[4] For example, bioreactors involve the application of both natural and additional microorganisms in controlled growth conditions that yields high biodegradation rates and can be used with a wide range of media.
[5] The rate of uptake and biodegradation by these hydrocarbon-oxidizing microbes not only depend on the chemical structure of the substrates, but is limited by biotic and abiotic factors such as temperature, salinity, and nutrient availability in the environment.
[6][7] A model microorganism studied for its role in bioremediation of oil-spill sites and hydrocarbon catabolism is the alpha-proteobacteria Alcanivorax, which degrades aliphatic alkanes through various metabolic activities.
When further supplied with sufficient limiting nutrients such as nitrogen and phosphor, it grows and produces surfactant glucolipids to help reduce surface water tension and enhance hydrocarbon uptake.
[10] The presence of crude oil along with appropriate levels of nitrogen and phosphor catalyzes the removal of petroleum either by mechanisms that enhance the efficiency of substrate uptake or by direct biodegradation of aliphatic chains.
Nutrients are injected in situ into porous media and indigenous or added microbes promote growth and/or generate products that mobilize oil into producing wells.
The two general strategies for enhancing oil recovery are altering the surface properties of the interface and using bioclogging to change the flow behavior.
The biosensor system may simply use bacterial growth as a pollutant indicator, or rely on genetic assays wherein a reporter gene is induced by the chemical.
For example, some microbes produce hydrogen sulfide as a byproduct in the degradation of certain petroleum hydrocarbons and if those gases are not detoxified before escaping the system, they can be released into the atmosphere.