Evaluation of Microalgae as Immunostimulants and Recombinant Vaccines for Diseases Prevention and Control in Aquaculture

Chlamydomonas reinhardtii chloroplast factory construction for formate bioconversion

The photosynthetic autotrophic production of microalgae is limited by the effective supply of carbon and light energy, and the production efficiency is lower than the theoretical value. Represented by methanol, C1 compounds have been industrially produced by artificial photosynthesis with a solar energy efficiency over 10%, but the complexity of artificial products is weak. Here, based on a construction of chloroplast factory, green microalgae Chlamydomonas reinhardtii CC137c was modified for the bioconversion of formate for biomass production. By screening the optimal combination of chloroplast transport peptides, the cabII-1 cTP1 fusion formate dehydrogenase showed significant enhancement on the conversion of formate with a better performance in the maintenance of light reaction activity. This work provided a new way to obtain bioproducts from solar energy and CO2 with potentially higher-than-nature efficiency by the artificial-natural hybrid photosynthesis.

Screening of Microalgae for Bioactivity with Antiviral, Antibacterial, Anti-Inflammatory and Anti-Cancer Assays

Marine microalgae are a rich reservoir of natural compounds, including bioactives. Nonetheless, these organisms remain fairly unexplored despite their potential biotechnological applications. Culture collections with diverse taxonomic groups and lifestyles are a good source to unlock this potential and discover new molecules for multiple applications such as the treatment of human pathologies or the production of aquaculture species. In the present work extracts from thirty-three strains (including twenty dinoflagellates, four diatoms and nine strains from seven other algal classes), cultivated under identical conditions, were examined for their antiviral, antibacterial, anti-inflammatory and anti-cancer activities. Among these, antiviral and anti-inflammatory activities were detected in a few strains while the antibacterial tests showed positive results in most assays. In turn, most trials did not show any anti-cancer activity. Significant differences were observed between species within the same class, in particular dinoflagellates, which were better represented in this study. These preliminary findings pave the way for an in-depth characterization of the extracts with highest signals in each test, the identification of the compounds responsible for the biological activities found and a further screening of the CCVIEO culture collection.

Oral Administration of Antimicrobial Peptide NZ2114 Through the Microalgal Bait Tetraselmis subcordiformis (Wille) Butcher for Improving the Immunity and Gut Health in Turbot (Scophthalmus maximus L.)

Antibiotics are widely used in aquaculture to treat the bacterial diseases. However, the improper use of antibiotics could lead to environmental pollution and development of resistance. As a safe and eco-friendly alternative, antimicrobial peptides (AMPs) are commonly explored as therapeutic agents. In this study, a mutant strain of Tetraselmis subcordiformis containing AMP NZ2114 was developed and used as an oral drug delivery system to reduce the use of antibiotics in turbot (Scophthalmus maximus) aquaculture. The gut, kidney, and liver immune-related genes and their effects on gut digestion and bacterial communities in turbot fed with NZ2114 were evaluated in an 11-day feeding experiment. The results showed that compared with the group fed with wild-type T. subcordiformis, the group fed with T. subcordiformis transformants containing NZ2114 was revealed with decreased levels of both pro-inflammatory factors (TNF-α and IL-1β), inhibitory effect on Staphylococcus aureus, Vibrio parahaemolyticus, and Vibrio splendidus demonstrated by the in vitro simulation experiments, and increased richness and diversity of the gut microbiota of turbot. In conclusion, our study provided a novel, beneficial, and low-cost method for controlling bacteria in turbot culture through the oral drug delivery systems.

Effect of dietary inclusion of microalgae (Nannochloropsis gaditana and Schizochytrium spp) on non-specific immunity and erythrocyte maturity in Atlantic salmon fingerlings

The parr-smolt transformation in salmonids involves a critical period characterized by systemic changes associated with the fish's immune response. In this context, as a dietary ingredient in functional diets, microalgae offer an alternative due to their nutritional and bioactive compounds that could strengthen the immune status. This study evaluated the effect of a diet supplemented with Schizochytrium spp and Nannochloropsis gaditana on the expression of genes associated with the antibacterial response. Additionally, the study assessed the effect on the leukocyte population and erythrocyte maturity in Salmo salar blood. Fish were fed for 30 days with a microalgal mixture (1:1) at a 10% inclusion. Each diet was randomly assigned to a tank using a completely randomized design (CRD) with four replications. Each tank was stocked with 70 Atlantic salmon fingerlings with an initial mean weight of 78.87 ± 0.84. Transcription levels were quantified and analyzed by qRT-PCR from cell isolates and mucus tissue. Furthermore, cell count and identification of leukocytes and classification of cellular maturity of erythrocytes using a neural network with a multilayer perceptron (MLP) were performed. Our results showed a significant (p < 0.05) increase in fold change expression of C3 (2.54 ± 0.65) and NK-Lysine (6.84 ± 0.94) in erythrocytes of microalgae-supplemented fish. Moreover, a significant increase of 1.59 and 2.35 times in monocytes and immature erythrocytes, respectively, was observed in the same group of fish (p < 0.05). This study's results indicate that dual microalgae (Schizochytrium spp and N. gaditana) supplementation can increase innate humoral antibacterial components, particularly in erythrocyte tissue, and increase phagocytic cells and immature erythrocytes in S. salar blood.

Spray Drying Is a Viable Technology for the Preservation of Recombinant Proteins in Microalgae

Microalgae are promising host organisms for the production of encapsulated recombinant proteins such as vaccines. However, bottlenecks in bioprocess development, such as the drying stage, need to be addressed to ensure feasibility at scale. In this study, we investigated the potential of spray drying to produce a recombinant vaccine in microalgae. A transformant line of Chlamydomonas reinhardtii carrying a subunit vaccine against salmonid alphavirus was created via chloroplast engineering. The integrity of the recombinant protein after spray drying and its stability after 27 months storage at -80 °C, +4 °C and room temperature were assessed by immunoblotting. The protein withstood spray drying without significant losses. Long-term storage at +4 °C and room temperature resulted in 50% and 92% degradation, respectively. Optimizing spray drying and storage conditions should minimize degradation and favour short-term storage at positive temperatures. Using data on yield and productivity, the economics of spray drying- and freeze drying-based bioprocesses were compared. The drying stage corresponded to 41% of the total production cost. Process optimization, genetic engineering and new market strategies were identified as potential targets for cost reduction. Overall, this study successfully demonstrates the suitability of spray drying as a process option for recombinant protein production in microalgae at the industrial scale.

Overexpression of 18S rRNA methyltransferase CrBUD23 enhances biomass and lutein content in Chlamydomonas reinhardtii

Post-transcriptional modification of nucleic acids including transfer RNA (tRNA), ribosomal RNA (rRNA) and messenger RNA (mRNA) is vital for fine-tunning of mRNA translation. Methylation is one of the most widespread post-transcriptional modifications in both eukaryotes and prokaryotes. HsWBSCR22 and ScBUD23 encodes a 18S rRNA methyltransferase that positively regulates cell growth by mediating ribosome maturation in human and yeast, respectively. However, presence and function of 18S rRNA methyltransferase in green algae are still elusive. Here, through bioinformatic analysis, we identified CrBUD23 as the human WBSCR22 homolog in genome of the green algae model organism Chlamydonomas reinhardtii. CrBUD23 was a conserved putative 18S rRNA methyltransferase widely exited in algae, plants, insects and mammalians. Transcription of CrBUD23 was upregulated by high light and down-regulated by low light, indicating its role in photosynthesis and energy metabolism. To characterize its biological function, coding sequence of CrBUD23 fused with a green fluorescence protein (GFP) tag was derived by 35S promoter and stably integrated into Chlamydomonas genome by glass bead-mediated transformation. Compared to C. reinhardtii wild type CC-5325, transgenic strains overexpressing CrBUD23 resulted in accelerated cell growth, thereby leading to elevated biomass, dry weight and protein content. Moreover, overexpression of CrBUD23 increased content of photosynthetic pigments but not elicit the activation of antioxidative enzymes, suggesting CrBUD23 favors growth and proliferation in the trade-off with stress responses. Bioinformatic analysis revealed the G1177 was the putative methylation site in 18S rRNA of C. reinhardtii CC-849. G1177 was conserved in other Chlamydonomas isolates, indicating the conserved methyltransferase activity of BUD23 proteins. In addition, CrTrm122, the homolog of BUD23 interactor Trm112, was found involved in responses to high light as same as CrBUD23. Taken together, our study revealed that cell growth, protein content and lutein accumulation of Chlamydomonas were positively regulated by the 18S rRNA methyltransferase CrBUD23, which could serve as a promising candidate for microalgae genetic engineering.

The Plant Viruses and Molecular Farming: How Beneficial They Might Be for Human and Animal Health?

Plant viruses have traditionally been studied as pathogens in the context of understanding the molecular and cellular mechanisms of a particular disease affecting crops. In recent years, viruses have emerged as a new alternative for producing biological nanomaterials and chimeric vaccines. Plant viruses were also used to generate highly efficient expression vectors, revolutionizing plant molecular farming (PMF). Several biological products, including recombinant vaccines, monoclonal antibodies, diagnostic reagents, and other pharmaceutical products produced in plants, have passed their clinical trials and are in their market implementation stage. PMF offers opportunities for fast, adaptive, and low-cost technology to meet ever-growing and critical global health needs. In this review, we summarized the advancements in the virus-like particles-based (VLPs-based) nanotechnologies and the role they played in the production of advanced vaccines, drugs, diagnostic bio-nanomaterials, and other bioactive cargos. We also highlighted various applications and advantages plant-produced vaccines have and their relevance for treating human and animal illnesses. Furthermore, we summarized the plant-based biologics that have passed through clinical trials, the unique challenges they faced, and the challenges they will face to qualify, become available, and succeed on the market.

Oral administration of Synechococcus sp. PCC7942 trans-vp19 and trans-vp (19+28) genes improve the immune and antioxidant capacity in Procambarus clarkii under white spot syndrome virus stress

This study aimed to evaluate antioxidant capacity and protection from white spot syndrome virus (WSSV) challenge of Procambarus clarkii fed trans-vp19 and trans-vp (19 + 28) genes of Synechococcus sp. PCC7942 (Syn7942). P. clarkii were fed transgenic cyanobacteria continuously for 7 days, and then infected with WSSV after 12 h starvation. The daily mortality in each group was measured for 10 days and hepatopancreas and muscle of P. clarkii were examined for enzymes phenoloxidase (PO) activity, catalase (CAT) activity, glutathione peroxidase (GSH-px) activity, and malondialdehyde (MDA) concentration after immunization and viral challenge at different times. Compared with the WSSV-infected crayfish in positive control group (challenge and no vaccination) and wild type group (challenge, feeding wild-type Syn7942), vp19 group (challenge, feeding Syn7942 trans-vp19 gene) and vp (19 + 28) group [challenge, feeding Syn7942 trans-vp (19 + 28) genes] significantly improved the survival rate from 0% to 60% and 56.7%, respectively. Consistently, significantly greater PO, CAT, and GSH-px activity and significantly lower MDA concentration in the vp19 and vp (19 + 28) groups compared to the control group. These results demonstrate that the trans-vp19 and trans-vp (19 + 28) gene of Syn7942 significantly facilitated the immune and antioxidant capacity of crayfish. Therefore, the trans-vp19 and trans-vp (19 + 28) genes of Syn7942 could provide protection for crayfish as an anti-WSSV oral medication.

Foliar Spray or Soil Drench: Microalgae Application Impacts on Soil Microbiology, Morpho-Physiological and Biochemical Responses, Oil and Fatty Acid Profiles of Chia Plants under Alkaline Stress

Alkaline soil inhibits the growth and productivity of chia plants (Salvia hispanica L.). Microalgae as biofertilizers have been reported to induce alkalinity tolerance and enhance yield and quality. However, limited information is known concerning the influence of microalgae application on medical plants, including chia. Our experiments were performed to evaluate the effect of microalgae strains of Arthrospira platensis, Chlorella vulgaris, Nostoc muscorum, and Anabaena azollae with two application methods, foliar spray and soil drench, on morpho-physiological and biochemical parameters, yield, seed and oil quality, and fatty acid profiles of chia plants cultivated under alkaline soil conditions, as well as the on soil microbial activity. The results obtained reveal that both application methods positively influenced the growth and productivity of chia plants. However, the foliar application showed significant differences in the herb's fresh and dry weights and leaf pigments, whereas the drenching application caused more effect than the foliar spray application at the reproductive stage. Untreated chia plants showed a slight decline in the growth, productivity, and antioxidant level with an increase in Na content. However, microalgae applications significantly ameliorated these impacts as they induced an enhancement in the growth, leaf pigments, total protein and carbohydrate contents, nutrient content, seed and oil yields, as well as an increase in linolenic and linoleic fatty acids, with a reduction in saturated fatty acids, namely, palmitic and lauric acid. Soil drenching generated an improvement in the soil microbial activity and caused a reduction in the pH. The treatment of A. platensis with drenching application resulted in higher seed and oil yield, with an increase of 124 and 263.3% in seed and oil yield, respectively.

Assessment of Amphora coffeaeformis and Scenedesmus dimorphus algae as immunostimulant agents on Biomphlaria alexandrina snails against Schistosoma mansoni

Schistosoma mansoni is the main factor of human schistosomiasis which is responsible for high rates of mortality. Recently, the use of alternative biological control agents has gained importance in disease control because the intensive use of molluscicides is very harmful to human health and poses risks to the environment. In the present work, the potential effect of two freshwater algae, Amphora coffeaeformis and Scenedesmus obtusus, on the immune response of Biomphalaria alexandrina snails against infection with S. mansoni was investigated. Two different concentrations 1 and 2 g L− 1 from each dried algal material were tested on snails before exposure to miracidial infection by one day. The use of Amphora coffeaeformis has a greater immunostimulatory effect than Scendesmus obtusus at a low concentration of 1.0 g L− 1. The tested algae affected the snail’s hemocytes and its immune response to S. mansoni as evidenced by a significant decrease in infection rate and cercariae production. In addition, increasing in total hemocyte count, the formation of vacuoles, the appearance of several pseudopodia, and the formation of coarse granules in hemocytes of infected snails treated with A. coffeaeformis. Intense tissue reactions were also observed. In conclusion, it was confirmed that these algae can be used as an immunostimulant in the prevention and control of S. mansoni.

Current status and development prospects of aquatic vaccines

Diseases are a significant impediment to aquaculture's sustainable and healthy growth. The aquaculture industry is suffering significant financial losses as a result of the worsening water quality and increasing frequency of aquatic disease outbreaks caused by the expansion of aquaculture. Drug control, immunoprophylaxis, ecologically integrated control, etc. are the principal control strategies for fish infections. For a long time, the prevention and control of aquatic diseases have mainly relied on the use of various antibiotics and chemical drugs. However, long-term use of chemical inputs not only increases pathogenic bacteria resistance but also damages the fish and aquaculture environments, resulting in drug residues in aquatic products, severely impeding the development of the aquaculture industry. The development and use of aquatic vaccines are the safest and most effective ways to prevent aquatic animal diseases and preserve the health and sustainability of aquaculture. To give references for the development and implementation of aquatic vaccines, this study reviews the development history, types, inoculation techniques, mechanisms of action, development prospects, and challenges encountered with aquatic vaccines.

Novel protein carrier system based on cyanobacterial nano-sized extracellular vesicles for application in fish

Aquaculture has been one of the fastest‐growing food industry sectors, expanding at the pace of consumers' demands. To promote safe and effective fish growth performance strategies, and to stimulate environmentally friendly solutions to protect fish against disease outbreaks, new approaches are needed to safeguard fish welfare, as well as farmers and consumers interests. Here, we tested the use of cyanobacterial extracellular vesicles (EVs) as a novel nanocarrier system of heterologous proteins for applications in fish. We started by incubating zebrafish larvae with Synechocystis sp. PCC6803 EVs, isolated from selected mutant strains with different cell envelope characteristics. Results show that Synechocystis EVs are biocompatible with fish larvae, regardless of their structural composition, as EVs neither induced fish mortality nor triggered significant inflammatory responses. We establish also that cyanobacteria are amenable to engineering heterologous protein expression and loading into EVs, for which we used the reporter sfGFP. Moreover, upon immersion treatment, we successfully demonstrate that sfGFP‐loaded Synechocystis EVs accumulate in the gastrointestinal tract of zebrafish larvae. This work opens the possibility of using cyanobacterial EVs as a novel biotechnological tool in fish, with prospective applications in carrying proteins/enzymes, for example for modulating their nutritional status or stimulating specific adaptive immune responses.

Changes in immune genes expression, immune response, digestive enzymes -antioxidant status, and growth of catla (Catla catla) fed with Astragalus polysaccharides against edwardsiellosis disease

The effect of four level of Astragalus polysaccharides (APs) supplementation diets, (CD: control diet and three experiment diet (E), EA: 100 mg kg^-1 APs; EB: 200 mg kg-1 APs; EC: 300 mg kg^-1 APs) on growth, changes in haemato-biochemical parameters and metabolic-digestive enzymes, enhancement of antioxidant activity, innate-adaptive immune response, and cytokine gene expression were studied in catla (Catla catla) against Edwardsiella tarda. The healthy and challenged groups fed the CD displayed no mortality, while fish fed EA or EC revealed 10% mortality, but the mortality was only 5% in diet EB. Fish fed diet EB and EC revealed significantly better growth rates and high RBC count during the experimental period. Albumin and globulin levels were significant improved when fish were fed the diet EB and EC from weeks 6-8. The superoxide dismutase (SOD) was significant ameliorated by EB feeding from weeks 4-8. In contrast, serum myeloperoxidase (MPO), catalase (CAT), malondialdehyde (MDA)/lipid peroxidation (LPO), glutathione peroxidase (GPx), respiratory burst activity (RBA), bactericidal action (BCA), serum lysozyme activity (SLA), nitric oxide synthase (NOS), head kidney leukocytes response proliferation (HKLP), hemolytic action (HLA), hydrogen peroxides (H₂O₂), and immunoglobulin (Ig) were significantly improved from week 6-8. Groups fed the APs enriched diets had significant ameliorated interleukin (IL)-1β and interferon (IFN)-γ mRNA expression after 6 and 8 weeks of feeding. However, IL-10 and major histocompatibility complex (MHC)-1 mRNA expressions were significant enhanced in catla fed all APs diets on week 8. APs enriched diets revealed significant improved tumor necrosis factor (TNF)-α and TNF receptor-associated factor-6 (TRAF6) mRNA expression on week 4, but toll-like receptor-2 (TLR2) and TLR4 mRNA expression were significant enhanced by diet EB and EC after weeks 6 and 8. Similarly, the lysozyme (Lyz)-C and Lyz-G mRNA levels in the head kidney (HK) increased by APs feeding on weeks 6 and 8, whereas the EB diet, the expression of nucleotide binding oligomerization domain-1 (NOD1) was significantly improved on weeks 6 and 8, but NOD2 mRNA expression was only significant enhanced after 8 weeks of diet EB. By feeding healthy catla and E. tarda challenged fish fed diet EB, resulted in significantly increased growth, haemato-biochemical indices, metabolic-digestive enzymes, antioxidant activities, innate-adaptive immune responses, and cytokine gene expression mainly between 6 and 8 weeks.

In Vitro Antibacterial Activity of Marine Microalgae Extract against Vibrio harveyi

Marine microalgae may produce antibacterial substances. At the exponential phase of growth, four species of marine microalgae were examined for their potential to create secondary metabolites that limit the growth of Vibrio harveyi: Nannochloropsis oceanica, Chaetoceros gracilis, Isochrysis sp., and Thalassiosira weissflogii. V. harveyi is a pathogenic bacteria that can cause severe mortality and loss in aquaculture. Disc diffusion assay and co-culture assay were used to determine antibacterial activity. On TSA % NaCl media, the disc impregnated with microalgae and extracted with ethanol, methanol, saline water, and dimethyl sulfoxide (DMSO) was tested against V. harveyi at concentrations of 1.0 × 105, 106 and 107 CFU mL−1. The disc diffusion assay revealed that N. oceanica extracted with ethanol had the largest inhibitory zone against V. harveyi. Meanwhile, only N. oceanica, Isochrysis sp., and T. weissflogii reduced the growth of V. harveyi (105 CFU mL−1) in the co-culture assay (p < 0.05). The current findings reveal that the hydrophilic chemicals in microalgae extract have antibiotic activity against the highly virulent V. harveyi, which causes vibriosis, a serious disease in farmed fish and aquaculture cultivation around the world.

Dietary supplementation with microalgae enhances the zebrafish growth performance by modulating immune status and gut microbiota

Microalgae are known to be abundant in various habitats around the globe, and are rich in high value-added products such as fatty acids, polysaccharides, proteins, and pigments. Microalgae can be exploited as the basic and primitive food source of aquatic animals. We investigated the effects of dietary supplementation with Schizochytrium sp., Spirulina platensis, Chloroella sorokiniana, Chromochloris zofingiensis, and Dunaliella salina on the growth performance, immune status, and intestinal health of zebrafish (Danio rerio). The results showed that these five microalgae diets could improve the feed conversion rate (FCR), especially the D. salina (FCR = 1.02%) and Schizochytrium sp. (FCR = 1.20%) additive groups. Moreover, the microalgae diets decreased the gene expression level of the pro-inflammatory cytokines IL6, IL8, and IL1β at a normal physiological state of the intestine, especially the Schizochytrium sp., S. platensis, and D. salina dietary groups. The expression of neutrophil marker b7r was increased in the C. sorokiniana diet group; after, the zebrafish were challenged with Vibrio anguillarum, improving the ability to resist this disease. We also found that microalgae diets could regulate the gut microbiota of fish as well as increase the relative abundance of probiotics. To further explain, Cetobacterium was significantly enriched in the S. platensis additive group and Stenotrophomonas was higher in the Schizochytrium sp. additive group than in the other groups. Conversely, harmful bacteria Mycoplasma reduced in all tested microalgae diet groups. Our study indicated that these microalgae could serve as a food source supplement and benefit the health of fish. KEY POINTS: • Microalgae diets enhanced the growth performance of zebrafish. • Microalgae diets attenuated the intestinal inflammatory responses of zebrafish. • Microalgae diets modulated the gut microbiota composition to improve fish health.

β-glucan as a promising food additive and immunostimulant in aquaculture industry

The use of antibiotics in aquatic feed reduces the incidence of disease and enhances growth performance, although it presents harmful effects, such as development of resistant bacteria and accumulation in the natural environment. A variety of immune stimulants including probiotics, prebiotics, synbiotics, phytobiotics, organic acids, nucleotides, antioxidants, microalgae, yeast and enzymes have been used in the aquaculture industry. In recent decades, much attention has been paid on finding a variety of immunostimulants with lower cost which also affect specific and non-specific immunity and improve fish resistance against a wide range of pathogens. These stimulants strengthen the fish’s immune system by increasing the number of phagocytes, lysozyme activity and level of immunoglobulin. The use of immune stimulants as an effective tool to overcome diseases and strengthen the immune system of farmed species, leads to the promotion of cellular and humoral defense mechanisms and increases resistance to infectious diseases. Among these immunostimulants used in aquaculture, β-glucans are of particular importance. Glucans are complex polysaccharide compounds extracted from the cell wall of yeasts and fungi. These compounds can stimulate fish growth, survival, and immune function. Therefore, this review discusses the role and importance of β-glucan as a food additive in aquaculture and examines the impact of these compounds on the growth performance, immunity and biochemical parameters of farmed species.

Plant-Produced Vaccines: Future Applications in Aquaculture

Aquaculture has undergone rapid development in the past decades. It provides a large part of high-quality protein food for humans, and thus, a sustainable aquaculture industry is of great importance for the worldwide food supply and economy. Along with the quick expansion of aquaculture, the high fish densities employed in fish farming increase the risks of outbreaks of a variety of aquatic diseases. Such diseases not only cause huge economic losses, but also lead to ecological hazards in terms of pathogen spread to marine ecosystems causing infection of wild fish and polluting the environment. Thus, fish health is essential for the aquaculture industry to be environmentally sustainable and a prerequisite for intensive aquaculture production globally. The wide use of antibiotics and drug residues has caused intensive pollution along with risks for food safety and increasing antimicrobial resistance. Vaccination is the most effective and environmentally friendly approach to battle infectious diseases in aquaculture with minimal ecological impact and is applicable to most species of farmed fish. However, there are only 34 fish vaccines commercially available globally to date, showing the urgent need for further development of fish vaccines to manage fish health and ensure food safety. Plant genetic engineering has been utilized to produce genetically modified crops with desirable characteristics and has also been used for vaccine production, with several advantages including cost-effectiveness, safety when compared with live virus vaccines, and plants being capable of carrying out posttranslational modifications that are similar to naturally occurring systems. So far, plant-derived vaccines, antibodies, and therapeutic proteins have been produced for human and animal health. However, the development of plant-made vaccines for animals, especially fish, is still lagging behind the development of human vaccines. The present review summarizes the development of fish vaccines currently utilized and the suitability of the plant-production platform for fish vaccine and then addresses considerations regarding fish vaccine production in plants. Developing fish vaccines by way of plant biotechnology are significant for the aquaculture industry, fish health management, food safety, and human health.

Physicochemical Evaluation of Edible Cyanobacterium Arthrospira platensis Collected from the South Atlantic Coast of Morocco: A Promising Source of Dietary Supplements

The cyanobacterium Arthrospira platensis (A. platensis)—a genus of nonheterocystous filamentous cyanobacteria—is used in industrial applications and as a food supply. The current research work aims to study the physicochemical characteristics of A. platensis indigenous to the Moroccan Atlantic coast at Laayoune (Foum El Oued lagoon). The contents of proteins, carbohydrates, vitamins, lipids, minerals, heavy metals, energy value, humidity, ash, pigments, and tannins in A. platensis were investigated using protocols as described in the earlier literature. The values of protein, carbohydrate, and lipid contents in A. platensis were 58.9 ± 0.07, 14.67, and 45.54% respectively. The values of vitamins B₂ and B₃ dosed in A. platensis were 1.31 ± 0.19 and 30.8 ± 0.001 mg/kg, respectively. The values of heavy metals including lead and chromium were 70 ± 4.5 and 5 ± 0.5 PPB (parts-per-billion), respectively; however, no trace concerning cadmium was detected. The values of energy value, humidity, and ash content were 346.48 ± 0.21, 11.6 ± 0.17%, and 9.1 ± 0.21% kcal/100 g, respectively. The results of pigment content showed the presence of chlorophyll b, chlorophyll a, and carotenoids of 37.506 ± 3.38, 26.066 ± 3.08, and 9.52 ± 0.22 mg/g, respectively. The results obtained revealed that A. platensis indigenous to the Moroccan Atlantic coast at Laayoune was found to be very rich in proteins, carbohydrates, vitamins, minerals, ash, and pigments and lower in heavy metals and saturated fats when compared with species investigated in the literature. Thus, A. platensis indigenous to the Moroccan Atlantic coast at Laayoune fulfills the requirements for being used as dietary supplements.

Efficient Transient Expression of Recombinant Proteins Using DNA Viral Vectors in Freshwater Microalgal Species

The increase in the world population, the advent of new infections and health issues, and the scarcity of natural biological products have spotlighted the importance of recombinant protein technology and its large-scale production in a cost-effective manner. Microalgae have become a significant promising platform with the potential to meet the increasing demand for recombinant proteins and other biologicals. Microalgae are safe organisms that can grow rapidly and are easily cultivated with basic nutrient requirements. Although continuous efforts have led to considerable progress in the algae genetic engineering field, there are still many hurdles to overcome before these microorganisms emerge as a mature expression system. Hence, there is a need to develop efficient expression approaches to exploit microalgae for the production of recombinant proteins at convenient yields. This study aimed to test the ability of the DNA geminiviral vector with Rep-mediated replication to transiently express recombinant proteins in the freshwater microalgal species Chlamydomonas reinhardtii and Chlorella vulgaris using Agrobacterium-mediated transformation. The SARS-CoV-2 receptor binding domain (RBD) and basic fibroblast growth factor (bFGF) are representative antigen proteins and growth factor proteins, respectively, that were subcloned in a geminiviral vector and were used for nuclear transformation to transiently express these proteins in C. reinhardtii and C. vulgaris. The results showed that the geminiviral vector allowed the expression of both recombinant proteins in both algal species, with yields at 48 h posttransformation of up to 1.14 μg/g RBD and 1.61 ng/g FGF in C. vulgaris and 1.61 μg/g RBD and 1.025 ng/g FGF in C. reinhardtii. Thus, this study provides a proof of concept for the use of DNA viral vectors for the simple, rapid, and efficient production of recombinant proteins that repress the difficulties faced in the genetic transformation of these unicellular green microalgae. This concept opens an avenue to explore and optimize green microalgae as an ideal economically valuable platform for the production of therapeutic and industrially relevant recombinant proteins in shorter time periods with significant yields.