Abstract
p-Nitrophenol (PNP) is an important environmental pollutant and can causes significant environmental and health risks. Compared with the traditional methods, biodegradation is a useful one to completely remove the harmful pollutants from the environment. Here, an engineered strain was first constructed by introducing PNP biodegradation pathway via the hydroquinone (HQ) pathway into Escherichia coli. In the engineered strain BL-PNP, PNP was completely degraded to β-ketoadipate and subsequently enter the metabolites of multiple anabolic pathways. The high tolerance and rapid degradation ability to PNP enable the engineered strain to have the potential to degrade toxic substances. The engineered strain created in this study can be used as a functional strain for bioremediation of PNP and potential toxic intermediates, and the method of assembling aromatic hydrocarbons metabolic pathway can be used to eradicate nitroaromatic pollutants in the environment.
Highlights
Nitroaromatic compounds have been widely used as dyes, pesticides, herbicides, plasticizers and explosives (Zhang et al 2018)
PnpA to pnpE for PNP degradation from Pseudomonas putida were selected for chemical synthesis, and these codons were designed and optimized according to preferential codon usage for E. coli in order to be conducive for improving gene expression (Additional file 1: Table S1)
As a commercial commodity, nitrophenols are widely used in the production of herbicides, pesticides and other aspects (Kulkarni and Chaudhari 2007), which led to serious environmental pollution
Summary
Nitroaromatic compounds have been widely used as dyes, pesticides, herbicides, plasticizers and explosives (Zhang et al 2018). The presence of these nitroaromatic compounds and their subsequent release has led to severe environmental pollution of soil, ground water and Different physical and chemical methods, including adsorption, electro or photo-catalyst have been used for removing these compounds (Vélez-Lee et al 2016). PNP would be converted to maleylacetate via hydroquinone pathway or hydroxyquinol pathway. PNP was converted to maleylacetate via four enzymes (p-nitrophenol monooxygenase, benzoquinone reductase, hydroquinone 1,2-dioxygenase, dehydrogenase) which were encoded by pnpA to pnpD, respectively. PNP was converted to 4-nitrocatechol via p-nitrophenol 2-monooxygenase, and converted to 1,2,4-benezenetriol. Maleylacetate was converted to β-ketoadipate via maleylacetate reductase, which subsequently enters metabolites in a variety of anabolic pathways, including the TAC cycle and fatty acid biosynthesis (Wells and Ragauskas 2012)
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