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The aim of this study is the evaluation of the enzymatic action of the ligninolytic enzyme manganese peroxidase (MnP), through a suitable addition of H(2)O(2), as a feasible system for the in vitro degradation of complex structures. For this purpose, a highly recalcitrant polymeric dye (Poly R-478) was selected as a model compound. An amperometric technique was used to determine the H(2)O(2) requirement in the decolorization by nonpurified MnP. Two H(2)O(2) supply strategies-fed-batch (every hour) or semicontinuous (every 5 min)-were applied. The addition of H(2)O(2) in pulses led to a limited decolorization after the pulses and the instantaneous consumption or decomposition of H(2)O(2). Therefore, this way of addition may limit the actual H(2)O(2) concentration in the reaction mixture. In contrast, the semicontinuous strategy maintained lower and prolonged concentrations of H(2)O(2), which allowed a clearly greater decolorization (48% after 2 h). In addition, the effect of Mn(+2) concentration on the decolorization efficiency was investigated to establish the optimal application of the MnP-oxidative system. The enzymatic treatment provoked not only the destruction of the chromophoric groups but also a noticeable breakdown of the chemical structure of the dye. In experiments with pure enzyme, MnP proved to be the main factor responsible for the dye decolorization.

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This study analyzed some alternatives to the valorization of agricultural residues considering its use in the treatment of colored effluents. The acid-base behavior of the banana peel surface was thus determined in order to establish the feasibility of its use as a bioadsorbent for dyes. The adsorption capacity of Acid Black 1 was evaluated, through the equilibrium isotherm and the kinetics of this uptake process was also analyzed. Additionally, banana peel was used as substrate-support to evaluate the growth of Inonotus sp SP2, Stereum hirsutum RU 104 and Pleurotus eryngii IJFM 169 and their ligninolytic enzymes production. The decolourization ability of strain fungi was moreover screened. The concentration of functional basic groups in the banana peel surface was determined in 5.5 mmol g -1 as six and a half times higher than acid groups, while the lowest value of the maximum adsorption capacity of Acid Black 1 was 250 mg g -1 . The adsorption kinetics of this dye was suitably represented by a pseudo second order model, obtaining correlation coefficients greater than 0.98. Additionally, the banana peel was demonstrated to be a source of carbon available for growth of the fungi studied. Reducing sugars supplied for banana peel were abruptly consumed up to the 5th day by S. hirsutum and Inonotus sp, while a slower consumption was observed in the case of P. eryngii. Manganese Peroxidase was produced by the three fungal strains, Inonotus sp. additionally produces Laccase and Aryl-alcohol oxidase.Screening assays showed that all of the dyes were decolorized, resulting in efficiencies between 50 and 99% by the three strains, with the exception of Basic Violet 4. Acid Black 1 was decolorized efficiently by Inonotus sp and S. hirsutum. In conclusion, banana peel is a promising material for development of an integral bioremediation strategy for wastewater containing hazardous compounds.

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The goal is to determinate the technical feasibility of using agroindustrial wastes for adsorption of dyes. The pHpzcof Brewer’s spent grains and Orange peel is 5.3 and 3.5, respectively. The equilibrium isotherms of Basic Blue 41, Reactiive Black 5, and Acid Black 1 were carried out without pHs control which ranging between 4 and 5.5. The equilibrium concentrations for both adsorbents were fitted by the Freundlich and Langmuir models. The maximum adsorption capacity measured for Basic Blue 41, Reactive Black 5, and Acid Black 1 was 32.4, 22.3, and 19.8 mg g-1for Brewer’s spent grains; and 157, 62.6, and 45.5 for orange peel, respectively. The kinetic of process was fitted by the model of pseudo-second order. The constant rate for orange peel decreased to extend the initial concentration of dye increased, obtaining 4.08 * 10−3−0.6 * 10−3(Basic Blue 41), 2.98 * 10−3−0.36 * 10−3(Acid Black 1), and 3.40 * 10−3−0.46 * 10−3 g mg−1 min−1(Reactive Black 5). The best removal efficiency was obtained in orange peel with values started from 63% to 20%. Consequently, according the results obtained there are two positive effects, the reuse of agricultural wastes and its use as low-cost adsorbent of the dyes.

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