Algae have been consumed for millennia in several parts of the world as food, food supplements, and additives, due to their unique organoleptic properties and nutritional and health benefits. Algae are sustainable sources of proteins, minerals, and fiber, with well-balanced essential amino acids, pigments, and fatty acids, among other relevant metabolites for human nutrition. This review covers the historical consumption of algae in Europe, developments in the current European market, challenges when introducing new species to the market, bottlenecks in production technology, consumer acceptance, and legislation. The current algae species that are consumed and commercialized in Europe were investigated, according to their status under the European Union (EU) Novel Food legislation, along with the market perspectives in terms of the current research and development initiatives, while evaluating the interest and potential in the European market. The regular consumption of more than 150 algae species was identified, of which only 20% are approved under the EU Novel Food legislation, which demonstrates that the current legislation is not broad enough and requires an urgent update. Finally, the potential of the European algae market growth was indicated by the analysis of the trends in research, technological advances, and market initiatives to promote algae commercialization and consumption.

Microalgal biomass represents a sustainable bioresource for various applications, such as food, nutraceuticals, pharmaceuticals, feed, and other bio-based products. For decades, its mass production has attracted widespread attention and interest. The process of microalgal biomass production involves several techniques, mainly cultivation, harvesting, drying, and pollution control. These techniques are often designed and optimized to meet optimal growth conditions for microalgae and to produce high-quality biomass at acceptable cost. Importantly, mass production techniques are important for producing a commercial product in sufficient amounts. However, it should not be overlooked that microalgal biotechnology still faces challenges, in particular the high cost of production, the lack of knowledge about biological contaminants and the challenge of loss of active ingredients during biomass production. These issues involve the research and development of low-cost, standardized, industrial-scale production equipment and the optimization of production processes, as well as the urgent need to increase the research on biological contaminants and microalgal active ingredients. This review systematically examines the global development of microalgal biotechnology for biomass production, with emphasis on the techniques of cultivation, harvesting, drying and control of biological contaminants, and discusses the challenges and strategies to further improve quality and reduce costs. Moreover, the current status of biomass production of some biotechnologically important species has been summarized, and the importance of improving microalgae-related standards for their commercial applications is noted.

To optimize fucoxanthin production in Tisochrysis lutea, the effect of different process parameters on fucoxanthin productivity (Pfx) were evaluated using batch and continuous experiments. In batch, the highest Pfx was found at 30 °C and 300 μmol m^-2 s^-1, allowing to design continuous experiments to optimize the dilution rate. The highest ever reported Pfx (9.43-9.81 mg L^-1 d^-1) was achieved at dilution rates of 0.53 and 0.80 d^-1. Irradiance was varied (50-500 μmol m^-2 s^-1) to result in a range of absorbed light between 2.23 and 25.80 mol m^-2 d^-1 at a fixed dilution rate (0.53 d^-1). These experiments validated the hypothesis that light absorbed can be used to predict fucoxanthin content, resulting in 2.23 mol m^-2 d^-1 triggering the highest fucoxanthin content (16.39 mg/g). The highest Pfx was found with 18.38 mol m^-2 d^-1. These results can be used to achieve high Pfx or fucoxanthin content during cultivation of Tisochrysis lutea.

The effect of light on biomass and fucoxanthin (Fx) productivities was studied in two microalgae, Tisochrysis lutea and Phaeodactylum tricornutum. High and low biomass concentrations (1.1 and 0.4 g L⁻¹) were tested in outdoor pilot‐scale flat‐panel photobioreactors at semi‐continuous cultivation mode. Fluorescence spectroscopy coupled with chemometric modeling was used to develop prediction models for Fx content and for biomass concentration to be applied for both microalgae species. Prediction models showed high R² for cell concentration (.93) and Fx content (.77). Biomass productivity was lower for high biomass concentration than low biomass concentration, for both microalgae (1.1 g L⁻¹: 75.66 and 98.14 mg L⁻¹ d⁻¹, for T. lutea and P. tricornutum, respectively; 0.4 g L⁻¹: 129.9 and 158.47 mg L⁻¹ d⁻¹, T. lutea and P. tricornutum). The same trend was observed in Fx productivity (1.1 g L⁻¹: 1.14 and 1.41 mg L⁻¹ d⁻¹, T. lutea and P. tricornutum; 0.4 g L⁻¹: 2.09 and 1.73 mg L⁻¹ d⁻¹, T. lutea and P. tricornutum). These results show that biomass and Fx productivities can be set by controlling biomass concentration under outdoor conditions and can be predicted using fluorescence spectroscopy. This monitoring tool opens new possibilities for online process control and optimization.

Many efforts have focused on the adsorption of metals from contaminated water by microbes. Synechococcus PCC7002, a major marine cyanobacteria, is widely applied to remove metals from the ocean’s photic zone. However, its ability to adsorb cesium (Cs) nuclides has received little attention. In this study, the biosorption behavior of Cs(I) from ultrapure distilled water by living Synechococcus PCC7002 was investigated based on kinetic and isotherm studies, and the biosorption mechanism was characterized by Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, and three-dimensional excitation emission matrix fluorescence spectroscopy. Synechococcus PCC7002 showed extremely high tolerance to Cs ions and its minimal inhibitory concentration was 8.6 g/L. Extracellular polymeric substances (EPS) in Synechococcus PCC7002 played a vital role in this tolerance. The biosorption of Cs by Synechococcus PCC7002 conformed to a Freundlich-type isotherm model and pseudo-second-order kinetics. The binding of Cs(I) was primarily attributed to the extracellular proteins in EPS, with the amino, hydroxyl, and phosphate groups on the cell walls contributing to Cs adsorption. The biosorption of Cs involved two mechanisms: Passive adsorption on the cell surface at low Cs concentrations and active intracellular adsorption at high Cs concentrations. The results demonstrate that the behavior and mechanism of Cs adsorption by Synechococcus PCC7002 differ based on the Cs ions concentration.

Microalgae are potential iron supplements for improving iron deficiency through an unknown mechanism. To analyze the increase in non-heme iron absorption caused by microalgae, six different microalgal feeds were prepared from Spirulina, Chlorella and Synechococcus sp. PCC 7002 as the main source of dietary iron (25 mg kg⁻¹; denoted as H-Sp, H-Ch, and H-Sy, respectively) or as a partial source of dietary iron (5 mg kg⁻¹; denoted as L-Sp, L-Ch, and L-Sy, respectively) to suppress iron-deficiency anemia in rats. The hemoglobin regeneration efficiencies in anemic rats were in the order ferric citrate (34.7 ± 1.8%) < H-Ch (49.9 ± 4.1%) ≈ H-Sy (50.6 ± 5.3%) ≈ L-Sp (46.9 ± 6.2%) ≈ L-Ch (43.1 ± 6.9%) ≈ L-Sy (43.5 ± 2.4%) ≈ FeSO₄ (47.2 ± 4.9%) < H-Sp (54.8 ± 5.5%). The percentage content of intestinal nanosized iron in the H-Sp, H-Ch, and H-Sy treatment groups was significantly higher than that in the L-Sp, L-Ch, and L-Sy groups, and was significantly higher in the microalgal diet groups than in the ferric citrate group, providing strong evidence for nanosized iron supplementation from microalgae. Overall, microalgae, especially Spirulina, are functional iron nutritive fortifiers that can supply intestinal nanosized iron.