Figs. 2E–2H show the results for both microalgae lipids and both alcohols, where the best results were obtained using lipids extracted from N. gaditana and ethanol at 20 C at an alcohol to lipid ratio of 8:1 (v/v) (Fig. 2E and 2F). The FAAE yield of the N. gaditana lipids – methanol system was considerably lower than N. gaditana–ethanol system for all alcohol to lipid ratios. In the case of B. braunii lipids however, ethanol was found to be a poor acy acceptor and best results were found with methanol (Figs. 2G and 2H).
The effect of alcohol availability over the lipase performance in FAAE production process is well known. Alcohol normally is added stepwise in order to avoid the inhibition of the lipase [21]. In the case of the three phase bioreactor the alcohol dosage depend on the evaporation rate, where methanol has a higher vapor pressure than ethanol, 13.02 and 5.93 kPa, respectively (at 20 C) [22], indicating that at the same temperature methanol has a higher evaporation rate than ethanol, causing probably a higher enzyme inhibition. Additionally, in other lipase sources, the inhibition of the catalytic activity has proven to be higher in presence of methanol than in presence of ethanol [23]. This result could indicate that mass transfer has the most important role in this systems,due determine the grade of compounds availability to the fungi.