Comparison among immobilised lipases on macroporous polypropylene toward biodiesel synthesis

Eight commercial lipases were characterised (protein content and specific activity) and immobilised on macroporous polypropylene via physical adsorption. The lipases showed a different level of adaptation to the support as determined by the comparison of their catalytic efficiencies (activity/loading). The immobilised lipases were compared toward methanolysis of vegetable oil to obtain biodiesel in solvent-free conditions. Immobilised Pseudomonas fluorescens lipase was the most active biocatalyst (ester yield = 58 mol% after 22 h), followed by immobilised Pseudomonas cepacia lipase (ester yield = 37 mol% after 51.5 h), whereas all the other lipases (from Rhizopus oryzae, Candida rugosa, Mucor javanicus, Penicillium roqueforti, Aspergillus niger, Penicillium camembertii), were inactive toward biodiesel synthesis. The effect of triglyceride feedstock, reaction temperature, water content, and enzyme loading was determined. Under the optimal conditions, i.e. soybean oil, T = 30 °C, water content = 0.5 mg water/mg of biocatalyst, loading = 600 mg lipase AK/g support, an ester yield of 98 mol% after 70 h was obtained.