New Angled Twin–layer Porous Substrate Photobioreactors for Cultivation of Nannochloropsis oculata

Abstract

An angled twin–layer porous substrate photobioreactor (TL-PSBR) using LED light was designed to cultivate Nannochloropsis oculata. Flocculation and sedimentation by modification of pH to 11 were determined as the optimal method for harvesting the N. oculata inoculum. The following optimised parameters were found: tilt angle 15°, Kraft 220 g m⁻² paper as substrate material, initial inoculum density of 12.5 g m⁻², 140 µmol photons m⁻² s⁻¹ light intensity, and a light/dark cycle of 6:6 (h). Test cultivation for 14 days was performed under optimised conditions. The total dried biomass standing crop was 75.5 g m⁻² growth area with an average productivity of 6.3 g m⁻² d⁻¹, the productivity per volume of used culture medium was 126.2 mg/L d⁻¹, total lipid content 21.9% (w/w), and the highest productivity of total lipids was 1.33 g m⁻² d⁻¹. The dry algal biomass contained 3% eicosapentaenoic acid (w/w), 3.7% palmitoleic acid (w/w), and 513 mg kg⁻¹ vitamin E. The optimisation of N. oculata cultivation on an angled TL-PSBR system yielded promising results, and applications for commercial products need to be further explored.