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Octylphenol polyethoxylates (OPEO n) are composed of a hydrophobic octylphenol (OP) group and a hydrophilic polyethylene oxide (EO) chain and are widely used in commercial products. Shorter EO chains and OPEO n biometabolites have been identified as endocrine-disrupting contaminants and can threaten biotic factors in the ecosystem. In this study, OPEO n at three EO lengths (TX-45, TX-114, and TX-165) were selected in monomer (MN) or micelle (MC) state for batch experiments under aerobic conditions, with results showing biodegradation rates of 90 % within 35–70 h. The pseudo -first-order constant (k) of OPEO n biodegradation was observed in the order TX-45 (0.1414 h−1) > TX-114 (0.0556 h−1) > TX-165 (0.0485 h−1), with biomineralisation reaching at least 80 % for all OPEO n. The selective biodegradation of EO chains was also measured, with initial accumulation of OPEO 3 observed along with the depletion of longer EO chains for TX-45 and TX-114 in both the MN and MC states. A similar trend was observed for the MN state of TX-165, with OPEO 3 -OPEO 9 observed to accumulate and reduced after 70 h. MC biodegradation was accomplished via the initial accumulation of OPEO 3 -OPEO 9. The amounts of OPEO 3 increased and others reduced; however, OPEO 3 remained high at the end of biodegradation for TX-165. Bacterial community analysis indicated that the genera Sphingobium spp., Pseudomonas spp., Flavobacterium spp., Comamonas spp., and Sphingopyxis spp. dominate OPEO n biodegradation, and they have their roles during biodegradation, and the community-level physiological profile (CLPP) was also changed by biodegradation in both the MN and MC states. [Display omitted] • Selective biodegradation: short OPEO n accumulation and long OPEO n depletion. • OPEO n length and structures influence biodegradation. • Pseudomonas , Sphingobium and Flavobacterium spp. were dominant during degradation. • Bacterial physiological traits changed before and after biodegradation. [ABSTRACT FROM AUTHOR]

Polybrominated diphenyl ethers (PBDEs), commonly used as a flame retardants for industrial and commercial products, have a strong tendency to accumulate in the interface of water/soil/sediments and are difficult to biodegrade. An effective biological treatment for PBDE removal is needed. In this study, we investigated the use of 3 organic compost materials (BM-2, BM-6, and BP-2) to remove 20 mg kg −1 decabromodiphenyl ether (BDE-209) from contaminated sediment in anaerobic microcosms for 120 days and detected the bacterial community in samples. Organic substance of compost had sorption and biodegradation ability. BM-6 showed the highest sorption of BDE-209, at 38.95%, and BM-3 the highest biological activity, at 34.90%. Methylophilus spp., Pseudomonas spp., Clostridium spp., and Dehalococcoides sp. were identified in anaerobic microcosms with PBDE biodegradation. The pathway of anaerobic DBDE biodegradation from higher to lower brominated PBDE was identified by the appearance of PBDE biometabolites and functional genes related to reductive debromination. We have identified an effective approach for bioremediating PBDE-contaminated sediment by using organic compost; this approach is highly recommended for practical engineering for off-site remediation. [ABSTRACT FROM AUTHOR]

The effect of ORP (oxidation–reduction potential) on the bacterial community and corrosion rate was investigated in this study. A continuous sulfate-reducing bacteria (SRB)-enriched reactor equipped with an ORP controller was operated from anaerobic to anoxic condition in this bio-corrosion experiment for over 200 days. Testing mild steel coupons were placed into the reactor for immersion test which was used to compare with the result of electrochemical corrosion current density. The results showed that as the ORP increased, the sulfide, corrosion current density and the proportion of SRB in microbial community would decrease. This study employed oxygen to change the microbial communities, which successfully enabled heterotrophs to inhibit SRB even under excessive TOC and sulfate inflow conditions. However, from the results of corrosion weight loss it could be discovered that the fact of higher control of ORP leading to better corrosion inhibition was not certain. Once the ORP was controlled to −250 mV, the same result could be achieved as well as the ORP being controlled to −180 mV. In addition to the advantage of energy-saving, controlling ORP at −250 mV can also prevent more corrosion reactions from possibly being caused by other microorganisms in the continuous rising of ORP. [ABSTRACT FROM AUTHOR]

Abstract: Decabromodiphenyl ether (DBDE) is a brominated flame retardant that is commonly used in many commercial products. Sorption of DBDE within a soil/water system can result in serious bioaccumulation within the ecological system and be a threat to human health. Little is known about aerobic DBDE biodegradation, and the influence of the UV light radiation on DBDE biodegradation has not been considered. This study, for the first time, isolates DBDE biodegrading aerobic mixed bacterial cultures from DBDE-contaminated soil/water systems in Taiwan. The aerobic biodegradation of DBDE as a sole carbon source in the presence of 365 nm UVA irradiation over 10 months was investigated using a clay/water system. The rate constants for DBDE degradation gave values ranging from 0.0121 to 0.0134 day−1 in the presence of UV irradiation, which were significantly higher than the 0.0092–0.0102 day−1 values obtained in complete darkness. The aerobic metabolites: 2′,3′-dihydroxy-4-bromodiphenyl ether and 2′,3′-dihydroxy-diphenyl ether were identified by GC–MS. Debromination was ascribed to UV irradiation and biodegradation by facultative aerobic bacteria in the micro-anaerobic environment of the clay/water system. The products of debromination included 12 PBDE congeners (tri- to hexa-BDEs) and their concentrations ranged from 34.28 to 83.80 mg l−1. Specific bacteria capable of degrading PBDEs and carrying out nitrification/denitrification were identified. The present findings suggest that systems using a novel combination of photolysis and biodegradation could be developed to carry out DBDE remediation in the future. [Copyright &y& Elsevier]

Sulfate-reducing bacteria (SRB), which cause microbiologically influenced material corrosion under anoxic conditions, form one of the major groups of microorganisms responsible for the generation of hydrogen sulfide. In this study, which is aimed at reducing the presence of SRB, a novel alternative approach involving the addition of magnesium peroxide (MgO2) compounds involving the use of reagent-grade MgO2 and a commercial product (ORC™) was evaluated as a means of inhibiting SRB in laboratory batch columns. Different concentrations of MgO2 were added in the columns when black sulfide sediment had appeared in the columns. The experimental results showed that MgO2 is able to inhibit biogenic sulfide. The number of SRB, the sulfide concentration and the sulfate reducing rate (SRR) were decreased. ORC™ as an additive was able to decrease more effectively the concentration of sulfide in water and the SRB-control effect was maintained over a longer time period when ORC™ was used. The level of oxidation–reduction potential (ORP), which has a linear relationship to the sulfide/sulfate ratio, is a good indicator of SRB activity. As determined by fluorescence in-situ hybridization (FISH), most SRB growth was inhibited under increasing amounts of added MgO2. The concentration of sulfide reflected the abundance of the SRB. Utilization of organic matter greater than the theoretical SRB utilization rate indicated that facultative heterotrophs became dominant after MgO2 was added. The results of this study could supply the useful information for further study on evaluating the solution to biocorrosion problems in practical situations. [ABSTRACT FROM AUTHOR]

Microcystins (MCs) are commonly found in eutrophicated waterbodies such as lakes, ponds and reservoirs. MCs are hepatotoxins and create a high risk of liver tumors and cancer when MC-polluted water is drunk. Since MC-polluted waterbodies can form a normal part of many drinkiing water system, aggressive treatment to remove MC-LR type compounds has become an important issue worldwide. The objective of this study was to develop a method for the removal of high concentrations of MC-LRs (ppm level) by biodegradation using an indigious bacterial mixed culture isolated in Tawian. Using this culture-based biodegradation system, MC-LR removal of >99% is able to be achieved with the final concentration of MC-LR being measured to be 0.324 μg L −1 after 16 days. The pseudo -first rate constant of the MC-LR biodegradation was 876 μg L −1 day −1 during the first 4 days. The bacterial biodiversity during biodegradation was found to decrease during the first stage (Day 0–4) and then increased again during the second stage (Day 5–16), based on the Richness Index and Shannon-Wiener Diversity Index. The bacterial species identified in the mixed culture included Sphingomonas spp., Pseudoxanthomonas spp., Hyphomicrobium aestuarii , Sphingobium spp., Rhizobium spp., Steroidobacter spp. and Acinetobacter spp, all of which seem to. play important roles in MC-LR biodegradation. The genes mlrB and mlrC , which encodes proteins involved in various aspects of MC-LR biodegradation, were found to be present in the mixed cultures and are capable of being used as a biomarker for the MC-LR biodegradation process in Taiwanese reservoirs. [ABSTRACT FROM AUTHOR]

Octylphenol polyethoxylate (OPEO) surfactants are widely used as commercial cleaning products and agricultural pesticides. Sewage effluents containing high levels of OPEOs are often discharged into soil–slurry systems. OPEOs have been identified as endocrine-disrupting compounds and are a threat to organisms present in ecological systems. Several studies have previously investigated methods to degrade OPEOs; however, clarifications regarding the impact on environmental ecology and bacterial physiological changes are required. This study aimed to evaluate the changes in bacterial community and physiological characteristics that occur during OPEO biodegradation in terms of abiotic factors. The results show that adsorption of OPEO on soil can be described using the Freundlich adsorption isotherm. The rates of OPEO biodegradation in different environmental matrices were compared and the results are as follows: aqueous system > clay–slurry system > natural soil–slurry system, all of which can be identified by their distinct community-level physiological profiles (CLPPs). OPEO biodegradation is always faster in the monomer state than in the micelle state. Bacterial numbers are maintained at high level and range from 107 to 108 CFU/mL; Pseudomonas spp. is dominant and likely plays an important role in OPEO biodegradation. Fluctuations in the utilisation of carboxylic acid groups were found. The enzymatic activity of esterases was significant, ranging from 12.5–54.1%. Phosphatase activity in the soil slurries ranged from 2.1–45.8%. The responses in terms of physiological characteristics indicate the soil ecology state during OPEO biodegradation. [Display omitted] • Effective OPEO biodegradation by an indigenous mixed bacterial culture. • The influence of abiotic factors on OPEO biodegradation was evaluated. • The dominant Pseudomonas spp. plays an important role in OPEO biodegradation. • Excellent ecological indicators of carboxylic acid and esterase during degradation. [ABSTRACT FROM AUTHOR]

This research aims to analyze the variations of microbial community structure under anaerobic corrosive conditions, using molecular fingerprinting method. The effect of adding various materials to the environment on the corrosion mechanism has been discussed. In the initial experiment, sulfate-reducing bacteria (SRB) were inoculated in a series of batch culture flasks containing sterile growth media. Several testing coupons of mild steel were placed into the SRB-enriched columns, which contained excess sulfate and lactate. After incubating for 20 days, three materials (MgO 2 , H 2 O 2 and NaOCl) were added into the flasks so as to observe the effects on biocorrosion rate. Microorganism composition change was observed from the diversity profile using the PCR–DGGE (polymerase chain reaction – denaturing gradient gel electrophoresis) method. The results showed that hydrogen peroxide (H 2 O 2 ) prompted the microbial community to change quickly and easily and enhanced the corrosion rates of coupons (3–6 times faster than the control run). This fact suggested that adding H 2 O 2 could inhibit biological activities initially; however, it ultimately caused more serious corrosion due to breaking down the protective layer, composed of mainly FeS. When MgO 2 was added into the SRB-enriched culture, the corrosion rate on the mild steel test coupons was inhibited to one third of that in the control column. The DGGE profile analysis shows that SRBs were clearly inhibited for a long time (more than 100 days) after adding MgO 2 . The durability of the MgO 2 reaction could be demonstrated by DGGE variations as well as water quality monitoring results. [ABSTRACT FROM AUTHOR]