What this work is about, in plain words
The authors isolated the small diatom Nanofrustulum shiloi from fouling off the Black Sea coast, described it and grew it in the laboratory as a dense culture. They measured the growth rate and the share of protein, lipids, omega-3 acids and fucoxanthin in the biomass.
Diatoms accumulate valuable substances: the orange pigment fucoxanthin and long-chain omega-3 fatty acids. But almost all industrial technologies are built on planktonic species. Bottom-dwelling and near-bottom diatoms are less studied, although they have a useful property: the cells settle on their own, which makes harvesting biomass easier. The authors searched among Black Sea diatoms for such a species and assessed whether it is suitable for biotechnology.
N. shiloi was found in fouling on polymer materials off the Black Sea coast. A pure culture was obtained from single cells and described under light and electron microscopes, then grown in a flat 2 L laboratory photobioreactor with air bubbling. A standard nutrient medium was compared with a medium containing five times more nutrients.
According to the authors, on the enriched medium culture density reached 1.27 g dry weight per liter, against 0.32 g/L on the standard one. The specific growth rate was 0.8 per day, and the highest productivity was 0.46 g/(L·day). At the start of the stationary phase, the biomass contained about 20 % lipids and 43 % protein, 10 mg/g dry weight of fucoxanthin and 67 mg/g of polyunsaturated fatty acids, with eicosapentaenoic acid (omega-3) the most abundant. When mixing was switched off, the cells settled quickly.
The work describes a Black Sea culture of this species as a possible source of fucoxanthin and omega-3 acids.
Limitations. This is a laboratory experiment in a 2 L volume with one growth cycle. The authors did not test whether the species is suitable for large volumes.