Improved Enzyme Stability in Lipase-Catalyzed Synthesis of Fatty Acid Ethyl Ester from Soybean Oil |
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Authors: | Rafael Costa Rodrigues Giandra Volpato Keiko Wada Marco Antônio Záchia Ayub |
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Institution: | Department of Chemical Engineering, Federal University of Rio Grande do Sul State, Rua Professor Luiz Englert, s/n, ZC 90040-040, Porto Alegre, RS, Brazil. |
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Abstract: | In this work, we describe the optimization of the ethanolysis of soybean oil by the enzyme Lipozyme™ TL-IM in the lipase-catalyzed
biodiesel synthesis and the improvement of the enzyme stability over repeated batches. The studied process variables were:
reaction temperature, substrate molar ratio, enzyme content, and volume of added water. Fractional factorial design was used
to analyze the variables so as to select those with higher influence on the reaction and then perform a central composite
design to find the optimal reaction conditions. The optimal conditions found were: temperature, 26 °C; substrate molar ratio,
7.5:1 (ethanol/oil); enzyme content, 25% in relation to oil weight; and added water, 4% in relation to oil weight. Under these
conditions, the yield conversion obtained was 69% in 12 h. The enzyme stability assessment in repeated batches was carried
out by washing the immobilized enzyme with different solvents (n-hexane, water, ethanol, and propanol) after each batch. In the treatment with n-hexane, around 80% of the enzyme activity still remains after seven cycles of synthesis, suggesting its economical application
on biodiesel production. |
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Keywords: | Biodiesel Lipases Response surface methodology Enzyme stability Organic solvents |
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