Productivity of Chlorella sorokiniana in a short light-path (SLP) panel photobioreactor under high irradiance

Abstract

Maximal productivity of a 14 mm light-path panel photobioreactor under high irradiance was determined. Under continuous illumination of 2100 μmol photons m-2 s-1 with red LEDs (light emitting diodes) the effect of dilution rate on photobioreactor productivity was studied. The light intensity used in this work is similar to the maximal irradiance on a horizontal surface at latitudes lower than 37º. Chlorella sorokiniana, a fast-growing green microalga, was used as a reference strain in this study. The dilution rate was varied from 0.06 h-1 to 0.26 h-1. The maximal productivity was reached at a dilution rate of 0.24 h-1, with a value of 7.7 g of dry weight m-2 h-1 (m2 of illuminated photobioreactor surface) and a volumetric productivity of 0.5 g of dry weight L-1 h- 1. At this dilution rate the biomass concentration inside the reactor was 2.1 g L-1 and the photosynthetic efficiency was 1.0 g dry weight per mol photons. This biomass yield on light energy is high but still lower than the theoretical maximal yield of 1.8 g mol photons-1 which must be related to photosaturation and thermal dissipation of absorbed light energy.