Extraction of FFAs from the microalga N. gaditana FFAs
from the microalga N. gaditana were extracted by the procedure
shown in Fig. 1, which is an adaptation to this microalga of a similar
process applied to the microalgae Phaeodactylum tricornutum (11)
and Isochrysis galbana (13). By this procedure 83.4 3.1 wt% of
fatty acids contained in the microalgal biomass were recovered
and these FFAs were extracted with 73.5 2.6 wt% purity. On the
other hand, saponifiable lipids (SLs) without transforming in FFAs
were also extracted in our laboratory by a similar two-step
process: (i) extraction of lipid from the wet microalgal biomass
with ethanol (96% v/v) and (ii) purification of these extracted
lipids by a second extraction with hexane. This method achieved
a similar SL recovery yield (85%), but the SL purity was only 31%,
the impurities consisting mainly of unsaponifiable lipids
(carotenoids), which obviously can not be transformed into
methyl esters (biodiesel). The transformation of SLs into FFAs by
direct saponification in the biomass (Fig. 1) allows easier
separation of FFAs and unsaponifiable lipids, and, therefore, a
higher purity of the final biodiesel. Besides, the extraction of SLs
as FFAs does not imply an excessive increasing of the economical
cost because only an alkali, as NaOH or KOH, have to be added to
the extraction solvent (ethanol) to transform SLs to FFAs.
The microalgal biodiesel obtained from the esterification reaction
was 78.6 1.3 wt% pure, which is similar to the purity of FFAs
extracted from microalgal biomass (73.5 2.6 wt%) following the
procedure shown in Fig. 1. This result highlights the fact that the
enzymatic conversion of FFAs to methyl esters does not reduce
biodiesel purity.
Extraction of FFAs from the microalga N. gaditana FFAsfrom the microalga N. gaditana were extracted by the procedureshown in Fig. 1, which is an adaptation to this microalga of a similarprocess applied to the microalgae Phaeodactylum tricornutum (11)and Isochrysis galbana (13). By this procedure 83.4 3.1 wt% offatty acids contained in the microalgal biomass were recoveredand these FFAs were extracted with 73.5 2.6 wt% purity. On theother hand, saponifiable lipids (SLs) without transforming in FFAswere also extracted in our laboratory by a similar two-stepprocess: (i) extraction of lipid from the wet microalgal biomasswith ethanol (96% v/v) and (ii) purification of these extractedlipids by a second extraction with hexane. This method achieveda similar SL recovery yield (85%), but the SL purity was only 31%,the impurities consisting mainly of unsaponifiable lipids(carotenoids), which obviously can not be transformed intomethyl esters (biodiesel). The transformation of SLs into FFAs bydirect saponification in the biomass (Fig. 1) allows easierseparation of FFAs and unsaponifiable lipids, and, therefore, ahigher purity of the final biodiesel. Besides, the extraction of SLsas FFAs does not imply an excessive increasing of the economicalcost because only an alkali, as NaOH or KOH, have to be added tothe extraction solvent (ethanol) to transform SLs to FFAs.The microalgal biodiesel obtained from the esterification reactionwas 78.6 1.3 wt% pure, which is similar to the purity of FFAsextracted from microalgal biomass (73.5 2.6 wt%) following theprocedure shown in Fig. 1. This result highlights the fact that theenzymatic conversion of FFAs to methyl esters does not reducebiodiesel purity.
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