Optimisation of T-ISO
biomass production rich in essential fatty acids
II. Effect of different
light regimes on the production of fatty acids
I.
Tzovenis, N. De Pauw, P. Sorgeloos-2003
Aquaculture, 216(1-4): 223-242
Abstract:
It is well documented that culture conditions affect
the fatty acid content of microalgae. We report in this study the fatty acid
profiles and n-3 HUFA productivity of T-ISO, a popular haptophyte in
the aquaculture industry, cultured under three photoperiods (24:0, 16:08 and
12:12 h L:D) combined with three photon flux densities (PFD: 120, 220 and
460 µmol photon m-2 s-1), at 25 °C. Sampling took
place in both the exponential and post-exponential (light-limited) phase.
In general, fatty acid proportions were effected by a
strong interaction of L:D×PFD resulting in metabolic changes difficult to
be modelled. At the 12:12 and 24:0 h L:D the fatty acid pattern can be
summarised as PUFA>SAFA>MUFA, while at 16:08 h L:D as
SAFA>PUFA>MUFA reflecting a differential acclimation of the strain
under light–dark cycles. At the 12:12 h L:D the PUFA content of biomass
was significantly higher than at the other photocycles. PUFA content
differences were located in the n-3 fraction with the n-6
content being rather constant. The n-3/n-6 and DHA/EPA ratios
under 24:0 h or 12:12 h L:D were optimal according to the literature for
fish and shellfish nutrition requirements. In contrast, the 16:08 h L:D
regimes, especially at low PFD, produced inadequate ratios.
The production of n-3 HUFA in T-ISO is
essentially influenced by the total photon flux available per day in a
similar manner with growth. The capacity of the strain for storing lipid is
limited under the conditions tested; consequently, the fatty acid content
follows the biomass yield and productivity pattern. Hence, in the context of
aquaculture a light regime of 12:12 h L:D and a PFD within the
photolimitation–photoinhibition range offers advantages for the culture of
T-ISO. If the high investment could be substantiated, continuous cultures
under 24:0 h L:D at the same PFD range could serve as an optimisation basis
using advanced photobioreactors.
(Department of Ecology and Systematics, Faculty of
Biology, University of Athens, Panepistimioupolis, Zografou 15784, Greece.
Tel.: +30-1-7274042; fax: +30-1-7274885; email: itzoveni@eexi.gr)