Microbial degradation bioremediation

Juhasz AL, R Naidu (2000) Bioremediation of high molecular weight polycyclic aromatic hydrocarbons a review of the microbial degradation of benzo[a]pyrene. Int Biodet Biodeg 45 57-88. 

Bioremediation is a technique for treating zones of contamination by microbial degradation, which involves altering the environmental conditions to enhance microbial catabolism or cometabolism of organic contaminants, resulting in the breakdown and detoxification of those contaminants.15 According to microbial metabolic activity, bioremediation can be classified into three categories20-21 ... 

Atlas, R. M. (1991). Microbial hydrocarbons degradation-bioremediation of soil spills. Journal of Chemical Technology and Biotechnology, 52, 149—56. 

As versatile as bioremediation may seem, there are certain complex xenobiotic chemicals which have proven resistant to microbial degradation. Nevertheless, the state-of-the-art in bioremediation of inorganic and recalcitrant organic contaminants is rapidly advancing. 

Available data suggest that the supra-CMC inhibitory effect on biodegradation is reversible and not a specific toxic effect. Partial inhibition of microbial degradation of phenanthrene was observed for nonionic surfactants at sub-CMC doses. It is not clear whether these effects result from surfactant interactions with microorganisms or from preferential use of surfactant as substrate or source of carbon. The effects of surfactant monomers and micelles on microbial cell surfaces and constituents, and effects related to preferential substrate utilization and mineralization of degradation products, must be better understood in order to evaluate whether synthetic surfactants may be employed advantageously to enhance bioremediation in soil-water systems. 

As part of its operations between 1955 and 1977, a Finnish sawmill had been impregnating timber with a preservative to inhibit microbial degradation. This product, called Ky-5, contained a mixture of chlorophenols, namely, 2,4,6-trichlorophenol (7-15%), 2,3,4,6-tetrachlorophenol ( 80%) and pentachlorophenol (6-10%). Ky-5 also contained traces of polychlorinated phenoxyphenols and dibenzo-p-dioxins as impurities. Over the years this product had contaminated the soils around the sawmill. A cost-effective bioremediation strategy was needed that could be used at this site but also throughout Finland where 800 other sites of this type existed. 

More recent laboratory studies from Niqui-Arroyo et al. (2006) and Niqui-Arroyo and Ortega-Calvo (2007) demonstrated an up to 10-fold increase of PAH degradation in experiments with applied electric field compared with control experiments without electric current. Additionally, they showed that a periodic change of electrode polarity resulted in a more stable and better degradation efficiency. Also Luo et al. (2005) observed a stimulated microbial degradation of phenol in the presence of an electric field. In their experiments, bioremediation rates could be increased... 

Anderson TA, Walton BT. Comparative plant uptake and microbial degradation of trichloroethylene in the rhizospheres of five plant species Implications for bioremediation of contaminated surface soUs. ORNL/TM-12017. Oak Ridge, TN. 1992 pp.l86. 

Enrichment culture techniques can also be used for bioremediation to detoxify xenobiotic pollutants such as polycyclic aromatic hydrocarbons (PAHs), heterocyclic polyaromatics, and halogenated aromatics in soils and sediments through microbial degradation. An effective way to do this is by isolating microbes through enrichment cultures with the substrate one wants to detoxify as a limiting compound. Once this is proven in the laboratory, it can be taken full-scale to the field. 

Atlas RM (1991) Microbial hydrocarbon degradation-bioremediation of oil spills. J Chem Technol Biotechnol 52 149-156... 

This article will present a critical overview of the major known catabolic mechanisms and will discuss several new insights in microbial degradation of nitro-substituted aromatic compounds. These data will be weighed with respect to their applicability for bioremediation of contaminated soil. Based on the current status of knowledge, two alternative processes will be discussed in more detail. 

If there are significant amounts of both volatile and nonvolatile contaminants, remediation may be achieved by a combination of Hquid and vapor extraction of the former, and bioremediation of the latter. This combination has been termed "bioslurping", where the act of pumping out the Hquid contaminant phase draws in air at other wells to stimulate aerobic degradation (20). Such bioremediation requites that there be enough nutrients to allow microbial growth, and fertilizer nutrients are frequendy added at the air injection wells. Bioslurping has had a number of weU-documented successes. 

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