What this work is about, in plain words
Which is better for the bottom-dwelling diatom Cylindrotheca closterium: growing it in batches or in continuous-flow mode, where the medium is constantly renewed? The authors compared both methods and calculated the growth parameters needed to design installations.
Microalgae can be grown in batches: inoculate, wait for the crop and harvest it. Another way is continuous flow: fresh medium is fed in continuously, and part of the culture is withdrawn just as continuously. The authors compared these regimes on the diatom Cylindrotheca closterium and studied what a two-stage scheme gives, in which the culture passes through two vessels in series.
The experiments were run in the laboratory in two 3 L flat glass photobioreactors connected in series, at constant temperature and light. The feed rate of fresh medium was varied to see how the culture responds.
According to the authors, productivity in continuous-flow mode was 2.2 times higher than in batch growth. The one-stage and two-stage schemes reached their highest productivity at the same dilution rate: about 1.35 and 1.50 g of dry weight per liter per day. The authors also calculated how much silicon the culture needs for growth and how its growth depends on this element.
Engineers need these values: they are used to calculate regimes and sizes of installations for intensive cultivation of diatoms.
Limitations. Laboratory experiments in small reactors under constant conditions. In large volumes and under natural light, the figures may differ.