Edgardo Martín Contreras

In recent years, the peroxidase enzymes have generated wide interest in several industrial processes, such as wastewater treatments, food processing, pharmaceuticals, and the production of fine chemicals. However, the low stability of the peroxidases in the presence of hydrogen peroxide (H₂O₂) has limited its commercial use. In the present work, the effect of H₂O₂ on the inactivation of horseradish peroxidase (HRP) was evaluated. Three states of HRP (E₀, E₂, and E₃) were identified. While in the absence of H₂O₂, the resting state E₀ was observed, in the presence of low and high concentrations of H₂O₂, E_2, and E₃ were found, respectively. The results showed that HRP catalyzed the H₂O₂ decomposition, forming the species E_x, which was catalytically inactive. Results suggest that this loss of enzymatic activity is an intrinsic characteristic of the studied HRP. A model from a modified version of the Dunford mechanism of peroxidases was developed, which was validated against experimental data and findings reported by the literature.

En el presente estudio se acondicionó un biomaterial a base de pulpa de papa liofilizada (PPL) para la remoción de un colorante industrial, Orange II (S), con peróxido de hidrógeno (P). El uso de enzimas es actualmente una de las tecnologías más promisorias para la eliminación de contaminantes industriales recalcitrantes. Se caracteriza la actividad peroxidasa de PPL mediante la oxidación de ácido 2,2'-azino-bis-(3-etillbenzotiazolin-6-sulfónico) (ABTS) y su capacidad para remover S. Los resultados indicaron que PPL es una potencial fuente de enzima peroxidasa y que además tiene la capacidad para eliminar el Orange II mediante oxidación enzimática y bioadsorción. Esto aporta la catálisis enzimática, un 65 % de la remoción total del colorante. Se concluye que la decoloración de S con P en presencia de PPL es conveniente realizarla a pH 9 y un valor inicial de P₀/S₀ = 10 mol/mol.

The use of mixed microbial cultures (MMC) and organic wastes and wastewaters as feed sources is considered an appealing approach to reduce the current polyhydroxyalkanoates (PHAs) production costs. However, this method entails an additional hurdle to the PHAs downstream processing (recovery and purification). In the current work, the effect of a sodium hypochlorite (NaClO) pre-treatment coupled with dimethyl carbonate (DMC) or chloroform (CF) as extraction solvents on the PHAs recovery efficiency (RE) from MMC was evaluated. MMC were harvested from a sequencing batch reactor (SBR) fed with a synthetic prefermented olive mill wastewaster. Two different carbon-sources (acetic acid and acetic/propionic acids) were employed during the batch accumulation of polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from MMC. Obtained PHAs were characterized by ¹H and ¹³C nuclear magnetic resonance, gel-permeation chromatography, differential scanning calorimetry, and thermal gravimetric analysis. The results showed that when a NaClO pre-treatment is not added, the use of DMC allows to obtain higher RE of both biopolymers (PHB and PHBV), in comparison with CF. In contrast, the use of CF as extraction solvent required a pre-treatment step to improve the PHB and PHBV recovery. In all cases, RE values were higher for PHBV than for PHB.

Fish processing generates plenty of waste that is directly discarded in open‐air dumps and water sources, or treated in the same way as urban solid waste, causing serious pollution problems. The waste represents a significant source of high‐value bioproducts with potential applications in different industrial processes such as the production of feed, fertilizers, biodiesel and biogas, detergent additives and cosmetics. The objective of this study was to characterize and compare specific activities under different pH values and temperature conditions of acid and alkaline proteinases and viscera yield from the following fish species: Argentine hake Merluccius hubbsi, Brazilian flathead Percophis brasiliensis, Brazilian codling Urophycis brasiliensis and Stripped weakfish Cynoscion guatucupa. Individuals were fished off the coast of Mar del Plata (Argentina) by a commercial fleet and the viscera were immediately extracted and kept on ice until use. Stomach proteinases from four species had the highest activity at pH 2, with stability in the range of pH 2–4. The optimum pH was 11.5 from intestinal enzymes of C. guatucupa, M. hubbsi and P. brasiliensis and 9.5 from intestinal enzymes of U. brasiliensis. Alkaline proteinases from all species were highly stable in the range of 7–11.5. The optimum temperature of stomach proteinases from the four species studied were 30 and 50°C, with stability at 10 and 30°C during 150 min. The optimum temperature of intestinal enzymes from the tested species were 50°C with high stability at 10 and 30°C during 150 min. Alkaline proteinase from all species and acid proteinases from C. guatucupa were inactive at 70°C after 150 min, while there was a residual activity lower than 5% at 80°C on pre‐incubated stomach enzymes of M.hubbsi, P. brasiliensis and U. brasiliensis after 5, 10 and 20 min, respectively. Digestive proteinases recovered in this study could be appropriate for technological usage, reducing manufacturing costs, obtaining revenue from fishery wastes, and contributing to the reduction of environmental pollution.