effective than using each individually for improving the growth performance, digestive enzyme activity, and the immune and antioxidative capacity of zebrafish.

Benefits of the microalgae Spirulina and Schizochytrium in fish nutrition: a meta-analysis

Use of microalgae in fish nutrition can relieve pressure on wild fish stocks, but there is no systematic quantitative evaluation of microalgae benefits. We conducted a metanalysis on the nutritional benefits of Spirulina and Schizochytrium as replacements of fishmeal and fish or plant oil, respectively. We reviewed 50 peer-reviewed studies involving 26 finfish species and 144 control vs microalgae replacement comparisons. Inclusion of Spirulina in the fish diet significantly improved growth compared to controls (SMD = 1.21; 95% CI 0.71-1.70), while inclusion of Schizochytrium maintained the content of omega-3 PUFA of the fish fillet compared to fish fed on fish or plant oils (SMD = 0.62; 95% CI - 0.51-1.76). Benefits were apparent at replacement levels as low as 0.025% in the case of Spirulina and 10% in the case of Schizochytrium oil. Dose-dependent effects were found for Spirulina replacement on growth, but not for Schizochytrium on omega-3 fillet content. Subgroup analysis and meta-regression revealed that ~ 24-27% of variation in effect sizes can be accounted by variation between fish families, the rest likely reflecting variation in experimental conditions. Overall, the evidence indicates that Spirulina and Schizochytrium replacement in aquafeeds can be used to improve fish growth and maintain fillet quality, respectively, but considerable uncertainty exists on the predicted responses. To reduce uncertainty and facilitate the transition towards more sustainable aquafeeds, we recommend that feeding trials using microalgae are conducted under commercially relevant conditions and that greater care is taken to report full results to account for sources of heterogeneity.

Spirulina-enriched Substrate to Rear Black Soldier Fly (Hermetia illucens) Prepupae as Alternative Aquafeed Ingredient for Rainbow Trout (Oncorhynchus mykiss) Diets: Possible Effects on Zootechnical Performances, Gut and Liver Health Status, and Fillet Quality

In the present study, an organic substrate (coffee silverskin) enriched with spirulina (Arthrospira platensis; 15% w/w), as a source of lipids and bioactive molecules, was used to rear the black soldier fly (Hermetia illucens) prepupae. Three grossly isonitrogenous, isoproteic, isolipidic and isoenergetic experimental diets for rainbow trout (Oncorhynchus mykiss) juveniles were then produced: a control diet (HM0) mostly including fish meal and fish oil, and two other test diets named HM3 and HM20, in which 3 or 20% of the marine ingredients were substituted with full fat black soldier fly prepupae meal (HM), respectively. Experimental diets were provided for 6 weeks, and at the end of the trial the physiological responses and marketable traits of the fish were investigated using a multidisciplinary approach. Generally, all test diets were well accepted, and fish growth, gut and liver health status, and marketable characteristics were not impaired by the experimental diets. However, an increased immuno-related gene expression along with a slight reduction of fillet redness and yellowness was evident in fish from the HM20 group.

Effect of Spirulina Meal Supplementation on Growth Performance and Feed Utilization in Fish and Shrimp: A Meta-Analysis

The application potential of spirulina meal in aquaculture feeds has been well summarized in several descriptive reviews. Nevertheless, they converged on compiling results from all possible relevant studies. Little available quantitative analysis regarding the pertinent topics has been reported. This quantitative meta-analysis was performed to investigate the influences of dietary spirulina meal (SPM) addition on responsive variables in aquaculture animals, including final body weight (FBW), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), condition factor (CF), and hepatosomatic index (HSI). The pooled standardized mean difference (Hedges' g) and 95% confidence limit were computed to quantify the primary outcomes based on random-effects model. The sensitivity and subgroup analyses were carried out to evaluate the validity of the pooled effect size. The meta-regression analysis was conducted to investigate the optimal inclusion of SPM as a feed supplement and the upper threshold of SPM usage for substituting fishmeal in aquaculture animals. The results indicated that on the whole, dietary SPM addition significantly improved FBW, SGR, and PER; statistically decreased FCR of animals; had no significant influence on CF and HSI. The growth-enhancing effect of SPM inclusion in the form of feed additive was significant; however, the effect was indistinctive in the form of feedstuff. Furthermore, the meta-regression analysis displayed that the optimal levels of SPM as a feed supplement in fish and shrimp diets were 1.46%-2.26% and 1.67%, respectively. Additionally, up to 22.03%-24.53% and 14.95%-24.85% of SPM as fishmeal substitute did not have a negative effect on growth and feed utilization in fish and shrimp, respectively. Therefore, SPM is a promising fishmeal substitute and a growth-promoting feed additive for sustainable aquaculture of fish and shrimp.

Effect of environmental factors on growth performance of Nile tilapia (Oreochromis niloticus)

Aquaculture is the practice of developing aquatic animals and plants under artificial environmental conditions, either in a controlled or semi-controlled environment. Due to high animal protein demand, it is one of the world's growing food production industries. It plays a vital role in contributing to food security and lowering the unemployment rate of the world's growing population. This review article aims to scope sight on the environmental factors that affect the growth and economic production process of Nile tilapia. Many of these factors are listed and analyzed in this review, such as stocking densities; various feed frequencies and feeding rates; water quality; water temperature; dissolved oxygen concentration; water pH degree; ammonia (NH3), nitrite (NO2), and nitrate (NO3) concentration; feeding regimes; feed cost; and tank culturing system of Nile tilapia. These factors can significantly alter body weight, composition, survival, behavior, feed intake, feed conversion ratio, feeding efficiency, and the health and reproduction of Oreochromis niloticus. Furthermore, feeding, growth, disease risks, and survival rates are all affected by water quality parameters. In general, higher growth performance of O. niloticus in aquaculture can be obtained by keeping the optimum quantity of feed with proper feeding rate and frequency, maintaining a good proportion of stocking density, and regularly evaluating water quality. This review article highlights-in details-the impact of various environmental factors on growth performance criteria of Nile tilapia (Oreochromis niloticus).

High replacement of fishmeal by Chlorella meal affects intestinal microbiota and the potential metabolic function in largemouth bass (Micropterus salmoides)

Microalgae have beneficial effects on the performance of fish as additives and they are becoming a promising alternative to fishmeal as macronutrient ingredients. However, the impact on the fish intestinal microbiome and the function, caused by microalgae as protein sources in diets, remains unclear. This study aimed to determine the composition and potential function of the intestinal microbial community of largemouth bass (Micropterus salmoides) fed diets at five replacement levels (0, 25, 50, 75 and 100%) of fishmeal by Chlorella meal in a basal diet (400 g kg⁻¹) after 8 weeks. The results showed significant decreases in unique amplicon sequence variants in the intestine at the higher levels of fishmeal replacement. At 50% of fishmeal replacement, dietary inclusions of Chlorella meal had no impact on species richness and Shannon diversity and the community structure of the intestinal microbiota. However, high levels of fishmeal replacement (75 and 100%) significantly induced intestinal community disturbance and diversity loss in largemouth bass. Responding to the high fishmeal replacement level, the dominant genus Cetobacterium and Pleslomonas sharply increased and several taxa from Lactobacillus decreased significantly. Functional data predicted by PICRUSt revealed that nutrition-related metabolism was dominant in the intestinal microbiota of fish fed all the five diets, although some potential functions, particularly amino acid and lipid metabolisms, and energy metabolism, were upregulated firstly, and then downregulated in fish fed diets with the increase of dietary Chlorella meal. Meanwhile, certain pathways were not enriched in intestinal microbiome until up to 75% of fishmeal replacement, such as carbohydrate metabolism, and cofactors and vitamins metabolism. To conclude, this study reveals that fishmeal replacement (50%) by Chlorella meal at the level of 237 g kg⁻¹ in diets is feasible for largemouth bass without impairing the microbiome structure and the metabolism function, providing an alternative strategy for evaluating the possibility of fishmeal replacement by microalgae in aquafeeds.

Effects of fish meal replacement with Chlorella meal on growth performance, pigmentation, and liver health of largemouth bass (Micropterus salmoides)

Chlorella meal is a potential protein source for aquafeeds. However, the physiological response of carnivorous fish fed Chlorella meal remains elusive. This study evaluated the effects of replacing dietary fish meal with Chlorella meal on growth performance, pigmentation, and liver health in largemouth bass. Five diets were formulated to replace dietary fish meal of 0% (C0, control), 25% (C25), 50% (C50), 75% (C75), and 100% (C100) with Chlorella meal, respectively. Total 300 fish (17.6 ± 0.03 g) were randomly assigned to 15 tanks (3 tanks/group). Fish were fed the experimental diet twice daily for 8 weeks. The increased dietary Chlorella meal quadratically influenced the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), and feed intake (FI), which were significantly lower in the C100 group than in the other groups (P < 0.05). The feed conversion ratio (FCR) increased linearly or quadratically with dietary Chlorella meal. Dietary Chlorella meal linearly or quadratically increased the lutein content of plasma, liver, and dorsal muscle of largemouth bass (P < 0.05). Compared to the C0 group, all supplemented Chlorella meal groups significantly improved the yellowness (b∗) of the dorsal body (1.5 to 2.0 fold), abdominal body (1.5 to 1.8 fold), and dorsal muscle (3.8 to 5.4 fold) of largemouth bass (P < 0.05). In addition, compared to the C0 group, the liver vacuolation area of fish was significantly increased in the C75 and C100 groups (P < 0.05). Transcriptional levels of apoptosis-related genes of β-cell lymphoma-2 (bcl2), caspase-9-like (casp9), and caspase-3a (casp3) were markedly upregulated (0.9 to 1.6 fold) in the C100 group compared to the C0 group (P < 0.05). Based on the quadratic regression analysis between FBW, WGR, or SGR and dietary Chlorella meal level, largemouth bass had the best growth when replacing 31.7% to 32.6% of fish meal with 15.03% to 15.43% dietary Chlorella meal. The present results indicated that dietary supplementation with Chlorella meal (11.85% to 47.45%) significantly enhanced the pigmentation; however, total replacement of fish meal (40%) with Chlorella meal (47.45%) caused growth retardation, apoptosis, and liver damage in largemouth bass.

The Potential of Marine Microalgae for the Production of Food, Feed, and Fuel (3F)

Whole-cell microalgae biomass and their specific metabolites are excellent sources of renewable and alternative feedstock for various products. In most cases, the content and quality of whole-cell biomass or specific microalgal metabolites could be produced by both fresh and marine microalgae strains. However, a large water footprint for freshwater microalgae strain is a big concern, especially if the biomass is intended for non-food applications. Therefore, if any marine microalgae could produce biomass of desired quality, it would have a competitive edge over freshwater microalgae. Apart from biofuels, recently, microalgal biomass has gained considerable attention as food ingredients for both humans and animals and feedstock for different bulk chemicals. In this regard, several technologies are being developed to utilize marine microalgae in the production of food, feed, and biofuels. Nevertheless, the production of suitable and cheap biomass feedstock using marine microalgae has faced several challenges associated with cultivation and downstream processing. This review will explore the potential pathways, associated challenges, and future directions of developing marine microalgae biomass-based food, feed, and fuels (3F).

The Effect of Sargassum siliquastrum Supplementation on Growth Performance, Cecal Fermentation, Intestine Histomorphology, and Immune Response of Japanese Quails

This study aimed to investigate the dietary effects of Sargassum siliquastrum on the growth performance, nutrient digestibility, cecal fermentation, microbial populations, antioxidant status, immune response, and intestine histomorphology of Japanese quails. A total of 450 Japanese quails, aged 7 days, weighing 27.35 ± 0.23 g, were randomly distributed to three dietary groups in a 42-day feeding experiment. Five replicates were prepared per group, with each replicate consisting of 30 chicks in a cage. The three dietary groups consisted of a basal diet (0% supplementation, which was the control) and diets supplemented with 1% and 2% of S. siliquastrum. The results showed that the S. siliquastrum-supplemented groups and the control group had a similar final body weight (FBW), average body gain (ADG), and average feed intake (ADFI). However, the S. siliquastrum-supplemented groups had a better feed conversion ratio (FCR), as well as a lower mortality rate, compared to the control group. S. siliquastrum supplementation improved the nutrient digestibility of dry matter (DM), organic matter (OM), crude proteins (CP), and crude fibers (CF) (p < 0.05). The S. siliquastrum-supplemented groups exhibited the heaviest empty intestine and cecum weights, as well as the longest intestinal and cecal lengths. Furthermore, the total volatile fatty acids (TVFA) and the propionic acid concentrations increased significantly in quails fed S. siliquastrum-supplemented diets (p < 0.05), although the concentration of NH3-N decreased (p < 0.05). The dietary inclusion of S. siliquastrum had a beneficial effect on cecal microbial populations, where the Lactobacillus sp. counts increased, and the E. coli and Clostridium perfringens counts decreased. The histopathological examination of the duodenum confirmed that S. siliquastrum dietary supplementation enhanced the height and width of the villi. Quails fed S. siliquastrum-supplemented diet exhibited the highest total antioxidant capacity, superoxide dismutase, glutathione peroxidase, and glutathione reductase activities, but the thiobarbituric acid reactive substance was decreased (p < 0.05). Serum IgA, IgG, and IgM concentrations increased considerably (p < 0.05) in S. siliquastrum-supplemented groups. In conclusion, S. siliquastrum supplementation in the diet of Japanese quail can provide beneficial effects on performance, cecal fermentation, beneficial bacteria populations, and the immune response, and could be considered as an alternative feed additive in poultry production.

Antiviral Activities of Algal-Based Sulfated Polysaccharides

An antiviral agent is urgently needed based on the high probability of the emergence and re-emergence of future viral disease, highlighted by the recent global COVID-19 pandemic. The emergence may be seen in the discovery of the Alpha, Beta, Gamma, Delta, and recently discovered Omicron variants of SARS-CoV-2. The need for strategies besides testing and isolation, social distancing, and vaccine development is clear. One of the strategies includes searching for an antiviral agent that provides effective results without toxicity, which is well-presented by significant results for carrageenan nasal spray in providing efficacy against human coronavirus-infected patients. As the primary producer of sulfated polysaccharides, marine plants, including macro- and microalgae, offer versatility in culture, production, and post-isolation development in obtaining the needed antiviral agent. Therefore, this review will describe an attempt to highlight the search for practical and safe antiviral agents from algal-based sulfated polysaccharides and to unveil their features for future development.

Fishmeal Dietary Replacement Up to 50%: A Comparative Study of Two Insect Meals for Rainbow Trout (Oncorhynchus mykiss)

The demand of optimal protein for human consumption is growing. The Food and Agriculture Organization (FAO) has highlighted aquaculture as one of the most promising alternatives for this protein supply gap due to the high efficiency of fish growth. However, aquaculture has been facing its own sustainability problem, because its high demand for protein has been traditionally satisfied with the use of fishmeal (FM) as the main source. Some of the most promising and sustainable protein substitutes for FM come from insects. The present manuscript provides insight into an experiment carried out on rainbow trout (Oncorhynchus mykiss) with a 50% replacement of FM with different larvae insect meals: Hermetia illucens (HI), and Tenebrio molitor (TM). TM showed better results for growth, protein utilization and more active digestive function, supported by intestinal histological changes. Liver histology and intermediary metabolism did not show relevant changes between insect meals, while other parameters such as antioxidant enzyme activities and tissue damage indicators showed the potential of insect meals as functional ingredients.

Removal of nitrate and phosphate from simulated agricultural runoff water by Chlorella vulgaris

Microalgae such Chlorella vulgaris can effectively absorb nitrate and phosphate from contaminated water. This work characterized nitrate and phosphate removal from simulated agricultural runoff using C. vulgaris. Statistically designed experiments were used to model the following responses: (1) algal growth; (2) nitrate removal; (3) phosphate removal; (4) protein in the algal biomass; (5) chlorophyll content of the biomass; (6) the biomass phenolics content; and (7) the free radical scavenging antioxidant activity of the biomass. These response were modelled for the following key experimental factors: initial nitrate concentration in the simulated runoff (1080-3240 mg L^-1, as NaNO₃), initial phosphate concentration (20-60 mg L^-1, as K₂HPO₄), photoperiod (8-24 h of light/day) and culture duration (5-15 days). The validated models were used to identify the factor levels to maximize the various responses. Nitrate removal was maximized at 85.6% when initial nitrate and phosphate concentrations were 2322 mg L^-1 and 38 mg L^-1 (N:P atom ratio ≈ 125:1), respectively, with a 17.2 h daily photoperiod in a 13-day culture. Phosphate removal was maximized at 95% when the initial nitrate and phosphate concentrations were 1402 mg L^-1 and 56.7 mg L^-1 (N:P ≈ 51:1), respectively, with a 15.7 h daily photoperiod in a 14.7-day culture. At least ~14 h of a daily photoperiod and a ~11-day culture period were required to maximize all the studied responses. C. vulgaris is edible and may be used as animal feed. Nutritional aspects of the biomass were characterized. Biomass with more than 24% protein could be produced. Under the best conditions, the chlorophyll (potential food colorants) content of the biomass was 8.5% and the maximum level of total phenolics (antioxidants) in the biomass was nearly 13 mg gallic acid equivalent g^-1.

Nanomagnetic approach applied to microalgae biomass harvesting: advances, gaps, and perspectives

Microalgae biomass is a versatile option for a myriad of purposes, as it does not require farmable land for cultivation and due of its high CO₂ fixation efficiency during growth. However, biomass harvesting is considered a bottleneck in the process because of its high cost. Magnetic harvesting is a promising method on account of its low cost, high harvesting speed, and efficiency, which can be used to improve the results of other harvesting methods. Here, we present the state of the art of the magnetic harvesting method. Detailed approaches involving different nanomaterials are described, including types, route of synthesis, and functionalization, variables that interfere with harvesting, and recycling methods of nanoparticles and medium. In addition to discussing the overall perspectives of the method, we provide a guideline for future research.