Application of an immobilized Rhizopus oryzae lipase to batch and continuous ester synthesis with a mixture of a lauric acid and fusel oil

Abstract

Five commercial lipase preparations immobilized on epoxy-polysiloxane- hydroxyethylcellulose were tested as potential biocatalysts to mediate the esterification reaction of isoamyl alcohol with lauric acid. Among them, the immobilized lipase from Rhizopus oryzae was the most active biocatalyst, attained high ester yield (81.26%) in 24 h, being selected for subsequent tests using fusel oil as a source of isoamyl alcohol under batch and continuous runs. Under batch conditions, no adverse effect was found when pure isoamyl alcohol was replaced by fusel oil. However, under continuous runs, the selected biocatalyst was found to have limited performance (half-life time = 173 h) and the average ester productivity was only 277.8 ± 19.3 μmol g−1 min−1. These results can be credited to the high affinity of the hybrid matrix for the water formed as a by-product, modifying the substrate interaction with the essential water around the enzyme limiting the substrate migration to the solid phase and thereby reducing the enzyme activity. By replacing the hybrid support for a higher hydrophobic matrix such as commercial copolymer styrene-divinylbenzene it was possible to attain a stable operation, achieving an average ester productivity of 794.43 ± 66.04 μmol g−1 min−1 and increasing the half-life time to 285 h. Further productivity incremental (1598.68 ± 135.79 μmol g−1 min−1) was also attained by using higher substrate loading. This process shows to be an attractive alternative to bulk chemical routes to satisfy increasing commercial demands for isoamyl laurate an essential emollient in the cosmetic industry.