Nowadays, novel and advanced methods are being sought to efficiently remove dyes from wastewaters. These compounds, which mainly originate from the textile industry, may adversely affect the aquatic environment as well as living organisms. Thus, in presented study, the synthesized ZrO₂–SiO₂ and Cu²⁺-doped ZrO₂–SiO₂ oxide materials were used for the first time as supports for laccase immobilization, which was carried out for 1 h, at pH 5 and 25 °C. The materials were thoroughly characterized before and after laccase immobilization with respect to electrokinetic stability, parameters of the porous structure, morphology and type of surface functional groups. Additionally, the immobilization yields were defined, which reached 86% and 94% for ZrO₂–SiO₂–laccase and ZrO₂–SiO₂/Cu²⁺–laccase, respectively. Furthermore, the obtained biocatalytic systems were used for enzymatic decolorization of the Remazol Brilliant Blue R (RBBR) dye from model aqueous solutions, under various reaction conditions (time, temperature, pH). The best conditions of the decolorization process (24 h, 30 °C and pH = 4) allowed to achieve the highest decolorization efficiencies of 98% and 90% for ZrO₂–SiO₂–laccase and ZrO₂–SiO₂/Cu²⁺–laccase, respectively. Finally, it was established that the mortality of Artemia salina in solutions after enzymatic decolorization was lower by approx. 20% and 30% for ZrO₂–SiO₂–laccase and ZrO₂–SiO₂/Cu²⁺–laccase, respectively, as compared to the solution before enzymatic treatment, which indicated lower toxicity of the solution. Thus, it should be clearly stated that doping of the oxide support with copper ions positively affects enzyme stability, activity and, in consequence, the removal efficiency of the RBBR dye.

For the first time, 3D chitin scaffolds from the marine demosponge Aplysina archeri were used for adsorption and immobilization of laccase from Trametes versicolor. The resulting chitin–enzyme biocatalytic systems were applied in the removal of tetracycline. Effective enzyme immobilization was confirmed by scanning electron microscopy. Immobilization yield and kinetic parameters were investigated in detail, in addition to the activity of the enzyme after immobilization. The designed systems were further used for the removal of tetracycline under various process conditions. Optimum process conditions, enabling total removal of tetracycline from solutions at concentrations up to 1 mg/L, were found to be pH 5, temperature between 25 and 35 °C, and 1 h process duration. Due to the protective effect of the chitinous scaffolds and stabilization of the enzyme by multipoint attachment, the storage stability and thermal stability of the immobilized biomolecules were significantly improved as compared to the free enzyme. The produced biocatalytic systems also exhibited good reusability, as after 10 repeated uses they removed over 90% of tetracycline from solution. Finally, the immobilized laccase was used in a packed bed reactor for continuous removal of tetracycline, and enabled the removal of over 80% of the antibiotic after 24 h of continuous use.

Lignin-based spherical particles have recently gained popularity due to their characteristic and the usage of biopolymeric material. In this study, lignin-based spherical particles were prepared using choline chloride at different pH values, ranging from 2 to 10. Their dispersive, microstructural, and physicochemical properties were studied by a variety of techniques, including scanning electron microscopy, Fourier transform infrared spectroscopy, and zeta potential analysis. The best results were obtained for the particles prepared at pH 5 and 7, which had a spherical shape without a tendency to form aggregates and agglomerates. The lignin-based spherical particles were used for the immobilization of lipase, a model enzyme capable of catalyzing a wide range of transformations. It was shown that the highest relative activity of immobilized lipase was obtained after 24 h of immobilization at 30 °C and pH 7, using 100 mg of the support. Moreover, the immobilized lipase exhibited enhanced stability under harsh process conditions, and demonstrated high reusability, up to 87% after 10 cycles, depending on the support used. In the future, the described approach to enzyme immobilization based on lignin spheres may play a significant role in the catalytic synthesis of organic and fine chemicals, with high utility value.

The conversion of biomass components catalyzed via immobilized enzymes is a promising way of obtaining valuable compounds with high efficiency under mild conditions. However, simultaneous transformation of glucose and xylose into gluconic acid and xylonic acid, respectively, is an overlooked research area. Therefore, in this work we have undertaken a study focused on the co-immobilization of glucose dehydrogenase (GDH, EC 1.1.1.118) and xylose dehydrogenase (XDH, EC 1.1.1.175) using mesoporous Santa Barbara Amorphous silica (SBA 15) for the simultaneous production of gluconic acid and xylonic acid. The effective co-immobilization of enzymes onto the surface and into the pores of the silica support was confirmed. A GDH:XDH ratio equal to 1:5 was the most suitable for the conversion of xylose and glucose, as the reaction yield reached over 90% for both monosaccharides after 45 min of the process. Upon co-immobilization, reaction yields exceeding 80% were noticed over wide pH (7–9) and temperature (40–60 °C) ranges. Additionally, the co-immobilized GDH and XDH exhibited a significant enhancement of their thermal, chemical and storage stability. Furthermore, the co-immobilized enzymes are characterized by good reusability, as they facilitated the reaction yields by over 80%, even after 5 consecutive reaction steps.