Stochastic analysis of algal-cell motion

Yair Zarmi

Single-cell algae are mass-produced as an income source for modern desert settlers. The algae can grow in relatively low-quality water, which is recycled. In large ponds, the optimal biomass production rate cannot be improved. However, in thin bioreactors (containers that can be meters long and high, but a few cm thick), the optimal rate increases by about one order of magnitude. Light hits the transparent wall of the container. As the density of algae is extremely high, only a thin layer near the illuminated wall is exposed to light. Most of the cells are in the dark. They perform a random walk owing to turbulent motion induced in the water by passing air bubbles. The purpose of this research is to analyze the stochastic equations governing the motion of cells in and out of the illuminated layer, and find its effect on biomass productivity.

Further reading:

• Combined effects of Light Intensity, Light-Path and Culture Density on Output Rate of Spirulina platensis (Cyanobacteria) - Hu Qiang, Y. Zarmi & A. Richmond, Eur. J. Phycol., 33, 165-171 (1998).

• Biological Principles of Mass Cultivation - A. Richmond, pp. 125-177 in Handbook of Microalgal Culture (ed. A. Richmond), Blackwell, Oxford 2004.