PubMed · 11770776
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R Petkewich. 2001-12-01. Deciphering PCB degradation.. https://doi.org/10.1021/es0125671
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Five bacteria were isolated from contaminated sites in Nigeria and South Africa using the culture enrichment technique. They were subjected to standard cultural, biochemical and microbiological techniques and identified to be species of Bacillus, Burkholderia, Corynebacterium, Micrococcus and Pseudomonas. Axenic cultures of the bacterial isolates utilized 1,2-dichloroethane (1,2-DCE) as the sole carbon source up to a final substrate concentration of 10 mM. Their mean generation time in 1,2-DCE ranged significantly (P<0.05) from 9.77 to 15.72 h with the maximum chloride release ranging between 59% and 86%. All the bacterial isolates produced two different dehalogenases, viz. one which is heat labile and specific for halogenated alkanes with optimum activity at a pH of 7.5 and the other which is more heat stable with a higher pH optimum of 9.0 and specific for halogenated alkanoic acids. However, the two enzyme types when tested demonstrated wide substrate specificities. It is therefore adjudged that these organisms may play a vital role in the bioremediation of sites polluted with chlorinated hydrocarbons.
We investigated the biodegradation of nonylphenol monoethoxylate (NP1EO) and nonylphenol (NP) by aerobic microbes in sediment samples collected at four sites along the Erren River in southern Taiwan. Aerobic degradation rate constants (k1) and half-lives (t1/2) for NP (2 microg g(-1)) ranged from 0.007 to 0.051 day(-1) and 13.6 to 99.0 days, respectively; for NP1EO (2 microg g(-1)) the ranges were 0.006 to 0.010 day(-1) and 69.3 to 115.5 days. Aerobic degradation rates for NP and NP1EO were enhanced by shaking and increased temperature, and delayed by the addition of Pb, Cd, Cu, Zn, phthalic acid esters (PAEs), and NaCl, as well as by reduced levels of ammonium, phosphate, and sulfate. Of the microorganism strains isolated from the sediment samples, we found that strain JC1 (identified as Pseudomonas sp.) expressed the best biodegrading ability. Also noted was the presence of 4'-amino-acetophenone, an intermediate product resulting from the aerobic degradation of NP by Pseudomonas sp.
Thermal, electric, mechanical or oxidative stress seem a promising way to reduce the production of excess activated sludge during biological wastewater treatment. However, the adaptation and the resistance of the sludge microbial ecosystem to stress conditions is a major question as it may definitively limit the effect of some treatments. Defence mechanisms developed by aerobic organisms, in particular, in response to oxidative stress involve various antioxidant activities and compounds such as glutathione. An HPLC method was developed for measuring reduced and total glutathione (GSH and GSHt) in perchloric acid sludge extracts. The method was sensitive, highly specific and validated for linearity, precision and recovery. Considering the extraction yield and the oxidation of GSH during extract storage, the measured GSH concentration was estimated to represent 60% of the GSH content from activated sludges. GSHt ranged from 0.32 to 3.34micromolg(-1) volatile solids and the GSH/GSHt ratio ranged from 32% to 91%. Measurements performed on sludges stressed in precise conditions selected to reach a reduction of sludge production showed a decrease of GSH and GSHt concentrations with thermal, mechanical, electric and ozone stress.