Pathway and kinetics of malachite green biodegradation by Pseudomonas veronii

Jinlong Song,Yingchun Mu,Rebecca E Parales,Zhen Yang,Xu Jiang,Yani Wang,Gang Han,Miaomiao Li,Zhiyong Ruan,Dongxue Zhao,Qingyun Ma

doi:10.1038/s41598-020-61442-z

Abstract

Malachite green is a common environmental pollutant that poses a great threat to non-target organisms, including humans. This study reports the characterization of a bacterial strain, Pseudomonas veronii JW3-6, which was isolated from a malachite green enrichment culture. This strain degraded malachite green efficiently in a wide range of temperature and pH levels. Under optimal degradation conditions (32.4 °C, pH 7.1, and inoculum amount of 2.5 × 107 cfu/mL), P. veronii JW3-6 could degrade 93.5% of 50 mg/L malachite green within seven days. Five intermediate products from the degradation of malachite green were identified: leucomalachite green, 4-(dimethylamino) benzophenone, 4-dimethylaminophenol, benzaldehyde, and hydroquinone. We propose a possible degradation pathway based on these findings. The present study is the first to report the degradation of malachite green by P. veronii and the identification of hydroquinone as a metabolite in the degradation pathway.

Highlights

Malachite green is a common triphenylmethane dye that is widely used in the textile and dyeing industries
The results showed that P. veronii JW3-6 degraded most of the malachite green within the first 4 days, and its degradation efficiency exceeded 80% on day 4 (Fig. 5)
The degradation efficiencies of strain JW3-6 for ethyl violet, crystal violet, fuchsin basic, brilliant green, and victoria blue B were 91.5%, 86.4%, 75.8%, 62.2%, and 57.2% (Fig. 6). These results show that P. veronii JW3-6 has a broad specificity for the degradation of triphenylmethane dyes and has considerable potential for processing triphenylmethane dye pollution in the environment

Summary

Introduction

Malachite green is a common triphenylmethane dye that is widely used in the textile and dyeing industries. Several strains of bacteria and fungi that can decolorize or degrade triphenylmethane dyes have been isolated from soils, lakes, and liquid waste. Fungi that can degrade malachite green have been isolated; these include Cunninghamella elegans, Phanerochaete chrysosporium, and Irpex lacteus[15,16,17,18]. These microbial species serve as resources for the biodecolorization of triphenylmethane dyes and the bioremediation of environmental pollution. The objectives of the present study were: (1) to isolate a promising bacterial strain for the treatment of malachite green-contaminated environments; (2) to determine the kinetic parameters for the biodegradation of malachite green and other triphenylmethane dyes; and (3) to detect the metabolites and deduce the possible downstream degradation pathway of this strain, and examine the mechanism underlying malachite green degradation by P. veronii JW3-6

Objectives

Methods

Results

Conclusion