Enzymatic biodiesel production by hydroesterification using waste cooking oil as feedstock

Biodiesel production was investigated by hydroesterification using enzymatic catalysis in both hydrolysis and esterification reactions. Soybean oil resulting from food frying processes (WCO) was used as feedstock. Lipase from Geotrichum candidum was produced by submerged fermentation and used without prior purification as biocatalyst in WCO hydrolysis, which was optimized using a factorial design. A complete hydrolysis of WCO (44.1% mass fraction) was obtained after 80 min of reaction at 40 degrees C, performed in an emulsifier-free system with no buffer (40 degrees C and 900 rpm). In a subsequent step, FFA obtained from the hydrolysis reaction were esterified (40 degrees C, 200 rpm) using ethanol as acyl-acceptor (1:1.5) and Pseudomonas fluorescens lipase (PFL) immobilized on styrene-divinylbenzene (SDB) as biocatalyst (15% m/v). This biocatalyst was recycled for 6 cycles with no significant activity losses. The biodiesel composition was found by gas chromatography, and proton nuclear magnetic resonance (1H NMR) spectra and Fourier transform infrared spectroscopy (FTIR) were used to verify the quality and purity of biodiesel. Enzymatic biodiesel achieved FAEE content of 94.1 +/- 0.5% and no traces of monoacyglycerol (MAG), diacylglycerol (DAG), triacylglycerol (TAG) or free glycerol were observed, indicating that the hydroesterification route produced high-quality biodiesel, despite the fact that WCO was used as feedstock.