Immobilization of feruloyl esterases Novel heterogeneous biocatalysts towards bioeconomy
Feruloyl esterases (FAES) catalyze the hydrolysis of hydroxycinnamic acids esters (HAE); the connectors between the cell wall polymers. They have also proven its efficiency during HAE synthesis, demonstrating their potential in chemical industries. Their instability at high temperatures and organic media has led to explore immobilization techniques to improve them. However, these studies are scarce and immobilization of FAES with high activity and stability is still challenging. To pave the way of FAES towards their industrial implementation, immobilization techniques must be rationally designed to achieve heterogeneous biocatalysts with high synthetic and hydrolytic activity towards lignocellulosic raw materials, useful in biorefineries. Development of these biocatalysts will contribute to the bioeconomy that must replace, or slow down, the utilization of fossil fuels.
Feruloyl esterases (FAES) are clustered as a group of a large family of hydrolases, these enzymes naturally catalyze the cleavage of ester bonds between hydroxycinnamic acids (HAs; Figure 1) and an alcohol moiety from lignocellulosic or pectinic materials (1). Nowadays, the most accepted classification of FAES is based on its homology sequence with other hydrolases and its preference to hydrolyze four methyl esters of AHs (MAHs). Thus, type A FAES have homology to some lipases and hydrolyze MAHs like sinapinate and ferulate, type B with homology with acetyl xylan esterases, and preference to hydrolyze the hydroxylated ones like caffeate and p-coumarate, and type C and D, which are unspecific and have homology to tannases and xylanases, respectively (2).
FAES are gaining importance because the HAs released from lignocelullose offer highly valuable therapeutic properties like antioxidant, antitumoral, antiviral and photoprotective (3). Additionally, FAES can also catalyze the reverse natural reaction; the synthesis of hydroxycinnamate esters starting from the HA. Those are of great interest for both food and cosmetic industries.
Several works ...