Methane methanotrophs

In some cases, microorganisms can transform a contaminant, but they are not able to use this compound as a source of energy or carbon. This biotransformation is often called co-metabolism. In co-metabolism, the transformation of the compound is an incidental reaction catalyzed by enzymes, which are involved in the normal microbial metabolism.33 A well-known example of co-metabolism is the degradation of (TCE) by methanotrophic bacteria, a group of bacteria that use methane as their source of carbon and energy. When metabolizing methane, methanotrophs produce the enzyme methane monooxygenase, which catalyzes the oxidation of TCE and other chlorinated aliphatics under aerobic conditions.34 In addition to methane, toluene and phenol have been used as primary substrates to stimulate the aerobic co-metabolism of chlorinated solvents. 

Methane Methanotrophic Methane hydroxylation EX29EX2HX64EX33EX2H Hydroxo, aqua... 

Strong evidence that the methanotrophic bacteria use the Wood-Ljungdahl pathway in reverse for the conversion of acetate to methane. ... 

The acetyl-coenzyme A decarbonylase synthase complex contains five polypeptide sub-nnits and in acetate-degrading methanotrophs, such as Methanosarcina barkeri and M. thermophila, catalyzes the formation of methane and COj from acetyl-CoA ... 

Methane monooxygenase may exist in either soluble (sMMO) or particulate (pMMO) forms. These display different substrate ranges and different rates of transformation rates, and most methanotrophs express only the latter form of the enzyme (Hanson and Hanson 1996). The particulate form of methane monooxygenase contains copper, or both copper... 

Fox BG, Wa Froland, JE Dege, JD Lipscomb (1989) Methane monooxygenase from Methylosinus trichospo-rium OB3b. Purification and properties of a three-component system with a high specific activity from a type II methanotroph. J Biol Chem 264 10023-10033. 

Methanotrophs rely on the enzymatic system methane monooxygenase (MMO) to catalyze the first step in the metabolism of methane, shown in Eq. (1) (1, 14). 

Copper enzymes are involved in reactions with a large number of other, mostly inorganic substrates. In addition to its role in oxygen and superoxide activation described above, copper is also involved in enzymes that activate methane, nitrite and nitrous oxide. The structure of particulate methane mono-oxygenase from the methanotrophic bacteria Methylococcus capsulatus has been determined at a resolution of 2.8 A. It is a trimer with an a3P33 polypeptide arrangement. Two metal centres, modelled as mononuclear and dinuclear copper, are located in the soluble part of each P-subunit, which resembles CcOx subunit II. A third metal centre, occupied by Zn in the crystal, is located within the membrane. 

Oremland et al. [136] subsequently demonstrated that methane-oxidizing bacteria also had the capacity to co-oxidize methyl bromide by methane monooxygenase produced during the oxidation of methane to methanol. They also showed that methanotrophic soils that had a high capacity to oxidize methane degraded14C-labeled methyl bromide to 14C02. 

Methanotrophs Microbes that use methane as an electron donor. 

Two types of methane monooxygenases have been studied (1) soluble methane monooxygenase (sMMO) and (2) particulate (membrane-bound) methane monooxygenase (pMMO). The well-studied sMMO is produced by methanotrophs under copper-limiting conditions. All methanotrophs produce pMMO—found in intracytoplasmic membranes— but it is the less well-studied enzyme. 

The Biotrol methanotrophic bioreactor system is an ex situ remedial technology that uses methanotrophic bacteria to degrade contaminants in groundwater. Methanotrophs use methane... 

Methanotrophic biofilters are a biological technology for remediation aqueous- and liquid-phase organic contaminants, particularly chlorinated organics. This technology utilizes a type of bacteria, known as a methanotroph, that consumes methane as a nutrient source. 

The U.S. Department of Energy s Office of Technology Development has sponsored full-scale environmental restoration technology demonstrations since 1990. The Savannah River Site Integrated Demonstration focuses on the bioremediation of groundwater contaminated by chlorinated solvents. Several laboratories, including the Savannah River site, have demonstrated the ability of methanotrophic bacteria (i.e., those that oxidize methane) found in soil, sediment, and aqueous material, to completely degrade or mineralize chlorinated solvents. 

You need to purify a waste water stream containing a recalitrant compound, trichloroethene, present in fairly high concentrations, 100 yuM (13 ppm). If one can deliver this waste water into a well mixed tank (i.e., a continuously stirred tank reactor or CSTR) virtually saturated with methane at 500 yuM and oxygen at 1000 yuM and all other nutrients needed for microbial growth on methane, then one can build up a methanotroph population capable of degrading the trichloroethene by cometabolism to innocuous substances like C02 and H20 before the water is discharged. 

Calculate the steady-state output trichloroethene concentration (/tM) after the methanotrophs have increased their biomass to a steady state level (cell-m-3) assuming a tank with a volume of either V= 10 m3 or 50 m3. Assume you have a waste water flow, Q, of 5 m3 d l, a microbial inoculum with growth properties like those shown in Table 17.6 for the landfill-derived methane oxidizers, and a die-off coefficient b of 0.1 d . 

Once the methanotroph-containing CSR has been established, we expect it can cometabolically oxidize some of the TCE incidental to the use of the primary substrate, methane. The rate of TCE biotransformation is dictated by the effectiveness of the methane mono-oxygenase for interacting with TCE rather than methane. This enzymatic processing of TCE can be described using a Michaelis-Menten expression ... 

P 17.10 Do Soil Methanotrophs Degrade Significant Amounts of Atmospheric Methane ... 

Chang, W.-K., and C. S. Criddle, Experimental evaluation of a model for cometabolism Prediction of simultaneous degradation of trichloroethylene and methane by a methanotrophic mixed culture , Biotech. Bioeng., 56,492-501 (1997). 

Koh, S.-C., J. P. Bowman, and G. S. Sayler, Soluble methane monooxygenase production and trichloroethylene degradation by a type I methanotroph, Methylomonas methanica 68-1 , Appl. Environ. Microbiol., 59,960-967 (1993). 

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