RESUMEN
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.
Asunto(s)
Microalgas , Estramenopilos , Fotobiorreactores , Porosidad , Biomasa , LuzRESUMEN
The microalga Haematococcus pluvialis is mainly cultivated in suspended systems for astaxanthin production. Immobilized cultivation on a Twin-Layer porous substrate photobioreactor (TL-PSBR) has recently shown promise as an alternative approach. In Vietnam, a TL-PSBR was constructed as a low-angle (15 °) horizontal system to study the cultivation of H. pluvialis for astaxanthin production. In this study, the biomass and astaxanthin productivities and astaxanthin content in the dry biomass were determined using different initial biomass (inoculum) densities (from 2.5 to 10 g dry weight m-2), different storage times of the initial biomass at 4 °C (24, 72, 120 and 168 h) and different light intensities (300-1000 µmol photons m-2 s-1). The optimal initial biomass density at light intensities between 400-600 µmol photons-2 s-1 was 5-7.5 g m-2. Algae stored for 24 h after harvest from suspension for immobilization on the TL-PSBR yielded the highest biomass and astaxanthin productivities, 8.7 g m-2 d-1 and 170 mg m-2 d-1, respectively; longer storage periods decreased productivity. Biomass and astaxanthin productivities were largely independent of light intensity between 300-1000 µmol photons m-2 s-1 but the efficiency of light use per mole photons was highest between 300-500 µmol photons m-2 s-1. The astaxanthin content in the dry biomass varied between 2-3% (w/w). Efficient supply of CO2 to the culture medium remains a task for future improvements of angled TL-PSBRs.