Biodegradation of 2-chloro-4-nitrophenol via a hydroxyquinol pathway by a Gram-negative bacterium, Cupriavidus sp. strain CNP-8

Jun Min,Jinpei Wang,Xiaoke Hu,Weiwei Chen

doi:10.1186/s13568-018-0574-7

Abstract

Cupriavidus sp. strain CNP-8 isolated from a pesticide-contaminated soil was able to utilize 2-chloro-4-nitrophenol (2C4NP) as a sole source of carbon, nitrogen and energy, together with the release of nitrite and chloride ions. It could degrade 2C4NP at temperatures from 20 to 40 °C and at pH values from 5 to 10, and degrade 2C4NP as high as 1.6 mM. Kinetics assay showed that biodegradation of 2C4NP followed Haldane substrate inhibition model, with the maximum specific growth rate (μmax) of 0.148/h, half saturation constant (Ks) of 0.022 mM and substrate inhibition constant (Ki) of 0.72 mM. Strain CNP-8 was proposed to degrade 2C4NP with hydroxyquinol (1,2,4-benzenetriol, BT) as the ring-cleavage substrate. The 2C4NP catabolic pathway in strain CNP-8 is significant from those reported in other Gram-negative 2C4NP utilizers. Enzymatic assay indicated that the monooxygenase initiating 2C4NP catabolism had different substrates specificity compared with previously reported 2C4NP monooxygenations. Capillary assays showed that strain CNP-8 exhibited metabolism-dependent chemotactic response toward 2C4NP at the optimum concentration of 0.5 mM with a maximum chemotaxis index of 37.5. Furthermore, microcosm studies demonstrated that strain CNP-8, especially the pre-induced cells, could remove 2C4NP rapidly from the 2C4NP-contaminated soil. Considering its adaptability to pH and temperature fluctuations and great degradation efficiency against 2C4NP, strain CNP-8 could be a promising candidate for the bioremediation of 2C4NP-contaminated sites.

Highlights

Chloronitrophenols (CNPs) are typical representatives of chlorinated nitroaromatics, which are widely utilized in synthesizing pesticides, fungicides, drugs, dyes, among others (Arora et al 2012a, b)
The OD600 increased from initial 0.052 to final 0.135 (Fig. 1). This revealed that strain CNP-8 has the ability to utilize 2C4NP as sole source of carbon, nitrogen and energy, and the cell growth was closely correlated with the amount of 2C4NP utilized
Chemotactic assays of strain CNP‐8 We investigated the chemotactic behavior of strain CNP-8 toward variousnitrophenols by both qualitative and quantitative assays

Summary

Introduction

Chloronitrophenols (CNPs) are typical representatives of chlorinated nitroaromatics, which are widely utilized in synthesizing pesticides, fungicides, drugs, dyes, among others (Arora et al 2012a, b). Several physico-chemical methods have been reported on the degradation of 2C4NP (Priya and Madras 2006; Verma et al 2015); these methods are cost-consuming and do not yield complete mineralization of 2C4NP. RKJ800, another Gram-negative 2C4NP-utilizer, was reported to initiate 2C4NP degradation with formation of CHQ, which was dechlorinated to hydroquinone (HQ) (Arora and Jain 2012). Due to its high toxicity, 2C4NP with concentration more than 0.5 mM was reported to inhibit the growth of previously reported 2C4NP-utilizers (Arora and Jain 2012; Tiwari et al 2017). Industrial wastewaters, especially the pesticide production wastewaters, may contain high concentration of 2C4NP and the pH often varies widely. The search for new microorganisms that can adapt to a wide pH range and degrade 2C4NP at high concentration is still of great scientific and industrial significance

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Conclusion