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Lipase in biphasic alginate beads as a biocatalyst for esterification of butyric acid and butanol in aqueous media

Ng, Choong Hey, Yang, Kun-Lin
Enzyme and Microbial Technology 2016 v.82 pp. 173-179
Clostridium, biocatalysts, butanol, butyric acid, calcium alginate, carboxylic ester hydrolases, culture media, esterification, fermentation, hexadecane, iso-octanes, solvents, thermodynamics, toxicity
Esterification of organic acids and alcohols in aqueous media is very inefficient due to thermodynamic constraints. However, fermentation processes used to produce organic acids and alcohols are often conducted in aqueous media. To produce esters in aqueous media, biphasic alginate beads with immobilized lipase are developed for in situ esterification of butanol and butyric acid. The biphasic beads contain a solid matrix of calcium alginate and hexadecane together with 5mg/mL of lipase as the biocatalyst. Hexadecane in the biphasic beads serves as an organic phase to facilitate the esterification reaction. Under optimized conditions, the beads are able to catalyze the production of 0.16mmol of butyl butyrate from 0.5mmol of butyric acid and 1.5mmol of butanol. In contrast, when monophasic beads (without hexadecane) are used, only trace amount of butyl butyrate is produced. One main application of biphasic beads is in simultaneous fermentation and esterification (SFE) because the organic phase inside the beads is very stable and does not leach out into the culture medium. SFE is successfully conducted with an esterification yield of 6.32% using biphasic beads containing iso-octane even though the solvent is proven toxic to the butanol-producing Clostridium spp.