Heterogeneous Biocatalytic Processes of the Low-Temperature Synthesis of Esters: Selecting an Organic Solvent

• Published in: Catalysis in industry Vol. 13; no. 1; pp. 90 - 98
• Main Authors: Kovalenko, G. A., Perminova, L. V.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2021; Springer Nature B.V
• Subjects: Acetone; Adsorptivity; Aerogels; Binary mixtures; Biocatalysis; Biocatalysts; Butanol; Catalysis; Chemistry; Chemistry and Materials Science; Comparative studies; Diethyl ether; Esterification; Esters; Ethanol; Hexadecane; Hexanes; Low temperature; Octanol; Solvents; Stability; Substrates; Synthesis; Toluene; recombinant lipase; macroporous carbon aerogel; biocatalytic esterification
• ISSN: 2070-0504; 2070-0555
• DOI: 10.1134/S2070050421010074

A study is performed of the processes of low-temperature enzymatic synthesis of esters in nonaqueous media of organic solvents with the participation of heterogeneous biocatalysts produced by the adsorptive immobilization of recombinant Thermomyces lanuginosus lipase (produced by Pichia pastoris ) on macroporous carbon aerogel. Esterification is conducted in individual organic solvents of different polarities, namely nonpolar (lоg  P > 2.5) solvents hexadecane, hexane, and toluene; the polar (lоg  P < 1) diethyl ether, tert -butanol, and acetone; binary mixtures with different compositions (e.g., hexane with diethyl ether in volume ratio 1 : (1/5–3)). Comparative studies are made of the effect the nature of the solvent and co-solvent on the properties of the prepared biocatalysts (such as enzymatic activity and operational stability) in the batch esterification of heptanoic acid (C7:0) with alcohols such as polar ethanol and n ‑butanol, and nonpolar n -octanol and n -hexadecanol. The activity of the biocatalysts is found to depend largely on the polarity of both the solvents used in the reaction and the alcohol substrates. The maximum activity (400 U g −1 ; 1 U (unit of activity) = 1 μmol min −1 ) is observed in a medium of nonpolar and inviscid hexane (lоg  P = 2.9), while the minimum activity (4 U g −1 ) is detected in acetone (lоg  P  = 0.4). There is virtually no esterification of heptanoic acid in the presence of tert -butanol (lоg  P = 0.6). The activity of the biocatalysts is found to depend nonmonotonically on the lоg  P of individual solvent. In binary mixtures of such organic solvents as hexane and diethyl ether, the biocatalytic activity increases linearly as lоg  P mix increases. The biocatalysts have the maximum operational stability in binary mixture of hexane and diethyl ether.