Production of ¹³C polyunsaturated fatty acids from the microalga Phaeodactylum tricornutum

F.G. Acién Fernández, C. Brindley Alias, J.A. Sánchez Pérez, J.M. Fernández Sevilla, M.J. Ibáñez González, E. Molina Grima-2003

Journal of Applied Phycology, 15(2): 229-237

Abstract:

An integrated process for the indoor production of ¹³C labelled PUFA from Phaeodactylum tricornutum is presented. The core of the process is a bubble column photobioreactor from which the exhaust gas from the reactor is returned to the culture by a low pressure compressor. To avoid accumulation of dissolved oxygen in the culture medium, the exhaust gas is bubbled through a sodium sulphite solution before returning it to the reactor. Carbon is removed from the medium before inoculating the alga, then labelled ¹³CO₂ is injected for pH control and carbon supply. The reactor has been operated in semicontinuous mode at a dilution rate of 0.01 h^-1, a biomass productivity of 0.1 g L^-1 d^-1 being obtained. Under this conditions both pH and dissolved oxygen were correctly controlled and the adequacy of the system for autotrophic production of labelled biomass was demonstrated. Analysis by GC-MS revealed that the fatty acids content of the biomass obtained was 10% d.wt., the content of eicosapentaenoic acid was 2.5% d.wt. All the fatty acids were labelled, more that 90% of the carbon present in these fatty acids was ¹³C. Element analysis of biomass and supernatant showed that 59.5% of injected carbon was assimilated into the biomass whereas 33% remained in the supernatant, and 7.5% remained undetected. Due to the high cost of ¹³CO₂ different strategies for the optimisation of labelled carbon use are proposed.

(Department of Chemical Engineering, University of Almería, Almería, E-04071, Spain, e-mail of E.M. Grima: emolina@ual.es)

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