The aim of this work was to obtain biodiesel (methyl esters) from the saponifiable lipids (SLs) fraction of the
microalga Nannochloropsis gaditana, whose biomass dry weight contains 12.1 wt% of these lipids. SLs were extracted
from the microalga as free fatty acids (FFAs) for subsequent transformation to methyl esters (biodiesel) by enzymatic
esterification. Extraction as FFAs rather than as SLs allows them to be obtained with higher purity. Microalgal FFAs were
obtained by direct saponification of lipids in the biomass and subsequent extraction-purification with hexane. Esterification
of FFAs with methanol was catalysed by lipase Novozym 435 from Candida antarctica. Stability studies of this
lipase in the operational conditions showed that the esterification degree (ED) attained with the same batch of lipase
remained constant over six reaction cycles (36 h total reaction time). The optimal conditions attained for 4 g of FFAs
were 25C, 200 rpm, methanol/FFA molar ratio of 1.5:1, Novozym 435/FFA ratio of 0.025:1 w/w and 4 h reaction time. In
these conditions the ED attained was 92.6%, producing a biodiesel with 83 wt% purity from microalgal FFAs. Several
experimental scales were tested (from 4 to 40 g FFAs), and in all cases similar EDs were obtained.
The aim of this work was to obtain biodiesel (methyl esters) from the saponifiable lipids (SLs) fraction of themicroalga Nannochloropsis gaditana, whose biomass dry weight contains 12.1 wt% of these lipids. SLs were extractedfrom the microalga as free fatty acids (FFAs) for subsequent transformation to methyl esters (biodiesel) by enzymaticesterification. Extraction as FFAs rather than as SLs allows them to be obtained with higher purity. Microalgal FFAs wereobtained by direct saponification of lipids in the biomass and subsequent extraction-purification with hexane. Esterificationof FFAs with methanol was catalysed by lipase Novozym 435 from Candida antarctica. Stability studies of thislipase in the operational conditions showed that the esterification degree (ED) attained with the same batch of lipaseremained constant over six reaction cycles (36 h total reaction time). The optimal conditions attained for 4 g of FFAswere 25C, 200 rpm, methanol/FFA molar ratio of 1.5:1, Novozym 435/FFA ratio of 0.025:1 w/w and 4 h reaction time. Inthese conditions the ED attained was 92.6%, producing a biodiesel with 83 wt% purity from microalgal FFAs. Severalexperimental scales were tested (from 4 to 40 g FFAs), and in all cases similar EDs were obtained.
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