The mechanism of lipid extraction from marine microalgae
by ethanol are not yet well understood. According to the
aforementioned experimental results and all those references
reported,22,34 the possible mechanism was illustrated in Figure
6. Ethanol diffuses easily through the cell membrane into the
cytoplasm and interacts with the cellular lipids. Since the algal
cells are distorted with pits and gaps, the cellular lipids may be
extracted from the distorted cells quickly. Additionally, for
some membrane-associated lipids, which are strongly linked
with proteins in the cell membrane, ethanol can disrupt
membrane-based lipid−protein associations and form hydrogen
bonds with membrane-associated lipids.22 Then the lipids are
dissolved into the ethanol phase and dissociated away from the
cell membrane in a way similar to that of the cellular lipids. On
the other hand, cell lysis is also a mechanism of lipid extraction.
The cellular contents, such as lipids, may be released directly
into ethanol from disrupted cells. However, the mechanism
may be secondary since the cell disruption efficiencies of
marine microalgae tested in this study were relatively low with
19−25%. Therefore, we speculated that the lipids in the