Petroleum asphaltenes: generated problematic and possible biodegradation mechanisms.

Petroleum asphaltenes are hydrocarbons that present an extremely complex molecular structure. They are conformed by different proportions of nitrogen, sulfur and oxygen. These compounds cause diverse problems like the blockage of crude oil extraction and transport pipes, the reduction of their economic use and the pollution of ecosystems. Biodegradation of asphaltenes is an important process that can eliminate these compounds and reduce the problems they cause. However, it is a process that occurs naturally in very reduced proportions. The purpose of this revision is to show the chemical structure of these compounds, the problems they cause and to represent their possible biodegradation mechanisms, based on the processes known for other hydrocarbons of complex structure. Elimination of the micelar structure, through the application of non-polar solvents, and fragmentation of the asphaltenes through photooxidation are the initial processes necessary to be able to degrade these compounds. The produced structures, such as the heteropolyaromatic and aromatic, lineal and ramified hydrocarbons, could be degraded in this order through biochemical reactions, such as omega oxidations, beta oxidations and aromatic oxidations respectively. These processes are distributed in an important variety of microorganisms. The elimination period's length can vary from one week, for the simplest structures, to 990 days for those with several condensed aromatic rings.