Search

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]

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]

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]