3.2. Production of carotenoids from pure and raw glycerol
The growth and biosynthesis of total carotenoids by
S. ruberrimus H110, and also the consumption of glycerol, is presented
in Fig. 1. Until the 70th hour after inoculation, the microorganism
totally consumed the substrate and the maximum biomass
accumulation was achieved. The maximum accumulation of total
carotenoids was reached after 79 h for the batches containing
raw glycerol as carbon source, and after 95 h when pure glycerol
was used. These results indicate that the concentration of
carotenoids is not completely associated to biomass concentration,
especially during the initial and final stages of growth, as it can be
seen in Fig. 1. In fact there were differences in carotenoids
concentrations per biomass along time. For example, between 70
and 79 h of fermentation, the concentration of carotenoids per g
of biomass varied from 0.0203 to 0.0257 g g1 for pure glycerol,
from 0.0210 to 0.0303 g g1 for raw glycerol 1 and from 0.0250
to 0.0293 g g1 for raw glycerol 2. At 79 h of fermentation, the concentrations
of carotenoids per g of biomass were very similar
between the two types of raw glycerol, however the higher concentration
of biomass achieved in the presence of raw glycerol 1
contributed to the better result. Concentrations of carotenoids
were described, within the range [8 h; 95 h], by the polynomial
equations presented in Table 2.
The highest concentration of carotenoids (0.51 g L1) was
achieved when the raw glycerol 1 was used as the carbon source,
while the other samples contained a maximum of 0.4 g L1. This
difference of around 27% could be attributed to the higher content
of fatty acids in the raw glycerol 1 (Table 1). There were also significant
differences in maximum productivity when the raw glycerol
was used. Increases of 1.5 and 1.2 were observed for the raw
glycerol 1 and 2, respectively, in comparison to the pure glycerol.
When considering the maximum concentrations of carotenoids
predicted by the polynomial models, the value calculated for the
raw glycerol 1 was around 12% higher in relation to the one calculated
for the raw glycerol 2.