Branched Metabolic Pathway for Phenanthrene Degradation in a Pyrene-Degrading Bacterium

Mycobacterium sp. strain KR2 utilizes phenanthrene and pyrene as the sole sources of carbon and energy. Its pathway for phenanthrene degradation is branched. Besides complete degradation following the Aeromonas-pathway phenanthrene is metabolized via cis-9,10-phenanthrene dihydrodiol to diphenic acid which accumulates during incubation. Both substances are not described as bacterial metabolites of phenanthrene as of yet.     

Microbial Degradation of 9,10-Phenanthrenedione

Pseudomonas sp. strain PD1 capable of utilizing 9,10-phenanthrenedione as the sole source of carbon and energy for growth was isolated from a bacterial community previously enriched from a highly PAH-contaminated soil. Diphenic acid and phthalic acid were identified as major metabolic intermediates. Phthalic acid accumulates during 9,10-phenanthrenedione degradation and possibly acts as a toxicant to the bacteria when a defined concentration is exceeded.     

Bioavailability of Heavy Metals in Soil: Impact on Microbial Biodegradation of Organic Compounds and Possible Improvement Strategies

Co-contamination of the environment with toxic chlorinated organic and heavy metal pollutants is one of the major problems facing industrialized nations today. Heavy metals may inhibit biodegradation of chlorinated organics by interacting with enzymes directly involved in biodegradation or those involved in general metabolism. Predictions of metal toxicity effects on organic pollutant biodegradation in co-contaminated soil and water environments is difficult since heavy metals may be present in a variety of chemical and physical forms. Recent advances in bioremediation of co-contaminated environments have focussed on the use of metal-resistant bacteria (cell and gene bioaugmentation), treatment amendments, clay minerals and chelating agents to reduce bioavailable heavy metal concentrations. Phytoremediation has also shown promise as an emerging alternative clean-up technology for co-contaminated environments. However, despite various investigations, in both aerobic and anaerobic systems, demonstrating that metal toxicity hampers the biodegradation of the organic component, a paucity of information exists in this area of research. Therefore, in this review, we discuss the problems associated with the degradation of chlorinated organics in co-contaminated environments, owing to metal toxicity and shed light on possible improvement strategies for effective bioremediation of sites co-contaminated with chlorinated organic compounds and heavy metals.     

降解性高分子材料的研究与开发现状

论述了光降解、生物降解和光－生物降解高分子材料的类型、性能及应用,总结了存在的问题,并提出了发展方向和建议。     

Biodegradation and detoxification of wood leachate from pentachlorophenol-treated poles

The pentachlorophenol (PCP) in leachate, generated from size-reduced PCP-treated poles, was degraded using a mixed culture containing Arthrobacter sp. in cyclic batch bioreactors in non-sterile conditions. Complete degradation of PCP was achieved for a five-month period for a concentration of 50 mg PCP/L and 12 h cycle time. The adsorbable organic halogen (AOX) concentration of the reactor effluent was reduced by two orders of magnitude compared to the feed, and the chemical oxygen demand (COD) was reduced by 50%. The increase in chloride ion concentration also suggests that PCP was mineralized to end products. In tests to increase the process throughput, complete degradation of PCP was also achieved in the cases for 120 mg PCP/L and a 12 h cycle time or 50 mg PCP/L and a 6 h cycle time. Daphnia magna toxicity tests showed that the presence of PCP in leachate caused toxicity, and the biodegradation of PCP resulted in significantly reducing the effluent toxicity to a value similar to that of PCP-free nutrient solution.