Anaerobic degradation of non-substituted aromatic hydrocarbons

2011 ◽  
Vol 22 (3) ◽  
pp. 406-414 ◽  
Author(s):  
Rainer U Meckenstock ◽  
Housna Mouttaki
Keyword(s):  
Aromatic Hydrocarbons ◽  
Anaerobic Degradation

Anaerobic digestion: concepts, limits and perspectives

2002 ◽  
Vol 45 (10) ◽  
pp. 1-8 ◽  
Author(s):  
B. Schink
Keyword(s):  
Anaerobic Digestion ◽  
Aromatic Hydrocarbons ◽  
Anaerobic Degradation ◽  
Atp Synthesis ◽  
Basic Research ◽  
Waste Materials ◽  
Natural Environments ◽  
Microbial Activities ◽  
Degradation Processes ◽  
Complex Organic

Anaerobic degradation processes are faced with limitations with respect to reaction energetics and reaction kinetics. The small amount of energy available in methanogenic degradation of complex organic compounds allows in most cases only the conservation of minimum amounts of energy in the lowest range of energy exploitable by biochemical reactions for ATP-synthesis. This limit has to be defined in the range of 1/3–1/4 of an ATP unit, or 15–20 kJ per mol reaction. Such small amounts of energy are exploited efficiently by syntrophic microbial communities co-operating e.g. in fatty acid conversion to methane and CO2. Methanogens also set the stage for efficient conversion of sugars or amino acids, and channel electron fluxes to the utmost efficiency. Kinetic limitations are set by the inertness of certain compounds, e.g. hydrocarbons, to react in the absence of a strong oxidant. New reactions have been found recently which activate such compounds, e.g. aromatic hydrocarbons such as toluene, xylenes, naphthalene, methane, or ammonia. Refined techniques for analysis of microbial activities in ill defined natural environments such as digestive tracts of small invertebrates or polluted aquifers have shown an amazing capacity for anaerobic or oxygen-limited degradation processes that are still to be exploited. Thus, anaerobic digestion is still a matter of fast increasing knowledge, both on the side of basic research as well as on the side of application in treatment of soil, waste materials, or in understanding complex living communities.

Anaerobic Degradation of Benzene and Polycyclic Aromatic Hydrocarbons

2016 ◽  
Vol 26 (1-3) ◽  
pp. 92-118 ◽  
Author(s):  
Rainer U. Meckenstock ◽  
Matthias Boll ◽  
Housna Mouttaki ◽  
Janina S. Koelschbach ◽  
Paola Cunha Tarouco ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Anaerobic Degradation ◽  
Isotope Analysis ◽  
Degradation Pathways ◽  
Batch Cultures ◽  
Polycyclic Aromatic ◽  
Pure Cultures ◽  
Biochemical Level ◽  
Microcosm Studies

Aromatic hydrocarbons such as benzene and polycyclic aromatic hydrocarbons (PAHs) are very slowly degraded without molecular oxygen. Here, we review the recent advances in the elucidation of the first known degradation pathways of these environmental hazards. Anaerobic degradation of benzene and PAHs has been successfully documented in the environment by metabolite analysis, compound-specific isotope analysis and microcosm studies. Subsequently, also enrichments and pure cultures were obtained that anaerobically degrade benzene, naphthalene or methylnaphthalene, and even phenanthrene, the largest PAH currently known to be degradable under anoxic conditions. Although such cultures grow very slowly, with doubling times of around 2 weeks, and produce only very little biomass in batch cultures, successful proteogenomic, transcriptomic and biochemical studies revealed novel degradation pathways with exciting biochemical reactions such as for example the carboxylation of naphthalene or the ATP-independent reduction of naphthoyl-coenzyme A. The elucidation of the first anaerobic degradation pathways of naphthalene and methylnaphthalene at the genetic and biochemical level now opens the door to studying the anaerobic metabolism and ecology of anaerobic PAH degraders. This will contribute to assessing the fate of one of the most important contaminant classes in anoxic sediments and aquifers.

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