High-added value products from microalgae and prospects of aquaculture wastewaters as microalgae growth media

Abstract

Aquaculture plays an important role in human nutrition and economic development but is often expanded to the detriment of the natural environment. Several research projects, aimed at cultivating microalgae in aquaculture wastewaters (AWWs) to reduce organic loads and minerals, along with the production of microalgal cell mass and metabolic products, are underway. Microalgal cell mass is of high nutritional value and is regarded as a candidate to replace, partially at least, the fish meal in the fish feed. Also, microalgal cell mass is considered as a feedstock in the bio-fuel manufacture, as well as a source of high-added value metabolic products. The production of these valuable products can be combined with the reuse of AWWs in the light of environmental concerns related with the aquaculture sector. Many research papers published in the last decade demonstrate that plenty of microalgae species are able to efficiently grow in AWWs, mainly derived from fish and shrimp farms, and produce valuable metabolites reducing the AWW pollutant load. We conclude that bio-remediation of AWWs combining with the production of microalgae cell mass and specific metabolites is probably the most convenient and economical solution for AWWs management and can contribute to the sustainable growth of the aquaculture.

A Novel Recirculating Aquaculture System for Sustainable Aquaculture: Enabling Wastewater Reuse and Conversion of Waste-to-Immune-Stimulating Fish Feed

“…Therefore, other microorganisms known for producing polyunsaturated fatty acids (PUFAs) such as microalgae and fungi − could be employed in RAS-PHB and serve as a feed supplement. PUFAs, particularly eicosapentaenoic and docosahexaenoic acids, are known to be essential supplements in the aquaculture feed as they can improve fish health and the quality of seafood produced (e.g., increased omega-3 content in the seafood). ,, In this context, our proposed RAS-PHB system is still an optimal technology as the system can be further expanded and generalized for cultivating other microbial biomasses such as PUFA-producing microalgae under mixotrophic conditions (i.e., autotrophic and heterotrophic). ,, Previous studies have reported successful cultivations of different PUFA-rich microalgal strains using fish farm effluents under nonsterile conditions. , However, such an approach was limited by the low lipid content (25%) and low biomass yields (usually <400–850 mg/L) in the cultivated PUFA-producing microorganisms. , …”

“…25,74,75 In this context, our proposed RAS-PHB system is still an optimal technology as the system can be further expanded and generalized for cultivating other microbial biomasses such as PUFA-producing microalgae under mixotrophic conditions (i.e., autotrophic and heterotrophic). 71,76,77 Previous studies have reported successful cultivations of different PUFA-rich microalgal strains using fish farm effluents under nonsterile conditions. 75,76 However, such an approach was limited by the low lipid content (25%) and low biomass yields (usually <400−850 mg/L) in the cultivated PUFA-producing microorganisms.…”

“…71,76,77 Previous studies have reported successful cultivations of different PUFA-rich microalgal strains using fish farm effluents under nonsterile conditions. 75,76 However, such an approach was limited by the low lipid content (25%) and low biomass yields (usually <400−850 mg/L) in the cultivated PUFA-producing microorganisms. 71,75 Finally, the use of chitosan in SCP harvesting can be considered remedial and safe for fish consumption, as it is obtained from crab and shrimp wastes.…”

Optimizing Microalgal Biomass Feedstock Selection for Nanocatalytic Conversion Into Biofuel Clean Energy, Using Fuzzy Multi-Criteria Decision Making Processes

“…• Nannochloropsis sp. : that demonstrates a considerable fatty acid profile especially when using magnetic harvesting (Savvidou et al, 2020) and when it is cultivated in aquaculture wastewaters (Ansari et al, 2017;Dourou et al, 2020).…”

Effect of Dietary Tryptophan on Growth, Intestinal Microbiota, and Intestinal Gene Expression in an Improved Triploid Crucian Carp

“…Improving the growth rate and feed conversion rate of fish is essential for the sustainable development of aquaculture (1,2). Amino acids play important roles in the nutrient metabolism of cultured fishes.…”