# Ionic Liquids for Development of Heterogeneous Catalysts Based on Nanomaterials for Biocatalysis
## 3 Supported Ionic Liquid Phases in Biocatalysis
The enzyme exhibited a 118% higher catalytic activity compared to a native protein, and retained its stability, even at 80 \({}^{\circ}\)C [69]. The same SILLP magnetic matrix was applied for _Penicillin_\(G\) acylase immobilization. The synthesized carrier provided high enzyme loading and catalytic activity [70]. Another example demonstrated the use of SILLP magnetic bionanoparticles in the production of trans-free plastic fats, via enzymatic interesterifications of solid palm stearin and liquid rice bran oil in a shaking water bath. CRL, immobilized on an Fe\({}_{3}\)O\({}_{4}\)-silica hybrid modified by grafting ionic liquid particles, showed great activity, and provided the synthesis of trans-free plastic fats in the proper composition and desirable physicochemical properties. The lost activity was not reported after the separation of SILLP magnetic nanoparticles, by an external magnetic field [71]. Supported ionic liquid phases based on carbon materials, are another significant group of supports in biocatalysis. Active carbon (AC) is an interesting carbon material, with desirable properties for supports in biocatalysis. AC materials are non-toxic, cheap, commercially available, and have a large internal surface area with different sizes of pores, which enables the effective adsorption of enzymes [72]. Lipase PS from _Burkholderia ccapaia_ was immobilized on an active carbon, active carbon cloth (ACC), activated carbon paper (STV), and alumina, in the presence of ILs--[EMIM][NT\({}_{2}\)] and [EMIM][BF\({}_{4}\)]. The best results for the enzymatic kinetic resolution of 1-phenylethanol were obtained for lipase immobilized on an active carbon cloth, coated with [EMIM][NT\({}_{2}\)] in toluene. After 6 h, the achieved product's enantioselectivity was higher than 99% and the conversion reached 50%, which is the maximum for that reaction type [73]. Another worthwhile carbon material, which can be used as a support, is the carbon nanotube. Carbon nanotubes are an interesting matrix, due to their properties, which include the following: high purity (no possibility of poisoning the enzymatic active phase), mechanical and thermal stability, large surface area, and the possibility of surface functionalization [74]. CALB was immobilized via physical adsorption, on the surface of multiwalled carbon nanotubes (MWCNTs) that were modified with dialkylimidazol ionic liquids with different lengths of alkyl chains, in combination with [PF\({}_{6}\)]\({}^{-}\) anion. It was reported that the modification of MWCNTs with ILs did not destroy the support's structure. The immobilization of an enzyme on the SILLP resulted in higher activity, thermal stability, and longer reusability of the biocatalyst in triacetin hydrolysis compared with CALB adsorbed on MWCNTs, without ILs modification. The longer alkyl chain on IL's cation shows that the stabilization of the active enzyme's conformation is more efficient [75]. In the next studies, SILLPs based on MWCNTs were synthesized, as previously described, but the alkyl chain in the imidazolium ring was supplied with different functional groups, such as amino, carboxyl, and hydroxyl. Among them, the CALB-SILLP biocatalyst, functionalized with a hydroxyl group, showed the best results in the triacetin hydrolysis. A selected CALB-SILLP improved activity (18 times compared with CALB-MWCNTs) and thermal stability. Moreover, the biocatalyst retained its stability over four reaction cycles [76]. A further approach considered the selection of an appropriate ionic liquid's anion for enzyme stabilization. The synthesis pathway described above was used for CALB-SILLP production. The activity of CALB-SILLP biocatalysts with various anions ([Br]\({}^{-}\), [BF\({}_{4}\)], [PF\({}_{6}\)]\({}^{-}\) or [H\({}_{2}\)PO\({}_{4}\)]\({}^{-}\)), were examined in the triacetin hydrolysis. Five times higher activity, compared with CALB-MWCNTs, was demonstrated by CALB-SILLP with [PF\({}_{6}\)]\({}^{-}\) anion [77].