Anaerobic mineralization of pentachlorophenol (PCP) by combining PCP‐dechlorinating and phenol‐degrading cultures

Abstract

The dechlorination and mineralization of pentachlorophenol (PCP) was investigated by simultaneously or sequentially combining two different anaerobic microbial populations, a PCP-dechlorinating culture capable of the reductive dechlorination of PCP to phenol and phenol- degrading cultures able to mineralize phenol under sulfate- or iron-reducing conditions. In the simultaneously combined mixture, PCP (about 35 microM) was mostly dechlorinated to phenol after incubation for 17 days under sulfate-reducing conditions or for 22 days under iron-reducing conditions. Thereafter, the complete removal of phenol occurred within 40 days under both conditions. In the sequentially combined mixture, most of the phenol, the end product of PCP dechlorination, was degraded within 12 days of inoculation with the phenol degrader, without a lag phase, under both sulfate- and iron-reducing conditions. In a radioactivity experiment, [14C-U]-PCP was mineralized to 14CO2 and 14CH4 by the combined anaerobic microbial activities. Analysis of electron donor and acceptor utilization and of the production and consumption of H2, CO2, and CH4 suggested that the dechlorinating and degrading microorganisms compete with other microorganisms to perform PCP dechlorination and part of the phenol degradation in complex anoxic environments in the presence of electron donors and acceptors. The presence of a small amount of autoclaved soil slurry in the medium was possibly another advantageous factor in the successful dechlorination and mineralization of PCP by the combined mixtures. This anaerobic-anaerobic combination technology holds great promise as a cost-effective strategy for complete PCP bioremediation in situ.

Phytoremediation of pentachlorophenol-contaminated sediments by aquatic macrophytes

“…PCP is toxic to all forms of life, because it is an oxidative phosphorylation inhibitor (Yang et al 2009). Owing to its toxicity, widespread distribution and its impurities, PCP has been listed as a priority pollutant or restricted by the environmental protection agency (EPA) of USA and many other countries (e.g., dioxin, furans and hexachlorobenzene) (Cooper and Jones 2008;Dams et al 2007).…”

Anaerobic mineralization of 2,4,6-tribromophenol to CO2 by a synthetic microbial community comprising Clostridium, Dehalobacter, and Desulfatiglans

“…Additionally, the chemical concentrations used in the synthetic community in this study were much lower than those used in previous reports, i.e. 4 or 20 mM lactate, 20 mM FeO-OH, 20 mM SO 4 2- (Yang et al, 2009;Li et al, 2010Li et al, , 2013, and would avoid excessive resource consumption and decrease cost. Previous studies have reported the microbial degradation of 2,4,6-TBP aerobically or anaerobically (Ahn et al, 2003;Boyle et al, 1999;Uhnakova et al, 2009;Yamada et al, 2008).…”

“…Due to predefined characteristics, the mineralization process did not cause any secondary byproducts, which improved the management and efficiency of the system, compared to the method of inoculating undefined, mixed cultures in previously reported mineralization systems, where most of the population in the community were not involved in the mineralization process. (Yang et al, 2009;Li et al, 2010Li et al, , 2013. Restricting such unnecessary microorganisms in the reaction mixture would increase the efficiency and achieve better control of the system.…”

“…In our previous study, we demonstrated the mineralization of pentachlorophenol (PCP) by co-inoculation of multiple consortia: one reductively dechlorinating PCP and another anaerobically oxidizing the dehalogenated metabolites (less-chlorinated phenols) in a batchtype culture (Yang et al, 2009) and continuous-flow reactors (Li et al, 2010. These results indicated that functionallydesigned communities prepared by co-inoculating multiple consortia are a promising application of anaerobic systems.…”

“…However, in these combined consortia, the microbial communities were complex and included very small populations of important, functional populations such as dehalogenators and aromatic-oxidizers (Li et al, 2010. Some secondary microbial reactions occurred (Yang et al, 2009) and disturbed the mineralization process, or even rendered the system ineffective (Li et al, 2010). However, the synthetic microbial community, constructed using isolates or highly enriched microorganisms, is expected to overcome these challenges (De Roy et al, 2014).…”