(Hydroxy)cinnamic acids (HCAs), a kind of prevalent phenolic acid compound, boast diverse biological activities. However, their limited liposolubility impedes their utilization in oil-based systems. Addressing this challenge, we presented an eco-friendly approach to synthesize (hydroxy)cinnamic monoterpenyl esters in biomass solvent 2-methyltetrahydrofuran (2-MeTHF), grafting antibacterially active monoterpenyl onto phenolic acid compounds through esterification/transesterification. This green enzymatic catalytic strategy successfully synthesized a series of cinnamic monoterpenyl esters (yield >87.84%), p -coumaric monoterpenyl esters (yield >67.26%), and caffeic monoterpenyl esters (yield >10.55%). The mechanism difference in reaction efficiency of different hydroxyl cinnamic acids was revealed through kinetic calculation and molecular docking. As the number of hydroxyl group increased, the affinity between substrates and lipase decreased, which was reflected by the K m value, in which the K m value of cinnamic acid, p -coumaric acid and caffeic acid were 23.72, 52.04 and 60.05, respectively. Furthermore, molecular docking results showed that the strong binding of the hydroxyl groups to the hydrophobic cavity of the lipase resulted in the need for more energy to twist the reaction site closer to the active center during the reaction. This research provided a green and feasible route for the synthesis of phenolic acid ester derivatives.
Dianqi Yang,Xuxu Li,Chenyu Zhang,Hong Liang,Xiaoqiang Ma
Geranyl esters (GEs) are valuable monoterpene esters derived from the esterification of geraniol and various carboxylic acids with a range of unique aromas and properties, making them valuable in perfumery, pharmaceutical, and cosmetic applications. Lipase-mediated esterification is considered to be a sustainable process but is challenged by the lack of a compatible catalytic method in conjunction with a customized microbial biosynthesis of geraniol. In this study, we developed an integrated process to convert glycerol and various carboxylates into GEs. The process includes microbial biosynthesis of geraniol using metabolically engineered Escherichia coli and enzymatic conversion of geraniol into GEs in a fermentation medium-organic biphasic system using an immobilized lipase. The enzymatic step for esterifying the target carboxylates with geraniol achieved >90% conversion under the optimized condition. Coupled with the geraniol from microbial fermentation, 0.59 g/L geranyl butyrate and 1.04 g/L geranyl hexanoate were produced subsequently, demonstrating the feasibility of converting renewable source into monoterpene esters through this integrated process, which bypassed feeding extra geraniol in the conventional lipase-mediated GE synthesis.
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