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RevistaCatalysis today

Use of Lecitase-Ultra immobilized on styrene-divinylbenzene beads as catalyst of esterification reactions: effects of ultrasounds

Autores:Roberto Fernandez-Lafuente
Grupos de investigación:Optimización de biocatalizadores y bioprocesos enzimáticos
Joana S. Alves1, Cristina Garcia-Galan1,2, Daiane Danelli1, Natália Paludo1, Oveimar Barbosa3, Rafael C. Rodrigues1,*, Roberto Fernandez-Lafuente2,*
1 Biotechnology, Bioprocess and Biocatalysis Group, Institute of Food Science and Technology, Federal University of Rio Grande do Sul, Av. Bento Gonçalves, 9500, P.O. Box 15090, ZC 91501-970, Porto Alegre, RS, Brazil.
2 Department of Biocatalysis, ICP – CSIC, Campus UAM-CSIC, Cantoblanco, ZC 28049, Madrid, Spain.
3 Departamento de Química, Facultad de Ciencias, Universidad del Tolima, Ibagué, Colombia.
In this work it was evaluated for the first time, the ester synthesis catalyzed by the phospholipase Lecitase-Ultra immobilized styrene-divinylbenzene beads (MCI-Lecitase), comparing the mechanical stirring and the ultrasonic energy. It was studied the specificity of the enzyme using carboxylic acids from C4 to C18, as well as the effects of alcohol chain, organic solvents, biocatalyst content, reaction temperature and  substrate concentration. Caprylic and myristic acids were those with the highest reaction rates and yields, using ethanol as substrate. The shorter the alcohol chain, the higher the enzyme activity. Regarding the secondary alcohols, while MCI-Lecitase had no activity versus isopropanol, using 2-pentanol the activity was similar to that with 1-pentanol. Comparing the agitation systems, MCI-Lecitase presented an initial reaction rate more than 2-times higher in the ultrasound-assisted reaction than under traditional mechanical stirring. Moreover, under ultrasonic energy the maximum rate was achieved using 0.5 M of substrates, while under mechanical stirring the maximum enzyme activity was reached at 0.3 M of substrates. Concerning the operational stability, MCI-Lecitase was quite unstable, losing its activity after 6 reaction cycles. By adding molecular sieves in the reaction medium, MCI-Lecitase retained 30 % of its initial activity after 6 cycles. 
Palabras clave:Lecitase-Ultra; enzyme immobilization; styrene divinyl-benzene; esterification; ultrasound.
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