High efficiency production of ferulic acid by feruloyl esterase and xylanase in deep eutectic solvents

Ferulic acid is a natural phenolic chemical which widely present in plants and widely used in food and cosmetic industries. It is used as the cross-linking agent for the preparation of edible films, and as skin protection agents. Enzymatic hydrolysis of lignocellulose to produce ferulic acid has been studied for many years and is rarely used in the industry due to easy deactivation of enzymes. Deep eutectic solvent (DES) is exploited as a novel co-solvent for improving the activity and stability of enzyme. A mixed enzyme system composed of feruloyl esterase and xylanase was constructed for catalytic degradation of de-starched wheat bran (DSWB) to produce ferulic acid. When the ratio of feruloyl esterase to xylanase reached 1:1, the release of ferulic acid reached the maximum. Four DES was synthesized and evaluated the effects of compositions and concentrations on the release of ferulic acid from DSWB. The mixed enzymatic system showed the best performance in the ChCl-Gly DES aqueous solution (volume ratio of 1:2). Through the determination of the enzymatic properties and catalytic conditions, the mixed enzymatic system was applied to the catalytic reaction. Ferulic acid yield 4.2 mg/g DSWB was obtained under the optimum conditions. The results suggested that the efficient production of ferulic acid from lignocellulosic biomass can be realized through the synergistic effect of feruloyl esterase and xylanase in DES aqueous solution.