Fig. 4

Optimization of the enzymatic process. Influence of reaction factors on the efficiency of BGTl-mediated hydrolysis of SGs (expressed as conversion %) in commercial soybean oil biodiesel/water mixtures. Experimental conditions: a 100:15 biodiesel/water mixtures, 5 µg of enzyme/g biodiesel, 70 °C, and 50 mM phosphate or citrate buffers of different pHs, b 100:15 biodiesel/water mixtures, 5 µg of enzyme/g biodiesel, 70 °C, phosphate buffer (pH 6.75) at different concentrations, c 100:15 biodiesel/water mixtures, 5 µg of enzyme/g biodiesel, 20 mM phosphate buffer (pH 6.75), 70 °C, and different concentrations of NaCl, d 100:15 biodiesel/water mixtures, 5 µg of enzyme/g biodiesel, 20 mM phosphate buffer (pH 6.75), 20 mM NaCl, at different temperatures, e 100:15 biodiesel/water mixtures, 20 mM phosphate buffer (pH 6.75), 20 mM NaCl, 65 °C, and different concentrations of BGTl, f biodiesel/water mixtures with different water content, 5 µg of enzyme/g biodiesel, 20 mM phosphate buffer (pH 6.75), 20 mM NaCl, 65 °C. Error bars show the standard deviation of three independent assays