Biodegradation of Aromatic Compounds

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous persistent environmental contaminants generated by natural combustion processes and human activities. PAHs are considered hazardous because of cytotoxic, mutagenic, and carcinogenic effects. Sixteen individual PAH compounds have been identified as priority pollutants by the United States Environmental Protection Agency (U.S. EPA). All substances originated in to the environment by either biogenic or anthropogenic sources. Anthropogenic compounds describe synthetic compounds, and compound classes as well as elements and naturally occurring chemical entities which are mobilized by man’s activities. In the marine environment, the fate of pollutants is largely determined by biogeochem‐ ical process. Some of these chemical changes enhance the toxicity of the pollutants. Other chemical changes cause the degradation or immobilization of pollutants and, as a result, act to purify the waters. Possible fates for PAHs, released into the environment, include volatilization, photo-oxidation, chemical oxidation, bioaccu‐ mulation and adsorption on soil particles, leaching, and microbial degradation. Elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) have been found in mangrove sediments due to anthropogenic compounds. Pollution and microbial degradation have been suggested as the best way to remove PAHs from contaminated sediments. A significant positive relationship was found between bacterial growth and percentages of aromatic hydrocarbons degradation. The PAH biodegradation ability of the enriched mixed bacterial culture was not related to the degree of PAH contamination in surface sediments. The growth and biodegradation percentages of the enriched mixed culture were not higher that of the individual isolate especially at low salinity (0 and 10 ppt). The principal processes for their successful removal are currently believed to be microbial and bacteria transfor‐ © 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. mation and degradation. A large variety of bacteria are known, which can utilize PAHs as a sole source of carbon and energy under aerobic and anaerobic conditions. Biodegradation in marine environment was also described attractively. In comparison to their chemically synthesized equivalents, they have many advantages: they are environmentally friendly, biodegradable, less toxic, and nonhazardous. They have better foaming properties and higher selectivity.