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World J Microbiol Biotechnol (2015) 31:371377 DOI 10.1007/s11274-014-1789-7
ORIGINAL PAPER
Biodegradation of hexachlorobenzene by a constructed microbial consortium
Da-Zhong Yan Ling-Qi Mao Cun-Zhi Li
Jun Liu
Received: 17 February 2014 / Accepted: 19 December 2014 / Published online: 23 December 2014 Springer Science+Business Media Dordrecht 2014
Abstract A consortium comprised of an engineered Escherichia coli DH5a and a natural pentachlorophenol (PCP)
degrader, Sphingobium chlorophenolicum ATCC 39723, was assembled for degradation of hexachlorobenzene (HCB), a persistent organic pollutant. The engineered E. coli strain, harbouring a gene cassette (camA?camB?camC) that encodes the F87W/Y96F/L244A/V247L mutant of cyto-chrome P-450cam (CYP101), oxidised HCB to PCP. The resulting PCP was then further completely degraded by ATCC 39723. The results showed that almost 40 % of 4 lM HCB was degraded by the consortium at a rate of0.033 nmol/mg (dry weight)/h over 24 h, accompanied by transient accumulation and immediate consumption of the intermediate PCP, detected by gas chromatography. In contrast, in the consortium comprised of Pseudomonas putida PaW340 harbouring camA?camB?camC and ATCC 39723, PCP accumulated in PaW340 cells but could not be further degraded, which may be due to a permeability barrier of Pseudomonas PaW340 for PCP transportation. The strategy of bacterial co-culture may provide an alternative approach for the bioremediation of HCB contamination.
Keywords Biotransformation Cytochrome P-450cam
Hexachlorobenzene Pentachlorophenol Sphingobium
chlorophenolicum ATCC 39723
AbbreviationsHCB Hexachlorobenzene PCP Pentachlorophenol
Introduction
In past decades, mass production and intensive use of hexachlorobenzene (HCB) in agriculture and industrial processes has led to widespread contamination of the environment. HCB is of great concern as one of the persistent organic pollutants (POPs) named in the Stockholm Convention, due to its tendency to accumulate along the food chain and its resistance to degradation, together with its harmful effects on human beings and the environment. Although HCB production has been prohibited in most countries for many years, it is still being generated inadvertently as a by-product in several chemical processes, such as the manufacture of chlorinated solvents, chlorinated aromatics and pesticides (Jacoff et al. 1986) and is also released to the environment by incomplete combustion. HCB levels in human tissues and pine needles appear to have increased in China recently, particularly in the industrialised north-east of China (Kunisue et al. 2004; Xu et al. 2004).
Microbial biodegradation of HCB,...