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Horseradish peroxidase (HRP) is a highly specific enzyme with great potential for use in the decolorization of synthetic dyes. A comprehensive study of HRP immobilization using various techniques such as adsorption and covalent immobilization on the novel carrier Purolite® A109 with a special focus on enzymatic decolorization and toxicity of artificially colored wastewater. The immobilized preparations with an activity of 156.21 ± 1.41 U g−1 and 85.71 ± 1.62 U g−1 after the HRP adsorption and covalent immobilization, respectively, were obtained. Stability and reusability of the immobilized preparations were also evaluated. A noteworthy decolorization level (~90%) with immobilized HRP was achieved. Phytotoxicity testing using Mung bean seeds and acute toxicity assay with Artemia salina has confirmed the applicability of the obtained immobilized preparation in industrial wastewater plants for the treatment of colored wastewater.

In this study, we assessed the effects of microwave irradiation of wheat gluten proteins as a pretreatment performed in a microwave reactor that could accurately control process parameters as a function of power and temperature, as well as comparing it with conventional heat treatment. The aim was to identify suitable combinations of partial enzymatic hydrolysis and microwave pretreatment parameters to produce gluten hydrolysates with reduced allergenicity and conserved techno-functional features for food application. FTIR analysis, and total and reactive SH group contents confirmed that the microwave-controlled heating can significantly change the secondary structure and conformation of gluten protein. The microwave treatment had the largest effect at 200 W and 100 °C, at which the content of gluten has been reduced by about 2.5-fold. The microwave pretreatment also accelerated the enzymatic hydrolysis of gluten, changing the kinetic profile. The apparent hydrolysis rate constants (k2) were 1.00, 3.68, 3.48, 4.64 and 4.17 min−1 for untreated gluten, and those pretreated with microwave power of 200, 400, 600 and 800 W, respectively. Compared to the heat treatment, it appeared that microwave specific non-thermal effects had a significant influence on the gluten structure and allergenicity and, in combination with the enzymatic hydrolysis, ultimately yielded protein hydrolysates with enhanced antioxidant and functional properties.

Gluten from wheat represents the major storage protein of the wheat grain composed of two fractions, gliadins and glutenins. Due to its availability as a by-product of the starch industry and unique viscoelastic properties, gluten plays a key role in the baking and food processing (Kong et al., 2007;Mohan Kumar et al., 2019). Both fractions are rather complex proteins generally rich in glutamine and proline, but they differ in amino acid compositions, solubility and other properties, comprising of more than 60 different polymorphic polypeptides with molecular weights ranging from 30,000 to 90,000 Da.Gliadins (prolamin fraction) are present as monomers making them soluble in aqueous alcohols like 60% ethanol. On the other hand, glutenins (glutelin fraction), are present in the form of aggregated proteins linked by interchain disulphide bonds and hydrophobic interactions, being partly soluble in diluted acids and alkalis (Scherf et al., 2016). When hydrated, gliadins contribute to the viscosity and extensibility of the dough system, whereas glutenins are responsible for dough strength and elasticity (Wieser, 2007).Since wheat represents one of the main grains in the human diet, it consequently affects the nutritional quality of the food consumed and also affects human health. Besides the quality proteins found in wheat flour, wheat grain is also a good source of essential amino acids, vitamins, minerals and fibers (Arendt & Zannini, 2013).

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