Production of Ethyl Esters by Direct Transesterification of Microalga Biomass Using Propane as Pressurized Fluid

This work aimed to produce ethyl esters from Chlorella vulgaris microalgae biomass, using an immobilized enzymatic catalyst associated with pressurized fluid (propane) by direct transesterification. In order to optimize the ethyl conversion, different temperatures (46.7–68.1 °C) and pressures (59.5–200.5 bar) were applied a central composite design rotational (CCDR) obtaining the high conversion (74.39%) at 50 °C and 180 bar. The molar ratio also was investigated showing conversions ~ 90% using a molar ratio of 1:24 (oil:ethanol). From the best transesterification conditions, 50 °C, 180 bar, 20% enzymatic concentration, and 1:24 oil:ethanol molar ratio were obtained with success 98.9% conversion in 7 h of reaction. The enzyme reuse maintained its activity for three successive cycles. Thus, this simple process was effective to convert microalgal biomass into ethyl ester by direct transesterification and demonstrate high yields.