The problem of environmental pollution becomes more worrisome day by day, primarily due to the large amounts of wastewater contaminated with various harmful organic compounds, discharged untreated or partially clean into the environment. Feasibility of use of horseradish peroxidase (Amoracia rusticana) in the synthetic dyes decolorization was approved by many researchers. Among a number of supports used for the immobilization, it was found that natural clay, kaolin, has excellent features which are a precondition for obtaining biocatalysts with the excellent performances. For this reason, a horseradish peroxidase was immobilized onto kaolin using glutaraldehyde as a cross-linking agent. Obtained biocatalyst was applied in the decolorization of anthraquinone dye C.I. acid violet 109. Under determined optimal conditions (pH 4.0, hydrogen peroxide concentration 0.6 mM, dye concentration 30 mg L-1 , temperature 24 °C) around 76% of dye decolorization was achieved. Reusability study showed that resulting biocatalyst was possible to apply four times in the desired reaction with relatively high decolorization percentage.

The discovery of carbon nanotubes (CNTs) has opened a new door in nanotechnology. With their high surface area, unique electronic, thermal and mechanical properties, CNTs have been widely used as carriers for protein immobilization. In fact, carbon nanotubes present ideal support system without diffusional limitations, and also have the possibility of surface covalent functionalization. It is usually the oxidation process that introduces carboxylic acid groups. Enzymes and other proteins could be adsorbed or covalently attached onto carbon nanotubes. Adsorption of enzyme is a very simple and inexpensive immobilization method and there are no chemical changes of the protein. It has also been found that this technique does not alter structure and unique properties of nanotubes. However, a major problem in process designing is relatively low stability of immobilized protein and desorption from the carrier. On the other hand, while covalent immobilization provides durable attachment the oxidation process can reduce mechanical and electronic properties of carbon nanotubes. It can also affect the active site of enzyme and cause the loss of enzyme activity. Bioimmobilization studies have showed that there are strong interactions between carbon nanotubes surface and protein. The retention of enzyme structure and activity is critical for their application and it is of fundamental interest to understand the nature of these interactions. Atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and circular dichroism (CD) spectroscopy provide an insight into the structural changes that occur during the immobilization. The aim of this paper is to summarize progress of protein immobilization onto carbon nanotubes

Finding a sustainable and ecofriendly methods for recalcitrant synthetic dyes removal is a researchers` major challenge. A carrier-free technique for commercial HRP immobilization is a focus of the present study. The immobilized biocatalyst, HRP-CLEAs with 580 U g-1 of the activity was obtained under the following immobilization conditions: precipitation reagent 80% ammonium sulphate, cross-linking reagent 1% of glutaraldehyde and protein-fedder, bovine serum albumin (BSA) concentration 5 mg ml-1. The obtained HRP-CLEAs showed great affinity towards model anthraquinone dye, C. I. Acid Violet 109. 88.4% of the dye was oxidized under the reaction conditions: pH 4, dye concentration 40 mg l-1 , H 2 O 2 concentration 1 mM and 0.1 U of HRP-CLEAs. The possibility of the immobilized biocatalyst application in five and eight oxidation cycles of the dye and pyrogallol (retained activity ~ 80%), respectively, indicates that HRP-CLEAs is an efficient and environmentally friendly biocatalyst with great potential in aromatic compounds removal from wastewater. This paper is a continuation of our earlier research related to HRP from horseradish extract immobilization in the form of CLEAs and the application in the wastewater colored with a synthetic anthraquinone dye treatment.

3-Cyano-4-(ethoxymethyl)-6-methyl-2-pyridone, an important precursor in the synthesis of vitamin B 6 , is obtained in the addition reaction between 2-cyanoacetamide and 1-ethoxy-2,4-pentanedione catalyzed by lipase from Candida rugosa (triacylglycerol acylhydrolases, EC 3.1.1.3). This work shows new experimental data and mathematical modeling of the lipase-catalyzed synthesis of 3-cyano-4-(ethoxymethyl)-6-methyl-2-pyridone. Kinetic measurements were performed at 50 °C with an enzyme concentration of 1.2 % w/v. The experimental results were fitted with two kinetic models: the ordered bi-ter and ping-pong bi-ter model, and the initial rates of the reaction were found to correlate best with the ping-pong bi-ter mechanism with inhibition by 2-cyanoacetamide. The obtained specificity constants indicated that lipase from C. rugosa had a higher affinity towards 1-ethoxy-2,4-pentanedione compared to 2-cyanoacetamide.