Biodegradation pathway for Propanii Herbicide. Genetic engineering may help degrading the recalcitrant pesticides by combining various plasmids in a bacterium. For convenience, microorganisms harbouring a variety of plasmids encoding degradation of various aromatic compounds were incubated with 2, 4, 5-T and after months microbe capable of growing on 2,4, 5-T as sole carbon source was isolated.
Sudarat Boonchan ,1 Margaret L.
Received Sep 21; Accepted Jan 4. Abstract This study investigated the biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons PAHs in liquid media and soil by bacteria Stenotrophomonas maltophilia VUN 10, and bacterial consortium VUN 10, and a fungus Penicillium janthinellum VUO 10, that were isolated from separate creosote- and manufactured-gas plant-contaminated soils.
The bacteria could use pyrene as their sole carbon and energy source in a basal salts medium BSM and mineralized significant amounts of benzo[a]pyrene cometabolically when pyrene was also present in BSM. Although small amounts of chrysene, benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene were degraded by axenic cultures of these isolates in BSM containing a single PAH, such conditions did not support significant microbial growth or PAH mineralization.
However, significant degradation of, and microbial growth on, pyrene, chrysene, benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene, each as a single PAH in BSM, occurred when P.
Polycyclic aromatic hydrocarbons PAHs occur in various ecosystems and are priority pollutants due to their potential toxicity, mutagenicity, and carcinogenicity Low-molecular-weight PAHs containing less than four benzene rings are acutely toxic, with some having effects on the reproduction and mortality rates of aquatic animals, and most high-molecular-weight PAHs containing four or more benzene rings are mutagenic and carcinogenic.
Due to their hydrophobic nature, most PAHs in aquatic and terrestrial ecosystems bind to particulates in soil and sediments, rendering them less available for biological uptake, and they also bioaccumulate in food chains Microbial degradation represents the major route responsible for the ecological recovery of PAH-contaminated sites 11 ; however, the success of bioremediation projects has been limited by the failure to remove high-molecular-weight PAHs The recalcitrance of high-molecular-weight PAHs to microbial degradation has led to research focused on evaluating a wide phylogenetic spectrum of microorganisms for their degradative ability.
This has resulted in the identification of a diverse group of bacteria and fungi that partially degrade, cometabolically oxidize, or mineralize some high-molecular-weight PAHs to detoxified products.
Reports to date indicate that the highest-molecular-weight PAHs that are mineralized as sole carbon and energy sources by bacteria contain four benzene rings, such as pyrene and chrysene. The species involved include Rhodococcus sp.
Many of these strains are also able to degrade five-benzene-ring PAHs partially, forming oxidized products.
In contrast to bacteria, fungi generally do not utilize PAHs as their sole carbon and energy source but transform these compounds cometabolically to detoxified metabolites The most extensive studies have focused on white rot fungi such as Phanerochaete chrysosporium 289Pleurotus ostreatus 341and Trametes versicolor 115 These fungi are able to degrade some five-benzene-ring PAHs and detoxify PAH-polluted soils and sediments due to the production of extracellular lignin-degrading enzymes.
Nonlignolytic fungi, such as Cunninghamella elegans, Penicillium janthinellum, and Syncephalastrum sp. However, reports on the mineralization of five-benzene-ring PAHs by pure microbial cultures are few. There is only one report that describes benzo[a]pyrene mineralization by bacteria In this case, benzo[a]pyrene was mineralized by a resting-cell suspension of S.
The failure to isolate a single microorganism capable of growing on and mineralizing PAHs with five or more benzene rings suggests that mineralization of these compounds in nature depends largely upon the cooperative metabolic activities of mixed microbial populations.
This is important for minimizing the production of toxic, water-soluble degradation by-products and reducing the risk of isolates failing to survive at contaminated sites due to the lack of suitable growth substrates.
Our previous work has focused on isolating bacterial strains from separate local PAH-contaminated sites, with an emphasis on selecting strains capable of growing on individual compounds with four or more benzene rings 622 From one of these sites, we noted that degradation of five-ring PAHs as sole carbon sources in basal salts medium BSM occurred only when a bacterial consortium grew alongside a fungal strain, and when they were separated, growth did not occur for either the fungus or the consortium.
This present study evaluated the metabolic profile of the fungal isolate and the consortium when grown alone or as a coculture. Furthermore, it reports the mineralization of benzo[a]pyrene as sole carbon and energy source for this mixed population and for a defined coculture composed of the fungus plus a single strain of S.
Fluorene was purchased from Aldrich Chemical Co. All PAHs were high-purity grade.
Bacteriological media, including nutrient agar, nutrient broth, yeast extract, and agar, were purchased from Oxoid Unipath Ltd. The composition of the BSM has been described previously MYPD broth contained 0.Biodegradation is the process by which the organic substances i.e.
the carbon based substances are broken down by the living organisms. The organic substance is transformed from. Aside from the differences between decomposition and mineralization, I want to introduce the respiration, specifically heterotrophic respiration, into the topic.
Biodegradation is the process by which the organic substances i.e. the carbon based substances are broken down by the living organisms. The organic substance is transformed from. The term biodegradation describe simple biotransformans, but the total degradation termed mineralization.
For example, an organic pollutant is minerilized if it converts to simple inorganic. Oct 01, · Biodegradation is the process of chemical breakdown of a substance to smaller products by the act of microorganisms or their enzymes. Biodegradation is often used interchangeably with “mineralization”, but, in fact, mineralization represents the breakdown of organic materials into inorganic forms brought about mainly by initiativeblog.com: Upendra THAPA SHRESTHA.
Discussion Topic: Biodegradation & Mineralization What are the differences between biodegradation and mineralization? Why are recalcitrant toxicants environmental problems?
Discussion Topic: DDT Use Describe the reasons that DDT is no longer used in the United .