Kung-Hui Chu

Biodegradation potential of wastewater micropollutants by ammonia-oxidizing bacteria

This study examined the biodegradation potential of three wastewater micropollutants (triclosan, bisphenol A, and ibuprofen) by Nitrosomonas europaea and mixed ammonia-oxidizing bacteria in nitrifying activated sludge. N. europaea could degrade triclosan and bisphenol A, but not ibuprofen. The degradation was observed only in the absence of allylthiourea (an inhibitor for ammonia monooxygenase (AMO)), suggesting that AMO might be responsible for triclosan and bisphenol A degradation. Competitive inhibition among ammonia, triclosan, and bisphenol A was observed. Inactivation of N. europaea was observed after degrading a mixture of triclosan and bisphenol A. The inactivation might be due to product toxicity and/or antimicrobial effect of triclosan; however, the causes of the inactivation were not determined. Regardless of the presence of the AMO inhibitor, three micropollutants were degraded by two different nitrified activated sludge samples. The results suggested that both ammonia-oxidizing bacteria and heterotrophic microorganisms in the activated sludge can degrade triclosan and bisphenol A. On the other hand, ibuprofen was more likely degraded by heterotrophic microorganisms in the activated sludge.

Occurrence of pharmaceuticals and personal care products along the West Prong Little Pigeon River in east Tennessee, USA.

Presence of pharmaceuticals and personal care products (PPCPs) in the environment has received a great attention due to their potential impacts on public health. This study examined the occurrence of PPCPs in West Prong Little Pigeon River in east Tennessee. As wastewater is a major source for environmental occurrence of PPCPs, both wastewater and river water samples were analyzed for nine target PPCPs and their estrogenicity. No estrogens were detected in influent, secondary effluent, and river samples. However, ibuprofen, caffeine, triclosan, bisphenol A, and bis(2-ethylhexyl)phthalate (DEHP) were detected in the influent. Ibuprofen, triclosan, and DEHP were detected in the secondary effluent samples. Only ibuprofen and triclosan were detected in river water collected near a wastewater outfall. Based on yeast estrogenic screening (YES) assays, estrogenic activities were observed in all influent, secondary effluent, and river water samples. Increased estrogenic activities were observed in river right after receiving effluent discharge, and the activities decreased as river water flowing away from the outfall. The estrogenicities of water samples measured from YES assays were much higher than those estimated from PPCP concentrations and their known estrogenicities, suggesting the presence of other unknown estrogenic compounds and/or additive effects of mixtures of estrogenic compounds at low concentrations. Results of this study demonstrated that wastewater contributed to environmental occurrence of PPCPs in the receiving water. As there is a myriad of known and unknown PPCPs in wastewater, in additional to chemical analysis, estrogenic bioassays are needed for assessing estrogenicity of environmental samples.

MTBE and Other Oxygenates: Environmental Sources, Analysis, Occurrence, and Treatment

The production and use of fuel oxygenates has increased dramatically since the early 1990s due to federal and state regulations aimed to improve air quality. Currently, methyl tert-butyl ether (MTBE) is the most widely used oxygenate in gasoline, followed by ethanol. Widespread use of oxygenates in gasoline has been accompanied by widespread release of these materials into the environment. This manuscript provides a review of environmental sources of MTBE and alternative oxygenates, analytical methods available for their detection in environmental samples, their occurrence in the environment with a focus on groundwater, and treatment methods for their removal from gasoline-contaminated water. Accidental gasoline releases from underground storage tanks and pipelines are the most significant point sources of oxygenates in groundwater. Because of their polar characteristics, oxygenates migrate through aquifers with minimal retardation, raising great concerns nationwide of their potential for reaching drinking water sources. As a group, fuel oxygenates present distinct analytical and sample preparation issues. Conventional procedures for the analysis of gasoline constituents have been shown to be insensitive for fuel oxy

Biodegradation of triclosan by a wastewater microorganism

Triclosan, a synthetic antimicrobial agent, has been considered as an emerging environmental contaminant. Here we reported a triclosan-degrading wastewater bacterial isolate, Sphingopyxis strain KCY1, capable of dechlorinating triclosan with a stoichiometric release of chloride. The stain can degrade diphenyl ether but not 2,4,4-tribromodiphenyl ether and 2,2,4,4-tetrabromodiphenyl ether, despite all these three compounds are structurally similar to triclosan. While strain KCY1 was unable to grow on triclosan and catechol, it could grow with glucose, sodium succinate, sodium acetate, and phenol. When grown with complex nutrient medium containing a trace amount of triclosan (as low as 5 μg/L), the strain could retain its degradation ability toward triclosan. The maximum-specific triclosan degradation rate (q(m)) and the half-velocity constant (K(m)) are 0.13 mg-triclosan/mg-protein/day and 2.8 mg-triclosan/L, respectively. As triclosan degradation progressed, five metabolites were identified and these metabolites continue to transform into non-chlorinated end products, which was supported by a sharp drop in androgenic potential. The activity of catechol 2,3-dioxygenase in the cell extract was detected. No triclosan degradation was observed in the presence of 3-fluorocatechol, an inhibitor of meta-cleavage enzyme, suggesting that triclosan degradation proceed via meta-cleavage pathway. Based on all the observations, a degradation pathway for triclosan by strain KCY1 was proposed.

Quantitative Molecular Assay for Fingerprinting Microbial Communities of Wastewater and Estrogen-Degrading Consortia

ABSTRACT A quantitative fingerprinting method, called the real-time terminal restriction fragment length polymorphism (real-time-t-RFLP) assay, was developed for simultaneous determination of microbial diversity and abundance within a complex community. The real-time-t-RFLP assay was developed by incorporating the quantitative feature of real-time PCR and the fingerprinting feature of t-RFLP analysis. The assay was validated by using a model microbial community containing three pure strains, an Escherichia coli strain (gram negative), a Pseudomonas fluorescens strain (gram negative), and a Bacillus thuringiensis strain (gram positive). Subsequently, the real-time-t-RFLP assay was applied to and proven to be useful for environmental samples; the richness and abundance of species in microbial communities (expressed as the number of 16S rRNA gene copies of each ribotype per milliliter) of wastewater and estrogen-degrading consortia (enriched with 17α-estradiol, 17β-estradiol, or estrone) were successfully characterized. The results of this study strongly suggested that the real-time-t-RFLP assay can be a powerful molecular tool for gaining insight into microbial communities in various engineered systems and natural habitats.

Microbial degradation of steroidal estrogens

Steroidal estrogens, widespread in the environment, are contaminants of potential concern because exposure to these compounds can cause adverse impacts on aquatic life. Intensive research efforts have been undertaken in order to better understand the environmental occurrence of these compounds. In addition to physical/chemical reactions, biological processes - microbial biodegradation of steroidal estrogens - play a vital role in determining the fate and transport of these compounds in built and natural environments. This review summarizes the current state of knowledge on the microbiology of estrogen biodegradation. Aerobic and anaerobic estrogen-degrading microorganisms are phylogenetically diverse; they are mainly isolated from soils, activated sludge, dental plaque and intestines. Estrogens can be degraded via growth-linked and non-growth-linked reactions, as well as through abiotic degradation in the presence of selective microorganisms. Current knowledge on estrogen biodegradation kinetics and pathways is limited. Molecular methods are useful in deciphering estrogen-degrading microbial community and tracking the quantity of known degraders in bioreactors with different operating conditions. Future research efforts aimed at bridging knowledge gaps on estrogen biodegradation are also proposed.

A 17β-Estradiol-utilizing Bacterium, Sphingomonas Strain KC8: Part I - Characterization and Abundance in Wastewater Treatment Plants

A 17beta-estradiol-utilizing bacterium, Sphingomonas strain KC8, was characterized in terms of its utilization kinetics toward 17beta-estradiol, estrone, and testosterone. The maximum specific substrate utilization rates (q(m)) are 0.37, 0.50, and 0.17 mg-substrate/mg-protein/day for 17beta-estradiol, estrone, and testosterone, respectively. The half-velocity constants (K(s)) are 1.9 mg/L for 17beta-estradiol, 2.7 mg/L for estrone, and 2.4 mg/L for testosterone. Strain KC8 can grow on testosterone, glucose, sodium succinate, and sodium acetate, but not on phenol. Also, strain KC8 cannot degrade two common wastewater micropollutants, bisphenol A (a plasticizer) and triclosan (an antimicrobial agent). Unlike Novosphingobium sp. ARI-1 (a known estrogen-degrader) that would lose its degradation ability toward estrone after growing on a nutrient-rich estrogen-free medium for 7 days, strain KC8 was still able to degrade both 17beta-estradiol and estrone after growing on the same medium for 15 days. Strains KC8 and ARI-1 were molecularly detected in activated sludge of municipal wastewater treatment plants (WWTPs) operating under solid retention times of 2-30 days. The concentrations of strain KC8 were 2-3 orders higher than those of strain ARI-1 in the WWTPs, suggesting that strain KC8 is ubiquitous in WWTPs and might play an important role in estrogen removal.

TCE degradation by methane-oxidizing cultures grown with various nitrogen sources

Methane-oxidizing microorganisms exhibit great potential for vadose zone bioremediation. This paper reports the effects of supplying nitrogen as nitrate, ammonia, and molecular nitrogen on the growth, trichloroethylene (TCE) degradation capacity, and energy storage capacity of a mixed methane-oxidizing culture. Cells inoculated from a nitrate-supplied methane-oxidizing culture grew fastest while fixing atmospheric nitrogen when oxygen partial pressures were kept less than 8%. Cell growth and methane oxidation were more rapid for ammonia-supplied cells than for nitrate-supplied or nitrogen-fixing cells. However, nitrogen-fixing cells were capable of oxidizing TCE as efficiently as nitrate or ammonia-supplied cells, and they exhibited the highest TCE transformation capacity of all three cultures both with and without formate as an exogenous reducing energy source. The TCE product toxicity was not as pronounced for the nitrogen fixing cells as for the nitrate- or ammonia-supplied cells after exposure to high (20 mg/L) or low (2 mg/L) TCE concentrations. Energy storage in the form of poly-{beta}- hydroxybutyrate was 20% to 30% higher for nitrogen-fixing cells; increased energy storage may be responsible for the higher transformation capacity of nitrogen-fixing cells when no external reducing energy was available. 35 refs., 4 figs., 2 tabs.

Cultivation of lipid-producing bacteria with lignocellulosic biomass: Effects of inhibitory compounds of lignocellulosic hydrolysates

Lignocellulosic biomass has been recognized as a promising feedstock for the fermentative production of biofuel. However, the pretreatment of lignocellulose generates a number of by-products, such as furfural, 5-hydroxylmethyl furfural (5-HMF), vanillin, vanillic acids and trans-p-coumaric acid (TPCA), which are known to inhibit microbial growth. This research explores the ability of Rhodococcus opacus PD630 to use lignocellulosic biomass for production of triacylglycerols (TAGs), a common lipid raw material for biodiesel production. This study reports that R. opacus PD630 can grow well in R2A broth in the presence of these model inhibitory compounds while accumulating TAGs. Furthermore, strain PD630 can use TPCA, vanillic acid, and vanillin as carbon sources, but can only use TPCA and vanillic acid for TAG accumulation. Strain PD630 can also grow rapidly on the hydrolysates of corn stover, sorghum, and grass to accumulate TAGs, suggesting that strain PD630 is well-suited for bacterial lipid production from lignocellulosic biomass.

Effects of growth substrate on triclosan biodegradation potential of oxygenase-expressing bacteria

Triclosan is an antimicrobial agent, an endocrine disrupting compound, and an emerging contaminant in the environment. This is the first study investigating triclosan biodegradation potential of four oxygenase-expressing bacteria: Rhodococcus jostii RHA1, Mycobacterium vaccae JOB5, Rhodococcus ruber ENV425, and Burkholderia xenovorans LB400. B. xenovorans LB400 and R. ruber ENV425 were unable to degrade triclosan. Propane-grown M. vaccae JOB5 can completely degrade triclosan (5 mg L(-1)). R. jostii RHA1 grown on biphenyl, propane, and LB medium with dicyclopropylketone (DCPK), an alkane monooxygenase inducer, was able to degrade the added triclosan (5 mg L(-1)) to different extents. Incomplete degradation of triclosan by RHA1 is probably due to triclosan product toxicity. The highest triclosan transformation capacity (Tc, defined as the amount of triclosan degraded/the number of cells inactivated; 5.63×10(-3) ng triclosan/16S rRNA gene copies) was observed for biphenyl-grown RHA1 and the lowest Tc (0.20×10(-3) ng-triclosan/16S rRNA gene copies) was observed for propane-grown RHA1. No triclosan degradation metabolites were detected during triclosan degradation by propane- and LB+DCPK-grown RHA1. When using biphenyl-grown RHA1 for degradation, four chlorinated metabolites (2,4-dichlorophenol, monohydroxy-triclosan, dihydroxy-triclosan, and 2-chlorohydroquinone (a new triclosan metabolite)) were detected. Based on the detected metabolites, a meta-cleavage pathway was proposed for triclosan degradation.