The extraction experiments performed with the untreated microalgae
showed very poor lipid extraction capability of n-hexane, both at 40 °C
(0.2%) and 60 °C (2.4%). On the other hand, the amounts of n-hexane
extractable lipid improved as a result of applying the steam explosion
technique before extracting the lipid from the microalgae. Steam exploded
samples without acid impregnation presented lipid yields varying
from 2.5% to 4.4%, depending on the steam explosion temperature and
solvent extraction temperature. As it was expected, increasing the temperature
resulted in higher values of lipid yield. However, the benefits
of using higher temperature should be carefully considered for large
scale application, as it may be a large energy burden for the whole process.
Another temperature-related issue that must be taken into account
is the possible degradation of byproducts such as proteins and other labile
compounds.