Continuous degradation of Direct Red 23 by calcium pectate–bound Ziziphus mauritiana peroxidase: identification of metabolites and degradation routes
- 83 Downloads
In the present study, oxido-reductive degradation of diazo dye, Direct Red 23, has been carried out by Ziziphus mauritiana peroxidases (specific activity 17.6 U mg−1). Peroxidases have been immobilized via simple adsorption and cross-linking by glutaraldehyde; adsorbed and cross-linked enzyme retained 94.28% and 91.23% of original activity, respectively. The stability of peroxidases was enhanced significantly upon immobilization; a marked widening in both pH and temperature activity profiles were observed. Adsorbed peroxidases exhibited similar pH and temperature optima as reported for the free enzyme. Thermal stability was significantly enhanced in case of cross-linked enzyme which showed 80.52% activity even after 2 h of incubation at 60 °C. Packed bed reactors containing adsorbed and cross-linked peroxidases were run over a period of 4 weeks; adsorbed peroxidases retained 52.86% activity whereas cross-linked peroxidases maintained over 77% dye decolorization ability at the end of the fourth week of its continuous operation. Gas chromatography coupled with mass spectrometry was used to analyze the degradation products; it showed the presence of four major metabolites. Degradation of dye starts with the 1-Hydroxybenzotriazole radical attack on the carbon atom of the phenolic ring bearing azo linkage, converting it into cation radical which underwent nucleophilic attack by a water molecule and results in cleavage of chromophore via symmetric and asymmetric cleavage pathways. Intermediates undergo spontaneous removal of nitrogen, deamination, and oxidation reactions to produce maleic acid as the final degradation product.
KeywordsZiziphus mauritiana peroxidases Calcium pectate Cross-linking Direct Red 23 Continuous bioreactor Gas chromatography/mass spectrometry
NK thankfully acknowledges DST-PURSE programme of the government of India for providing financial assistance in the form of JRF. The author is also thankful to the USIF, AMU, Aligarh, India for SEM analysis; Department of Chemistry, AMU, Aligarh, India, is acknowledged for FTIR analysis. GC-MS analysis was performed at AIRF, JNU, New Delhi, India.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- Ali M, Ahmad M, Husain Q (2016) Redox mediated decolorization and detoxification of direct blue 80 by partially purified ginger (Zingiber officinale) peroxidase. Int J Environ Agric Res 2:19–30Google Scholar
- Bezerra CS, de Farias Lemos CMG, de Sousa M, Gonçalves LRB (2015) Enzyme immobilization onto renewable polymeric matrixes: past, present, and future trends. J Appl Polym Sci 132(26)Google Scholar
- Chatha SAS, Asgher M, Iqbal HM (2017) Enzyme-based solutions for textile processing and dye contaminant biodegradation—a review. Environ Sci Pollut Res 24(16):14005–14018Google Scholar
- Lowry OH, Rosebrough NJ, Farr AL, Randall RJ (1951) Protein measurement with the Folin phenol reagent. J Biol Chem 193(1):265–275Google Scholar
- Šekuljica NZ, Prlainović NZ, Jakovetić SM, Grbavčić SZ, Ognjanović ND, Knežević-Jugović ZD, Mijin DZ (2016) Removal of anthraquinone dye by cross-linked enzyme aggregates from fresh horseradish extract. CLEAN 44(7):891–900Google Scholar