Esterification of FFAs catalysed by lipase Novozym 435 In this reaction
FFAs react with methanol to produce methyl esters (biodiesel) and water in the
presence of the lipase Novozym 435 which acts as catalyst. Experiments were carried
out with 4 g of FFAs, 0.86 mL of methanol (methanol/FFA molar ratio 1.5:1) and
different Novozym 435/FFA ratios. The esterification reaction was carried out in
50 mL Erlenmeyer flasks with silicone-capped stoppers. In a typical experiment the
mixture was incubated at 40C and stirred in an orbital shaking air-bath (Inkubator
1000, Unimax 1010 Heidolph, Klein, Germany) at 200 rpm for 24 h. The reactions
were stopped by separation of Novozym 435 by filtration. The final reaction mixture
was conserved at 4C until analysis. Experiments were carried out modifying the
following variables: reaction time, temperature, stirring velocity, methanol/FFA
molar ratio and Novozym 435 amount. All reactions and their corresponding analyses
were carried out in duplicate, and each value recorded is therefore the arithmetic
mean of four experimental data (data shown as mean value standard
deviation).