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  • Laccase immobilized on chit...
    Ruxandra Leontieș, Anca; Răducan, Adina; Cristina Culiță, Daniela; Alexandrescu, Elvira; Moroșan, Alina; Eduard Mihaiescu, Dan; Aricov, Ludmila

    Chemical engineering journal (Lausanne, Switzerland : 1996), 07/2022, Letnik: 439
    Journal Article

    •Chitosan and polyacrylic acid microspheres were designed as carriers for laccase.•A multi-step laccase immobilization procedure with zero length crosslinker was used.•The polyacrylic acid content modulated the support and immobilized enzyme properties.•The immobilized product efficiently discolored naphthol green B and indigo carmine.•The immobilization improved the kinetic profile of laccase in dyes decomposition. Low cost and non-toxic microspheres constituted by different ratios of chitosan (Cs) and polyacrylic acid (PAA) were manufactured as carriers for laccase (Lc). The CsPAA microspheres characterization proved that the PAA content played an important role on the size, surface morphology and rheological properties, and modulated the enzyme immobilization. The immobilization of Lc involved a multi-step procedure in which the 1-ethyl-3-(3-dimethylaminopropyl carbodiimide hydrochloride (EDC) was used as “zero length” crosslinker. The product with the largest active enzyme amount (44.38 mg Lc/g dry support), and the best operational stability profile was 10CsPAALc3. Also, this product contained the lowest PAA concentration and had excellent rheological properties. Moreover, two current hazardous chemicals, indigo carmine (IC) and naphthol green B (NG), were used as model dyes in practical applications. The biocatalytic decomposition of NG and IC was 1.67 and 2.4 times faster for 10CsPAALc3 compared to the free enzyme. The kinetic profile revealed that the immobilized Lc was less prone to substrate, operational and thermal inactivation. For example, the thermal inactivation for 10CsPAALc3 decreased by approximately 25% when dyes were used as substrate and by 11.71% for ABTS, as compared with the free Lc. The recycling test showed that in 5 cycles the immobilized Lc preserves 81% with NG and respectively 72% for IC of initial activity. The results prove that the new immobilized product can be successfully used in indigoid and metal-complex dyes biodegradation.