Heterogeneous biocatalytical esterification by recombinant Thermomyces lanuginosus lipase immobilized on macroporous carbon aerogel

Abstract

Heterogeneous biocatalysts prepared by immobilizing recombinant lipases are promising for implementation in organic synthesis of various esters used as fragrances, emollients, emulsifiers, non-ionic surfactants, plasticizers, etc. For this research, the Thermomyces lanuginosus lipase produced by the authoring recombinant Pichia pastoris strain was adsorbed on the authoring macroporous carbon aerogel. The prepared biocatalysts were studied in the periodic processes of enzymatic esterification carried out in nonconventional anhydrous media of organic solvents at ambient conditions (22 ± 2 °C, 1 bar). Biocatalytical activities depended strongly on both the selected pair of lipase substrates (acid and alcohol) involved in reaction and the organic solvent used for esterification. The reaction rates of fatty C7 acid esterification with double and triple bond C3 alcohols, such as allyl and propargyl alcohols, were found to be 2–4 times lower than with aliphatic propanol. Isomerism of an acid (not alcohol) molecule greatly affected the esterification rates. It was observed that isomers of C4 and C5 acids (iso-butyric and iso-valeric) practically did not react with butanol. The esterification rates strongly depended on the polarity of the organic solvent characterized by the parameter logP. With an increase in the solvent polarity from non-polar hexane to polar acetone, the esterification rate decreased by two orders of magnitude. The prepared lipase-active biocatalysts had a sufficiently high operational stability under the chosen optimal reaction conditions; their stationary activity (300 ± 100 U·g–1) did not change in periodic reaction cycles during several tens of hours.