Carlos Escudero-Oñate

NordAqua is a multidisciplinary Nordic Center of Excellence funded by NordForsk Bioeconomy program (2017–2022). The research center promotes Blue Bioeconomy and endeavours to reform the use of natural resources in a environmentally sustainable way. In this short communication, we summarize particular outcomes of the consortium. The key research progress of NordAqua includes (1) improving of photosynthetisis, (2) developing novel photosynthetic cell factories that function in a “solar‐driven direct CO₂ capture to target bioproducts” mode, (3) promoting the diversity of Nordic cyanobacteria and algae as an abundant and resilient alternative for less sustainable forest biomass and for innovative production of biochemicals, and (4) improving the bio‐based wastewater purification and nutrient recycling technologies to provide new tools for integrative circular economy platforms.

Calcium oxide (CaO), also known as burnt lime, is being considered as a possible treatment to reduce the negative impact of sea urchins on tare forests in northern coastal waters and blue-green algal blooms in the surrounding of fish-farms. In this respect, the reaction kinetics of burnt lime in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it “slaked” as CaO reacted with water to yield calcium hydroxide (Ca(OH)₂). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)₂), calcium sulphate dihydrate (gypsum, CaSO₄·2H₂O) and calcium carbonate (CaCO₃), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 h. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to <9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8.

The sorption equilibrium and thermodynamics of Cu(II), Ni(II), Pb(II), and Cd(II) onto grape stalks (GS), a lignocellulosic waste from wine production industries, have been investigated. Different equilibrium models have been assessed to describe the experimental sorption equilibrium profile in the range of 5–60°C. Maximum sorption capacities have been calculated by means of Langmuir equilibrium model and mean free sorption energies through the Dubinin-Radushkevich (D-R) model. Mean free energies suggest that metal sorption takes place mainly through an ion exchange mechanism, except for Pb(II), where an additional contribution connected to a stronger bond might take place. The calculation of thermodynamic parameters, ΔG0, ΔH0 and ΔS0, puts into evidence that the sorption of all the metals onto GS is a spontaneous and exothermic process that occurs with an increase of randomness at the solid/liquid interface.

In the last decades, an increasing attention has been directed toward the possibilities of growing algae commercially. This interest has been partially due to the fact that some strains of microalgae and cyanobacteria have demonstrated the ability to produce a variety of bioactive products. Both, primary and secondary metabolism of these microorganisms has been demonstrated to play a key role in the production of special chemicals. Antioxidants, for instance, can be produced by some algal strains to protect photosynthetic cells from oxidative stress. Microalgae can produce a variety of polyunsaturated and monounsaturated fatty acids with clear health benefits for human nutrition. Potential products obtained from cyanobacteria and microalgae exhibiting interesting medical properties include polysaccharides, glycerol, glycoproteins, and antibiotics. From the aforementioned products, especially relevant has become the search of new antibiotics. The potential spread of bacterial resistance and the foreseen decrease on efficiency on antibiotics, has largely stimulated the research on novel antibiotics sources. Among these sources, cyanobacteria and microalgae have demonstrated a vast and just barely explored potential.