Optimising biomass and peridinin accumulation in the dinoflagellate Symbiodinium voratum using a twin-layer porous substrate bioreactor
Dinoflagellates are a natural source for unique secondary metabolites and pigments, which have considerable potential for applications in biomedical drug development and cosmetics. However, the technical cultivation of dinoflagellates in commonly used suspension-based closed photobioreactors (PBRs) has been shown to be difficult due to the sensitivity of the cultures to turbulence and shear forces. To overcome these and other constraints of suspension cultivation, immobilised cultivation of the dinoflagellate Symbiodinium voratum has been performed using a twin-layer porous substrate bioreactor (TL-PSBR). By optimising biomass growth using printing paper as substrate, a maximal biomass growth rate of 7.8 g dry weight m−2 growth area day−1 was measured over a period of 40 days at the relatively high-light intensity of 600 μmol photons m−2 s−1 and 2% (v/v) CO2. Linear growth of the S. voratum biofilm was observed over 40 days, and a maximal biomass standing crop of 305 g m−2 was gained. Synthesis of the potentially high-value carotenoid pigment peridinin, however, was favoured at low-light conditions (≤ 100 μmol photons m−2 s−1). By combining maximal biomass growth at high-light conditions with maximal peridinin accumulation at low-light conditions in a two-phase approach (14 days cultivation at 600 μmol photons m−2 s−1 and 2% CO2 followed by 14 days at 100 μmol photons m−2 s−1 and ambient air), a peridinin productivity of 51.4 mg peridinin m−2 day−1 was measured (about 30% higher than the values determined at either low- or high-light conditions). Using the two-phase approach, peridinin accumulated to a standing crop of ~ 1 g peridinin m−2 after 28 days of cultivation in a bench-scale TL-PSBR with a peridinin content in the dry biomass of 1% (w/w). Symbiodinium voratum may thus be a suitable source of peridinin for a diverse range of applications when grown in a twin-layer porous substrate bioreactor.
KeywordsDinoflagellate Symbiodinium Porous substrate bioreactor Peridinin Immobilised cultivation
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