Conclusions This work studied the enzymatic production of
biodiesel by esterification of FFAs from UVO and the microalga N.
gaditana. Saponifiable lipids (SLs) were first extracted from
microalgal biomass as FFAs, which allows them to be obtained with
a high degree of purity (73.5 wt%), because microalgal FFAs are
easier to purify than microalgal SLs. Novozym 435 from C. antarctica
was chosen to catalyse this esterification due its high activity (or ED
attained) and its high stability in the reaction conditions. Although
no solvent was used, the ED obtained in six reactions (of 2 and 6 h
each), catalysed with the same batch of lipase, remained constant.
The optimal conditions for the esterfication of FFAs with methanol
were established with FFAs from UVO and the maximum ED
attained was reproduced with FFAs from the microalga N. gaditana
(92.6%). These optimal conditions are: 1.5:1 methanol/FFA molar
ratio, 25C, stirring at 200 rpm (with 4 g of FFAs), IOT ¼ 0.1 g
Novozym 435 h/g FFAs (for example 0.1 g Novozym 435 and 4 h
for 4 g of FFAs). This IOT is much lower than that required to produce
biodiesel from microalgal lipids, because the esterification of
FFAs occurs much faster than the transesterification of SLs. Moreover,
the biodiesel obtained from FFAs is purer (78.6 wt%) than that
obtained from lipids. The enzymatic catalysis of the esterification of
FFAs to produce biodiesel also consumes less methanol and energy
than acid catalysis
Conclusions This work studied the enzymatic production ofbiodiesel by esterification of FFAs from UVO and the microalga N.gaditana. Saponifiable lipids (SLs) were first extracted frommicroalgal biomass as FFAs, which allows them to be obtained witha high degree of purity (73.5 wt%), because microalgal FFAs areeasier to purify than microalgal SLs. Novozym 435 from C. antarcticawas chosen to catalyse this esterification due its high activity (or EDattained) and its high stability in the reaction conditions. Althoughno solvent was used, the ED obtained in six reactions (of 2 and 6 heach), catalysed with the same batch of lipase, remained constant.The optimal conditions for the esterfication of FFAs with methanolwere established with FFAs from UVO and the maximum EDattained was reproduced with FFAs from the microalga N. gaditana(92.6%). These optimal conditions are: 1.5:1 methanol/FFA molarratio, 25C, stirring at 200 rpm (with 4 g of FFAs), IOT ¼ 0.1 gNovozym 435 h/g FFAs (for example 0.1 g Novozym 435 and 4 hfor 4 g of FFAs). This IOT is much lower than that required to producebiodiesel from microalgal lipids, because the esterification ofFFAs occurs much faster than the transesterification of SLs. Moreover,the biodiesel obtained from FFAs is purer (78.6 wt%) than thatobtained from lipids. The enzymatic catalysis of the esterification ofFFAs to produce biodiesel also consumes less methanol and energythan acid catalysis
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