NahAa can convert naphthalene and reduce chromate simultaneously and immobilized on functional multiwall carbon nanotubes for 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 °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. © 2021 Elsevier Ltd

Zhao S.1 , Feng P.1 , Yu Z.1 , Zhou T.1 , Gao T.2 , Redina M.M. 3 , Liu P. 1 , Li X. 1
Elsevier Ltd
  • 1 Gansu Key Laboratory of Biomonitoring and Bioremediation for Environment Pollution, School of Life Sciences, Lanzhou University, 222 South Tianshui Rd, Lanzhou, Gansu 730000, China
  • 2 School of Biological and Environmental Engineering, Xi'an University, Xi'an, 710065, China
  • 3 Peoples' Friendship University of Russia, Miklukho-Maklaya Str., 6, Moscow, 117198, Russian Federation
Ключевые слова
Combined pollution; Cr(VI) wastewater treatment; Enzyme immobilization; Functionalized MWCNTs; NahAa enzyme; Naphthalene degradation
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