Editorial: Special issue--Enzyme immobilization.

Immobilization of enzymes and proteins is a requirement for many industrial enzyme applications, as this facilitates enzyme recovery and reuse. Bearing in mind this necessity, the coupling of immobilization to the improvement of other enzyme features has been pursued by many researchers, and nowadays immobilization is recognized as a tool to improve not only stability, but also enzyme selectivity, specificity, resistance to inhibition or chemical modifiers, etc. To achieve these overall improvements of enzymes' properties via immobilization, it is necessary to both develop new immobilization systems suitable for these purposes, and to achieve a deeper knowledge of the mechanisms of interaction between enzymes and activated solids. That way, immobilization of enzymes, far being an old-fashioned methodology to just reuse these expensive biocatalysts, is a tool of continuous interest that requires a continuous effort to be exploited in all its potential. This special issue collects 23 papers reporting advances in the field of immobilization of enzymes. Several of the papers included on this special issue are very interesting reviews on the cutting edges of the techniques used and the future of enzyme immobilization. Thus, using oxidoreductases as a model enzyme, the possibilities of improving enzyme properties via immobilization [1] and the opportunities that inorganic materials [2] or magnetic nanoparticles provide for enzyme immobilization [3] have been reviewed. In another review, the fusion of the enzyme of interest to polyhydroxyalkanoate with covalently attached synthase is discussed as a method to achieve site-directed immobilization [4]. Reviews also include the design of enzymatic biosensors for drug screening and pharmaceutical kinetic studies [5]. Some interesting new materials for enzyme immobilization have been also proposed. For example, tailor-made siliceous ordered mesoporous materials have been used for laccase immobilization [6], methacrylate-substituted polyphosphazene beads has been used for immobilization of lipase from Candida rugosa [7], hydrophobic core-shell supports have been used to immobilize lipase B from Candida antarctica [8], inulinase has been non-covalently immobilized on carbon nanotubes [9], mixed-function-grafted mesoporous silica gel support has been used to immobilize the lipase from OPEN ACCESS