Feruloyl esterases immobilization in mesoporous silica particles

Mesoporous silica materials (MPS) are an interesting choice as support to immobilize enzymes because MPS offer unique properties such as high enzyme loading and tunable pore size. They also provide the enzyme with a sheltered environment therefore reducing loss of function in industrial applications. Feruloyl esterases (FAEs) are naturally hydrolytic enzymes which are known for their action on lignocellulosic material and release ferulic acid (FA) which is bound to plant cell wall materials. Under specific conditions they are also able to perform synthetic reactions. In our work we focused on performing transesterification reactions with FAEs. The synthesis of butyl ferulate (BFA) from methyl ferulate (MFA) was chosen as a model reaction. Reduced water content of the reaction system, needed for the transesterification reaction to happen, can be achieved by replacing buffer with solvents. However, solvents can have a deleterious effect on the biocatalyst. Therefore, the use of ionic liquids instead of solvents was investigated. In addition, the enzymes were immobilized on MPS. In order to achieve a good immobilization yield and a good immobilized activity of the FAEs, several parameters were varied, and enzyme activity and selectivity were assessed. Since the reaction of interest was transesterification, the selectivity of the enzyme was quantified by determining the molar ratio between the product of transesterification reaction and the product of hydrolysis reaction: BFA/FA. Kinetic parameters, stability and reusability of the immobilized biocatalyst were also investigated. We found that the properties of enzyme themselves influence the immobilization process as well as the enzyme performance. Enzymes having a different isoelectric point or bearing different surface modifications such as glycosylations have different behaviors both in terms of enzyme activity and of immobilization performance.