Lipase AK from Pseudomonas fluorescens and Lipase RM from Rhizomucor miehei were encapsulated into a zeolite imidazolate framework (ZIF‐8) by a “one‐pot” synthesis to obtain AK@ZIF‐8 and RM@ZIF‐8 biocatalysts. The effect of a high (1:40) and low (1:4) Zn/2‐methylimidazole molar ratio on the biocatalysts synthesis was investigated. The different Zn/ligand (L) ratios affected both the surface area, the loading, and the specific activity of the biocatalysts. Samples synthesized by using a high Zn/L ratio had high values of surface area whereas those obtained by using a low Zn/L ratio had higher loadings and specific activities. The decrease of pH (from 11.6 to 9.4) during the synthesis at high Zn/L ratio produced ZIF‐8 samples with features similar to those observed for low Zn/L ratio samples. The low Zn/L (1:4) ratio AK@ZIF‐8 biocatalyst retained 99 % activity after storage for 15 days at 5 °C and 40 % activity after five reaction cycles.

No abstract

Lipase (Pseudomonas fluorescens) and laccase (Trametates versicolor) were encapsulated on two zeolite imidazolate framework, ZIF‐8 and ZIF‐zni, materials using a one‐pot synthesis‐immobilization method in aqueous solution at room temperature. The synthesized immobilized biocatalysts (Lip@ZIF‐8, Lip@ZIF‐zni, Lac@ZIF‐8, and Lac@ZIF‐zni) were characterized by X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The enzymatic activities of the four immobilized biocatalysts were characterized via the electrochemical detection of the substrates, p‐nitrophenyl butyrate and 2,2‐azinobis‐3‐ethylbenzthiazoline‐6‐sulfonic acid. For Lip@ZIF‐8 the specific activity was 91.9 U mg−1 and 123.1 U mg−1 for Lip@ZIF‐zni, while for Lac@ZIF‐8 and Lac@ZIF‐zni, the activity was 51 U mg−1 and 163 U mg−1, respectively, confirming that laccase retains a higher level of activity when immobilized onto ZIF‐zni than on ZIF‐8. Lac@ZIF‐8 was the most stable system on storage (15 days at 5 °C), retaining 94 % of initial activity, while Lip@ZIF‐zni biocatalyst had the optimal level of reusability, retaining 40 % of initial activity after five reaction cycles.

Four different samples of ordered mesoporous silica powders (MCM-41 and SBA-15) and amino-functionalized mesoporous silica (MCM-41-NH 2 and SBA-15-NH 2 ) were used to prepare modified glassy carbon electrodes coated with ion-exchange polymer Nafion to be used for the electrochemical detection of Cd(II). The mesoporous silica samples were characterized through transmission electron microscopy, small-angle X-ray scattering, and N 2 -adsorption/desorption isotherms. The electrodes were characterized by using square wave anodic stripping voltammetry. The effect of pH and of the silica type on the electrodes’ response was investigated. The influence of amino functional groups grafted on the silica surface toward Cd(II) ion detection was also examined. The detection limits determined with the new silica-modified electrodes [between 0.36 and 1.68 μM Cd(II)] are slightly higher than those reported in the literature, but they are lower than those stipulated in the European legislation [45 μM Cd(II)] and, consequently, the electrodes could be successfully used to detect Cd(II) in aqueous solutions.

The Cover Feature illustrates the effect of two different zinc/ligand molar ratios on enzyme loading in the “one‐pot” aqueous synthesis of ZIF‐8‐encapsulated lipases from Rhizomucor miehei and Pseudomonas fluorescens. In their Full Paper, F. Pitzalis, C. Carucci et al. demonstrate that the different Zn/ligand (L) ratios affected both the surface area, the loading, and the specific activity of the biocatalysts. More information can be found in the Full Paper by F. Pitzalis, C. Carucci et al. on page 1578 in Issue 7, 2018 (DOI: 10.1002/cctc.201701984).

The Cover Feature shows lipase and laccase that were encapsulated in ZIF‐8 and ZIF‐zni metal organic framework materials using a one‐pot synthesis‐immobilization method in aqueous solution at room temperature. In their Full Paper, M. Naseri et al. demonstrate that ZIF‐zni‐immobilized laccase retains a high level of activity, whereas Lac@ZIF‐8 is the most stable system on storage (15 days at 5 °C), retaining 94 % of initial activity. Lip@ZIF‐zni biocatalyst has an optimal level of reusability. More information can be found in the Full Paper by M. Naseri et al. on page 5425 in Issue 23, 2018 (DOI: 10.1002/cctc.201801293).