Imobilização de uma peroxidase de raízes de Moringa oleifera em quitosana ativada com divinil sulfona para a degradação de corantes têxteis

Abstract

The textile industry, despite its great economic importance, can cause serious risks to the environment due to the release of textile dyes, toxic compounds easily found in its effluents. Enzymatic biodegradation of textile dyes is pointed out as an efficient remediation alternative with lower environmental impact. A peroxidase purified from Moringa oleifera roots (MoPOX) is very promising for the biodegradation of textile dyes, showing efficiency of up to 65% of discoloration. MoPOX presents a purification yield of 1.97% in DEAE-Sephacel chromatography column, molecular weight of 43.6 kDa, isoelectric point of 9.4, and shows high thermostability, maintaining up to 80% of its catalytic activity even after 1h at 80 ºC. Although MoPOX displays great potential for the biodegradation of dyes, it is essential to implement immobilization methodologies so that the enzyme can be used on an industrial scale. Therefore, this work aimed to immobilize MoPOX in chitosan spheres activated with divinyl sulfone (CTS-DVS) in order to generate a stable biocatalyst for the degradation of textile dyes. MoPOX was efficiently immobilized to the support in 5 mM sodium acetate buffer pH 5.2, obtaining about 67% immobilization yield after 4 h of contact. The support showed a maximum enzyme load capacity of 300 UPA /g of support, in addition to reacting through covalent bonds with the enzyme. The characterization tests of the proposed biocatalyst demonstrated that the stabilizing property of divinyl sulfone improved the enzymatic activity in all conditions tested and rendered the immobilized enzyme more active at elevated temperatures and alkaline pHs. Thus, immobilized MoPOX showed better activity at pH 8.0 and an optimum activity temperature of 80 ° C. In addition, the immobilization process was able to maintain the thermal resistance profile presented by the soluble enzyme. The degradation of the Remazol® Blue dye occurred at pH 8.0 as a way to simulate the characteristic conditions of the textile effluent. After 6 h of reaction, immobilized MoPOX was able to degrade about 40% of the dye, while the soluble enzyme showed a degradation rate of only 8.5%. The enzymatic reuse in the dye degradation conditions demonstrated that the biocatalyst was able to maintain 36% of its initial degradation rate after seven consecutive cycles. The results obtained demonstrate the potential application of the proposed biocatalyst in the bioremediation of textile effluents.