Enzymatic synthesis of short‐chain esters in n‐hexane and supercritical carbon dioxide: Effect of the acid chain length

Abstract

Enzymatic synthesis is the preferred way to produce so‐called “natural products.” Hydrolases have been used for short‐chain ester synthesis. These esters present a pleasant flavor and they have a lot of applications in different industries. Novozym 435 from Candida antarctica (EC 3.1.1.3, triacylglycerol lipase) was used for hexyl ester synthesis in n‐hexane and supercritical carbon dioxide (SCCO2). Direct esterification provided higher yields than transesterification for the synthesis of esters. Several carboxylic acids of different chain lengths were tested for the esterification reactions: acetic, propionic, butyric, caproic and caprylic acids. The reactions were carried out at 40°C and the amount of enzyme used was 13.8 g/mol alcohol. Substrates were added at equimolar concentrations, with sufficient stirring to avoid external diffusion control. Different substrate concentrations up to 1.5 M were used. The working pressure was 14 MPa in the case of SCCO2 and atmospheric pressure in the case of organic solvent. The results in both solvents show that the reaction rate increases with the chain length of the acid, but the final yields were similar. However, some of the reactions prove to be faster in SCCO2, except for hexyl acetate and propionate synthesis, in which acetic and propionic acid presented a lower solubility in SCCO2 due to its high polarity. Moreover, an acetic acid concentration of 1.5 M brought about a strong inhibition of the enzyme activity.

Ultrasound technology and molecular sieves improve the thermodynamically controlled esterification of butyric acid mediated by immobilized lipase from Rhizomucor miehei

“…Esterication reactions are usually performed in low water activity medium, and organic solvents, ionic liquids, or supercritical uids are used for this purpose. 10,26,27 In the case of organic solvents, it is convenient to use the one producing the lowest deleterious effects on enzyme activity and stability. In this work, four different organic solvents were evaluated for the esterication reactions catalyzed by Lipozyme RM-IM under ultrasound energy.…”

Effect of sub‐ and super‐critical CO2 pretreatment on conformation and catalytic properties evaluation of two commercial enzymes of CALB and Lipase PS

“…Increasing attention has been concentrated on enzymatic synthesis in supercritical carbon dioxide (SC‐CO 2 ) for biocatalytic reactions because CO 2 is nontoxic, readily available, inexpensive and easy to remove without leaving residuals in a product matrix. Enzymatic synthesis in SC‐CO 2 has been performed with respect to amidation, esterification, transesterification, carboxylation, acetylation, enantioselection, transglycosylation, reduction and hydrolysis . Many applications of SC‐CO 2 for performing enzyme catalyzed processes have revealed that it is an important sustainable, environmentally friendly and simple approach.…”

Candida rugosa lipase‐catalyzed synthesis of sucrose‐6‐acetate in a 2‐butanol/buffer two‐phase system

“…The pervious literature has reported that the regioselectivity and yields of lipase‐catalyzed reactions were dependent on the nature of the organic solvent used . Several organic solvents of low toxicity in an aqueous two‐phase system were investigated in our research.…”