2.4. Optimization of lipids accumulation and productivity in
shallow ponds in Fortaleza simulated-climate
Short cultivation cycles under nutrients replete conditions, resulted in
low accumulation levels of lipids (Table S1, Supporting information and
Figures 3 and 5). Thus, to analyze the impact of nutrients depletion on
lipids productivity, we simulated cultures of S. obliquus C1S
supplemented with 2% CO2 (v/v) and 6 mM
NaNO3 in 5-cm deep ponds in Fortaleza, in winter, in
longer cultivation cycles. These cultures reached the stationary phase
of growth in 3 days (Figure 6a) and a biomass concentration of 2 g ·
L-1. The biomass became enriched in lipids from an
initial value of less than 10% (w/w) to 20% (w/w) at the onset of the
stationary phase and continued increasing up to a final value of 46%
(w/w) at the 7th day of culture (Figure 6b). The
analysis of the time course of areal biomass productivity showed a
maximum value around the second day (Figure 6c). Conversely, the maximum
lipid productivity resulting from cell proliferation and the induction
of lipid accumulation presented a relatively constant value around 5 g ·
m-2 · d-1 between days 2 and 5 of
culture (Figure 6d).