# Ionic Liquids for Development of Heterogeneous Catalysts Based on Nanomaterials for Biocatalysis
###### Abstract
enhanced activity and stability (10 cycles) in triacetin hydrolysis, compared with the free form and immobilized lipase on the magnetic support without IL [14]. IL moieties that were grafted to the magnetic carboxymethyl cellulose nanoparticles, were used in SILC biocatalyst synthesis. The immobilized enzymes PPL and _Penicillin_\(G\) acylase activities were tested in triacetin hydrolysis. Both the SILC biocatalysts performed higher activity and stability results than their free forms [15]. _Burkholderia cepacia_ lipase (BCL) was covalently anchored to the silica xerogel particles that were treated with protic ionic liquid (PIL), creating an SILC biocatalyst. The synthesized biocatalyst was tested for biodiesel production from different oils (soybean, colza, and sunflower), and provided a conversion between 70-98% [16]. A solid biocatalyst with ionic liquid is the immobilized enzyme on the solid matrix, which is coated with an ionic liquid layer. An example of the SCIL technique in biocatalysis is that CALB immobilized on macroporous acrylic acid beads (Novozyme 435) and coated with 1-butyl-4-methylpyridine hexafluorophosphate [4 bmpy][PF\({}_{6}\)], presented an 80% yield of methylglucose fatty acid ester synthesis [17]. Other studies presented Novozyme 435 coated with imidazolium-based ionic liquid, with [PF\({}_{6}\)]\({}^{-}\) anion, in the ring-opening polymerization (ROP) of lactones. The coated and immobilized lipase showed a two times better conversion of 8-valerolactone than uncoated Novozyme 435 [18]. The same immobilized enzyme coated with imidazolium ILs, with [NT\({}_{2}\)]\({}^{-}\) anion, was examined in poly(\(\varepsilon\)-caprolactone) synthesis. The SCIL biocatalyst provided higher enzyme activity, less IL consumption, higher molecular weight of the polymer and the synthesis yield [19]. The supported ionic liquid phase (SILP) technique consists of the physical immobilization of the enzymatic active phase on the matrix, on which the IL was adsorbed, while the supported ionic liquid-like phase (SILLP) is the method for the physical adsorption of an enzyme on the carrier, which is chemically modified with ionic liquid. The difference in the synthesis of the described carriers is in a different approach, to immobilize an IL on the matrix, for SILP in a physical way and for SILLP through covalent bonding. The applications of SILP and SILLP biocatalysts in biosynthesis, are described, in detail, later in the text. Moreover, other applications of enzymes that are immobilized on SILP and SILLP were also reported. The first example concerns the wastewater treatment. Magnetic chitosan nanoparticles, modified with amino-functionalized ionic liquid, containing 2,2-binamine-di-3-ethylbenzothiazolin-6-sulfonic acid based on copper ion chelation, were used as a carrier for lacase immobilization. The SILLP-lacase system allowed the removal of 2,4-dichlorophenol from water (50 mg/L), with 100% efficiency. SILLP provided higher activity and stability for the enzyme, compared with the free form [20]. SILLPs were also employed as great biosensors. Immobilized cytochrome C on SILLP, based on multiwalled carbon nanotubes (MWCNTs) modified glass carbon electrode, was used in the hydrogen peroxide detection. The investigated biosensor system demonstrated high selectivity, stability, and reproducibility [21]. Peroxidase (PER) from _Pisum sativum_ was immobilized on SILP, based on chitin containing gold nanoparticles and used as a biosensor in rosmarinic acid determination. The obtained biosensor presented excellent sensitivity, repeatability, reproducibility, and stability [22]. The next interesting approach is called supported ionic liquid membranes (SILMs). It was reported that enzymatic SILM could be effectively used in the separation of CO\({}_{2}\) at high temperatures. _Sulfurihydrogenbium yellowstone s carbonic anhydrase SspCA_ isozyme was immobilized on SILM made of polyvinylidene fluoride (PVDF), on which [BMIM][NT\({}_{2}\)] was adsorbed.