期刊
CHEMOSPHERE
卷 291, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2021.132934
关键词
NahAa enzyme; Naphthalene degradation; Combined pollution; Enzyme immobilization; Functionalized MWCNTs; Cr(VI) wastewater treatment
资金
- Fundamental Research Funds for the Central Universities grant [lzujbky-2017-br01]
- Gansu province major science and technology projects [17ZD2WA017]
- National Natural Science Foundation [31870082]
This study showed that the naphthalene degradation enzyme NahAa from P. brassicacearum LZ-4 can reduce Cr(VI). The enzyme was immobilized on multi walled carbon nanotubes to form a stable and efficient composite MWCNT-NahAa, which exhibited a higher Cr(VI) reduction efficiency in wastewater treatment.
Pseudomonas brassicacearum LZ-4 is a facultative anaerobic bacterium, can efficiently degrade naphthalene and reduce chromate simultaneously. In this study, we showed that the naphthalene degradation enzyme NahAa from P. brassicacearum LZ-4 can reduce Cr(VI). Heterologous expression in E. coli S17-1 along with RNA interference of NahAa in strain LZ-4 showed the enzyme can reduce chromate in vivo. In vitro, purified NahAa was identified and can catalyze Cr(VI) reduction by 64.2%. Flavin adenine dinucleotide (FAD) was identified as a cofactor of NahAa, which Cr(VI) could obtain electrons from NADH through NahAa-associated FAD for reduction. Immobilized NahAa on functional multi walled carbon nanotubes via physical adsorption method to produce a stable, high efficient composite MWCNT-NahAa. The maximum efficiency of MWCNT-NahAa composite was obtained in enzyme concentrations of 6 mg/mL and 20 min immobilization time. The optical reaction conditions for MWCNT-NahAa were pH 7.0 and 30 degrees C, still retaining 50% of its initial activities after five consecutive cycles. Application of composites in wastewater can reduce 90.4% Cr(VI), higher than free NahAa that was 63.5%. To our best knowledge, this is the first report immobilized enzyme in polycyclic aromatic hydrocarbons-degradation pathway for Cr(VI) wastewater treatment, providing a new insights on combined pollution remediation.
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