Biomass and Astaxanthin Productivities of Haematococcus pluvialis in an Angled Twin-Layer Porous Substrate Photobioreactor: Effect of Inoculum Density and Storage Time

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 &deg
) 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&minus
2), different storage times of the initial biomass at 4 &deg
C (24, 72, 120 and 168 h) and different light intensities (300&ndash
1000 &micro
mol photons m&minus
2 s&minus
1). The optimal initial biomass density at light intensities between 400&ndash
600 &micro
mol photons&minus
1 was 5&ndash
7.5 g m&minus
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&minus
2 d&minus
1 and 170 mg m&minus
1, respectively
longer storage periods decreased productivity. Biomass and astaxanthin productivities were largely independent of light intensity between 300&ndash
1 but the efficiency of light use per mole photons was highest between 300&ndash
500 &micro
1. The astaxanthin content in the dry biomass varied between 2&ndash
3% (w/w). Efficient supply of CO2 to the culture medium remains a task for future improvements of angled TL-PSBRs.