Evaluation of the productive and physiological responses of Litopenaeus vannamei infected with WSSV and fed diets enriched with Dunaliella sp

Recent advances in microalgal production, harvesting, prediction, optimization, and control strategies

The market value of microalgae has grown exponentially over the past two decades, due to their use in the pharmaceutical, nutraceutical, cosmetic, and aquatic/animal feed industries. In particular, high-value products such as omega-3 fatty acids, proteins, and pigments derived from microalgae have high demand. However, the supply of these high-value microalgal bioproducts is hampered by several critical factors, including low biomass and bioproduct yields, inefficiencies in monitoring microalgal growth, and costly harvesting methods. To overcome these constraints, strategies such as synthetic biology, bubble generation, photobioreactor designs, electro-/magnetic-/bioflocculation, and artificial intelligence integration in microalgal production are being explored. These strategies have significant promise in improving the production of microalgae, which will further boost market availability of algal-derived bioproducts. This review focuses on the recent advances in these technologies. Furthermore, this review aims to provide a critical analysis of the challenges in existing algae bioprocessing methods, and highlights future research directions.

Chronic toxicity of shrimp feed added with silver nanoparticles (Argovit-4®) in Litopenaeus vannamei and immune response to white spot syndrome virus infection

In recent years, the application of silver nanoparticles (AgNPs) as antibacterial compounds has been widely used in human and veterinary medicine. In this work, we investigated the effects of AgNPs (Argovit-4®) as feed additives (feed-AgNPs) on shrimp (Litopenaeus vannamei) using three different methods: 1) chronic toxicity after 28 days of feeding, 2) Effects against white spot syndrome virus (WSSV) challenged by oral route, and 3) transcriptional responses of immune-related genes (PAP, ProPO, CTL-3, Crustin, PEN3, and PEN4) following WSSV infection. The results showed that the feed-AgNPs did not interfere with the growth and survival of shrimp. Also, mild lesions in the hepatopancreas were recorded, proportional to the frequency of the feed-AgNP supply. Challenge test versus WSSV showed that feeding every 7 days with feed-AgNPs reduced mortality, reaching a survival rate of 53%, compared to the survival rates observed in groups fed every 4 days, daily and control groups of feed-AgNPs for the 30%, 10%, and 7% groups, respectively. Feed-AgNPs negatively regulated the expression of PAP, ProPO, and Crustin genes after 28 days of treatment and altered the transcriptional responses of PAP, ProPO, CTL-3, and Crustin after WSSV exposure. The results showed that weekly feeding-AgNPs could partially prevent WSSV infection in shrimp culture. However, whether or not transcriptional responses against pathogens are advantageous remains to be elucidated.

An overview of microalgae biomass as a sustainable aquaculture feed ingredient: food security and circular economy

Sustainable management of natural resources is critical to food security. The shrimp feed and fishery sector is expanding rapidly, necessitating the development of alternative sustainable components. Several factors necessitate the exploration of a new source of environmentally friendly and nutrient-rich fish feed ingredients. Microalgal biomass has the potential to support the growth of fish and shrimp aquaculture for global food security in the bio-economy. Algal biorefineries must valorize the whole crop to develop a viable microalgae-based economy. Microalgae have the potential to replace fish meal and fish oil in aquaculture and ensure sustainability standards. Microalgae biomasses provide essential amino acids, valuable triglycerides such as lipids, vitamins, and pigments, making them suitable as nutritional supplements in livestock feed formulations. Fish and microalgae have similar nutritional profiles, and digestibility is a critical aspect of the aquafeed formulation. A highly digestible feed reduces production costs, feed waste, and the risk of eutrophication. Due to low input costs, low carbon footprint, wastewater treatment benefits, and carbon credits from industrial CO₂ conversion, microalgae-based fish and shrimp feeds have the potential to provide significant economic benefits. However, several challenges must be addressed before microalgal biomass and bioproducts may be used as fish feeds, including heavy metal bioaccumulation, poor algal biomass digestion, and antinutrient effects. Knowledge of biochemical composition is limited and diverse, and information on nutritional value is scattered or contradictory. This review article presents alternative approaches that could be used in aquaculture to make microalgal biomass a viable alternative to fish meal.

Aquatic Plants and Aquatic Animals in the Context of Sustainability: Cultivation Techniques, Integration, and Blue Revolution

The aquaculture industry has rapidly increased in response to the increasing world population, with the appreciation that aquaculture products are beneficial for human health and nutrition. Globally, aquaculture organisms are mainly divided into two divisions, aquatic animals (finfish, crustaceans, and molluscs) and aquatic plants (microalgae and seaweed). Worldwide aquaculture production has reached more than 82 million tonnes (MTs) in 2018 with more than 450 cultured species. The development of economical, environmentally friendly, and large-scale feasible technologies to produce aquaculture organisms (even aquatic animals and/or aquatic plants) is an essential need of the world. Some aquaculture technologies are related to aquatic animals or aquatic plants, as well as some technologies have an integrated system. This integration between aquatic plants and aquatic animals could be performed during early larvae rearing, on-growing and/or mass production. In the context of the blue revolution, the current review focuses on the generations of integration between aquatic plants and aquatic animals, such as live feeds, biomass concentrates, water conditioners “green water technique”, aqua-feed additives, co-culturing technologies, and integrated multi-trophic aquaculture (IMTA). This review could shed light on the benefit of aquatic animals and plant integration, which could lead future low-cost, highly efficient, and sustainable aquaculture industry projects.

Physiological and antioxidant response of Litopenaeus vannamei against Vibrio parahaemolyticus infection after feeding supplemented diets containing Dunaliella sp. flour and β-glucans

The presence of pathogen agents in shrimp farming is the main obstacle for successful aquaculture. Vibrio species are naturally part of water because they play an important role as opportunistic bacteria. Vibrio parahaemolyticus was identified as the causative agent of the Early Mortality Syndrome in 2009, causing the loss of shrimp farming worldwide. Dunaliella sp. flour has been tested against Vibrio infection proving to be an effective prophylactic method that decreases mortality and improves physiological and immune response in Litopenaeus vannamei. Juvenile shrimp were exposed to 2% Dunaliella sp. flour and commercial 1.1% β -glucan diet provided every other day for 15 days and a posterior infection with V. parahaemolyticus (1 × 10⁶ CFU/mL). To evaluate shrimp stress status, some parameters as glucose, lactate, cholesterol, triglycerides, relative superoxide dismutase (SOD) gene expression and circulating hemocytes were analyzed in hemolymph at zero and seven days before infection and at 0, 24, and 48 h post-infection. L. vannamei fed with Dunaliella sp. showed 93% and β -glucan 87% survival, compared with 79% in the infected control group. Additionally, Dunaliella sp. improved hemocyte and lipid concentrations compared to β -glucan while both immunostimulants showed an increase in SOD response against bacteria. The addition of 2% Dunaliella sp. every other day in L. vannamei diet enhanced stress response against V. parahaemolyticus infection.

The dietary effect of fucoidan extracted from brown seaweed, Cystoseira trinodis (C. Agardh) on growth and disease resistance to WSSV in shrimp Litopenaeus vannamei

The polysaccharide-fucoidan plays a fundamental role in shrimp aquaculture by being used as a natural immunostimulant and dietary supplementation. In this study, Cystoseira trinodis fucoidan (FCT) was extracted, its structure was determined using FT-IR analysis, and its effect of fucoidan on growth performance and WSSV resistance in Litopenaeus vannamei was evaluated. Four experimental diets, including the control (without FCT), 0.1, 0.2, and 0.4% FCT, were formulated and fed to shrimps for 60 days. Next, they were exposed to WSSV, and their mortality rate was noted daily up to 20 days. The results of the growth experiment demonstrated a significant increase in the final weight, WG, and SGR, and a lower FCR in treatments than in control. During the challenge trial, 100% mortality was recorded in control within ten days. However, FCT-treated shrimps indicated a mortality increase from 43.33 to 75.00% during 20 days of infection. The immunological and biochemical parameters and the expression of immune-related genes in individuals fed the FCT-incorporated diet considerably (p < 0.01) improved over control before the challenge (0 days) and after the challenge on days 5, 10, 15, and 20. It was concluded that L. vannamei fed on diets supplemented with all concentrations of FCT (especially 0.4%) had improved the growth, immunological and biochemical parameters, and the expression of immune-related genes, as well as enhancing the resistance against WSSV.

Potential of microalgae as a sustainable feed ingredient for aquaculture

An increase in fish consumption, combined with a decrease in wild fish harvest, is driving the aquaculture industry at rapid pace. Today, farmed seafood accounts for about half of all global seafood demand for human consumption. As the aquaculture industry continues to grow, so does the market for aquafeed. Currently, some of the feed ingredients are coming from low-value forage fishes (fish meal) and terrestrial plants. The production of fish meal can't be increased as it would affect the sustainability and ecosystem of the ocean. Similarly, increasing the production of terrestrial plant-based feed leads to deforestation and increased freshwater use. Hence, alternative and environmentally sustainable sources of feed ingredients need to be developed. Microalgae biomasses represent potential feed source ingredients as the cell metabolites of these microorganisms contain a blend of essential amino acids, healthy triglycerides as fat, vitamins, and pigments. In addition to serving as bulk ingredient in aquafeed, their unique array of bioactive compounds can increase the survivability of farmed species, improve coloration and quality of fillet. Microalgae has the highest areal biomass productivities among photosynthetic organisms, including fodder crops, and thus has a high commercial potential. Also, microalgal production has a low water and arable-land footprint, making microalgal-based feed environmentally sustainable. This review paper will explore the potential of producing microalgae biomass as an ingredient of aquaculture feed.