Improved enzyme stability in lipase-catalyzed synthesis of fatty acid ethyl ester from soybean oil.
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 degrees 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.
Costa Rodrigues
Rafael
R
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.
Volpato
Giandra
G
Wada
Keiko
K
Záchia Ayub
Marco Antônio
MA
D000704:Analysis of Variance; D055162:Biocatalysis; D004795:Enzyme Stability; D004952:Esters / Q000378:metabolism*; D000431:Ethanol; D005227:Fatty Acids / Q000096:biosynthesis*; D008049:Lipase / Q000378:metabolism*; D008954:Models, Biological; D015203:Reproducibility of Results; D013024:Soybean Oil / Q000378:metabolism*; D013997:Time Factors
D004952:Esters; D005227:Fatty Acids; D000431:Ethanol; D013024:Soybean Oil; D008049:Lipase