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Biodiesel fuel (fatty acid methyl esters; FAMEs) can be produced by methanolysis of waste edible oil with a lipase. The degree of methanolysis was low in reaction systems so far reported, and the lipase catalyst could not be reused in spite of using immobilized enzyme. We clarified this problem was due to the irreversible inactivation of the lipase by contact with insoluble methanol (MeOH). Based on this result, we developed a stepwise methanolysis system with immobilized Candida antarctica lipase. Two-step batch methanolysis was most effective for the production of biodiesel fuel from waste oil: the first-step reaction was conducted in the presence of 1/3 molar equivalent of MeOH for the stoichiometric amount, and the second-step reaction was performed by adding 2/3 molar equivalent of MeOH. If the immobilized carrier is destroyed by agitation in a reactor with impeller, three-step flow reaction will be available: the first-step substrates were waste oil and 1/3 molar equivalent of MeOH; the second-step, the first-step eluate and 1/3 molar equivalent of MeOH; the third-step, the second-step eluate and 1/3 molar equivalent of MeOH. The conversion of waste oil to biodiesel fuel reached >90% in the two reaction systems, and the lipase catalyst could be used for >100 days without decrease of the activity. The stepwise alcoholysis could successfully be applied to ethanolysis of tuna oil. |
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