Reaction engineering analysis of Scenedesmus ovalternus in a flat-plate gas-lift photobioreactor

Microalgal strains of the genus Scenedesmus are a promising resource for commercial biotechnological applications. The temperature-, pH- and light-dependent growth of Scenedesmus ovalternus has been investigated on a laboratory scale. Best batch process performance was obtained at 30 °C, pH 8.0 and an incident photon flux density of 1300 μmol photons m⁻² s⁻¹ using a flat-plate gas-lift photobioreactor. Highest growth rate (0.11 h⁻¹) and space-time yield (1.7 ± 0.1 g_CDW L⁻¹ d⁻¹) were observed when applying these reaction conditions. Biomass concentrations of up to 7.5 ± 0.1 g_CDW L⁻¹ were achieved within six days (25.0 ± 0.5 g_CDW m⁻² d⁻¹). The light-dependent growth kinetics of S. ovalternus was identified using Schuster's light transfer model and Andrews’ light inhibition model (K_S = 545 μmol photons m⁻² s⁻¹; K_I = 2744 μmol photons m⁻² s⁻¹; μ_max = 0.21 h⁻¹). The optimal mean integral photon flux density for growth of S. ovalternus was estimated to be 1223 μmol photons m⁻² s⁻¹.