Special Issue: Enzyme Immobilization 2016.

The use of enzymes as industrial biocatalysts is currently a solution for many problems of modern organic chemistry, which tries to carry out the most complex reactions under the rules of green chemistry [1]. In this context, enzyme immobilization is a critical point for the implementation of many processes [2]. This technique has been developed to obtain a heterogeneous biocatalyst, and thereby to produce reusable enzymes. From this necessity, immobilization has evolved to solve some other limitations of enzymes, like stability, activity, selectivity or resistance to inhibitors [3], and even to improve enzyme purity [4]. However, only properly designed immobilization strategies, based on the understanding of the protein immobilization mechanisms, may be able to optimize these results: immobilization support, active groups in the support, immobilization protocol and enzyme-support reaction end point need to be carefully selected [2–4]. From this viewpoint, immobilization of enzymes, far from being an old-fashioned methodology to just reuse these expensive biocatalysts, has become a powerful tool to greatly improve the enzyme properties [2–4]. This interest justifies the interest raised by the Special Issues in “Enzyme immobilization” published in Molecules. To the 23 papers collected in the previous issue, this new issue gathers 20 new contributions, resuming some of the most significant advances in the field of immobilization of enzymes. The reviews included in these Special Issues comprise very diverse topics. The possibilities of improving enzyme properties via immobilization, focusing on oxidoreductases, have been explained in a review paper [5] with a high impact in citations number. Other reviews have discussed the advantage of diverse materials for enzyme immobilization, like inorganic supports [6] or agarose beads [7]. Immobilization of enzymes in magnetic nanoparticles [8] has been also reviewed, showing how nanotechnology may open new opportunities to the immobilization of enzymes. In another review, the fusion of the enzymes of interest to polyhydroxyalkanoate with covalently attached synthase enzyme has been discussed as a method to achieve site-directed protein immobilization [9]. In a similar context, another review has focused on recent advances in enzyme engineering towards in situ self-assembly (bioengineering of bacteria to abundantly form enzymatically active inclusion bodies such as enzyme inclusions or enzyme-coated polyhydroxyalkanoate granules) [10]. Reviews also include the design of enzymatic biosensors for drug screening and pharmaceutical kinetic studies [11] and the immobilization of some glycoside hydrolases [12]. Some papers involve specific enzymes. For example, laccase has been immobilized in tailor-made siliceous ordered mesoporous materials [13], inulinase has been non-covalently immobilized on carbon nanotubes [14], organic/magnetic nanocarriers bearing hyperbranched poly(amido acids) were used to immobilize γ-glutamyltranspeptidase [15], wool activated by cyanuric chloride has been used to immobilize α-amylase [16], laccase has been immobilized on a pan/adsorbent composite nanofibrous membrane [17], a thermophilic esterase has been immobilized on an epoxy activated support [18], horseradish peroxidase has been attached to graphene oxide/Fe3O4 using 1-ethyl-3-(3-dimethyaminopropyl)carbodiimide as a cross-linking agent [19]. Comparison of differently