Cultivation of Spirulina platensis in a combined airlift-tubular reactor system

This preliminary study aims at evaluating the efficiency of a bench-scale tubular photobioreactor by means of batch cultivations of Spirulina platensis under light-limited conditions. The most interesting feature of this plant configuration is the use of an airlift system for biomass re-cycling instead of traditional pumps to avoid the well-known problems of trichome damage owing to mechanical stress. A maximum cell concentration of 10.6 g l−1 was attained after 15 days of cultivation using a photosynthetic active radiation of 120 μmol photons m−2 s−1. Although the system operated in laminar flow under all the conditions investigated in this study, excess thricome stress was prevented only at relatively low air flow rates (<4.5 l min−1), corresponding to culture speeds lower than 0.21 m s−1.