Catalytic and Physicochemical Evaluation of a TiO2/ZnO/Laccase Biocatalytic System: Application in the Decolorization of Azo and Anthraquinone Dyes

A TiO2/ZnO oxide system was proposed as a support for the immobilization of laccase from Trametes versicolor (LTV). The obtained TiO2/ZnO/LTV biocatalytic system was then applied in the decolorization/degradation of C.I. Reactive Black 5 and C.I. Acid Green 25 dyes. The efficiency of immobilization was evaluated based on catalytic properties (Bradford method, oxidation reaction of 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) and physicochemical (spectroscopic, porous, electrokinetic) analysis. The immobilization process was carried out with high performance (99.4%). Immobilized laccase retained about 40% of its activity in the whole analyzed temperature range and after 10 reaction cycles. Immobilization efficiency was also indirectly confirmed by the presence of characteristic functional groups (–C–H and –C–O), nitrogen and carbon on the TiO2/ZnO/LTV biocatalytic surface, identified by spectroscopic analyses. The increase in the surface area to 126 m2/g, change of isoelectric point (2.0) and zeta potential ranges (from +12.0 to −20.0 mV) after the immobilization process were also observed. The results show that the designed biocatalytic system enables the removal of acid dyes (C.I. Reactive Black 5 and C.I. Acid Green 25) with high efficiency (99% and 70%, respectively). Mass spectroscopy analysis indicated possible degradation products formed by the cleavage of N=N and C–N bonds.

Biodecolorization of anthraquinone dyes using immobilised mycelium of Bjerkandera adusta CCBAS930

The aim of this study was to characterize the activity of oxidoreductases during biotransformation of 0.01% anthraquinone dyes: Alizarin Blue Black B (ABBB) and Acid Blue 129 (AB129), Carminic Acid (CA), Remazol Brilliant Blue R (RBBR), Acid Green 25 (AG25) and Poly R-478 by immobilized strain of Bjerkandera adusta CCBAS 930. Phenolic compounds, phytotoxicity (Lepidium sativum L.), biotoxicity were evaluated to determine the toxicity of anthraquinone dyes before and after the treatment with immobilized B. adusta CCBAS 930. More than 60% of CA and AB129 were removed by immobilized B. adusta CCBAS after 7 days. No secondary products toxic to plants and bacteria were formed during immobilized cultures of B. adusta CCBAS 930.