pure glycerol and crude glycerol being used in the medium,
respectively. As shown in Fig. 1A, the cells grew very well in
crude glycerol compared with glucose and pure glycerol. The
cell dry weight reached the highest level in day 5–6. For all
three cultures, there were still relatively high levels of residual
glucose or glycerol when the cells ceased growth (Fig. 1B). The
reason may be that the nitrogen sources used here (1 g/L
tryptone and 1 g/L yeast extract) were lower than that reported
by Yokochi et al. [16] (20 g/L corn steep liquor). Thus, nitrogen
was the limiting factor when 90–75 g/L glucose or glycerol
were used. Cell growth kinetics and DHA production by S.
limacinum on different substrates were further compared
(Table 5). It was found that the specific cell growth rate,
maximum cell dry weight, and biomass productivity of the
crude glycerol-culture was higher than that of the pure glycerolculture.
The growth yield on glycerol (Yx/s) was lower than that
on glucose, suggesting the algal cells could utilize glucose more
efficiently for their growth. The DHA content of the three
cultures was similar, however, due to the low biomass in pure
glycerol culture, the DHAyield and productivity from the pure
glycerol–algal culture were lower than the other two cases.