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Controls on in situ methanotroph activity are not well understood. One potentially important parameter is copper (Cu) because this metal is at the centre of particulate methane monooxygenase (pMMO), the most active enzyme involved in oxidizing methane to methanol. Furthermore, Cu-to-cell ratios influence the relative expression of pMMO versus the alternate soluble MMO (sMMO) in some species. Most methanotroph studies have only assessed readily soluble forms of Cu (e.g., CuCl2) atypical of real methanotroph habitats and there is a dearth of activity data associated with more common environmental Cu sources. Here we quantified sMMO activity and growth kinetics in Methylosinus trichosporium OB3b, an organism that expresses both pMMO and sMMO, when grown on Cu-minerals with differing dissolution equilibria to assess how mineral source and methanobactin (mb) influences growth. Mb is a molecule produced by M. trichosporium OB3b that has a high affinity for Cu, reduces Cu toxicity, mediates Cu uptake and may be key to Cu availability in terrestrial systems. Abiotic Cu-dissolution experiments showed that Cu release is affected by mb level, although mb only enhances Cu dissolution from sparingly soluble minerals, such as CuO and to a greater extent CuCO3 ·Cu(OH)2· However, the two minerals affected M. trichosporium OB3b growth very differently. Cells grew without growth lag and with active pMMO on CuCO3 ·Cu(OH)2, regardless of the amount of mineral supplied (<500 µmoles Cu-total L-1). In contrast, they also grew well with CuO (< 50 µmoles Cu-total L-1), but instead had active sMMO, although sMMO activity was conditionally suppressed by supplemental mb and-or direct cell-mineral contact. Mb additions significantly increased growth rates (p<0.05) with both minerals. Results show mb broadly stimulates growth, but Cu mineralogy and mb dictate whether sMMO or pMMO is active in the cells. This has implications to in situ bioremediation and other studies on methanotroph function in terrestrial systems. [ABSTRACT FROM AUTHOR]

In many nations industrial scale AD of non-agricultural waste materials (such as MSW) has not yet reached its full potential, often constrained by the lack of secure, inexpensive, high quality AD feedstocks, and markets for the resulting digestate material. We tested the output material of a high throughput novel industrial process to define its potential as an AD feedstock (based on quality and consistency). This process, designed to circumvent the constraints of source segregation while still generating segregated waste streams, resulted in the production of a temporally homogenous fibrous material with: an average moisture content of 44.2 (±2.33)%; C:N ratio of ~32.9:1 (±3.46:1), C:P ratio of ~228:1 and gross calorific value of 17.4 (±0.29) MJ/kg(DM). This material provided a CH4 yield of between 201 and 297 m³ CH4/tonne(DM) (271-401 m³ CH4/tonne(vs)) comparable to commonly used AD feedstocks. Material contaminant levels were temporally consistent (P > 0.05), (average values being Cd 0.63 (±0.19), Cu 56.3 (±7.45), Crtot 51.4 (±4.41), Hg < 0.3, Ni 28.9 (±5.17), Pb 79.2 (±23.71), Zn 202 (±44.5), total polyaromatic hydrocarbons (PAH) 2.2 (±0.3), and total polychlorinated biphenyls (PCB) (<0.2) mg/kg(DM)). Calculated digestate contaminant levels were below the median contaminant threshold limits for anaerobic digestates of all countries within the European Union i.e. of Cd 3.35, Cu 535, Crtot 535, Hg 8.15, Ni 185, Pb 397.5, Zn 2100 mg/kg(DM). We suggest that novel high throughput processes that produce high quality AD feedstocks, may have a place in further diversion of waste from landfill. [ABSTRACT FROM AUTHOR]

Hydrocarbons are common constituents of surface, shallow, and deep-subsurface environments. Under anaerobic conditions, hydrocarbons can be degraded to methane by methanogenic microbial consortia. This degradation process is widespread in the geosphere. In comparison with other anaerobic processes, methanogenic hydrocarbon degradation is more sustainable over geological time scales because replenishment of an exogenous electron acceptor is not required. As a consequence, this process has been responsible for the formation of the world's vast deposits of heavy oil, which far exceed conventional oil assets such as those found in the Middle East. Methanogenic degradation is also a potentially important component of attenuation in hydrocarbon contamination plumes. Studies of the organisms, syntrophic partnerships, mechanisms, and geochemical signatures associated with methanogenic hydrocarbon degradation have identified common themes and diagnostic markers for this process in the subsurface. These studies have also identified the potential to engineer methanogenic processes to enhance the recovery of energy assets as biogenic methane from residual oils stranded in petroleum systems., (Copyright 2010 Elsevier Inc. All rights reserved.)

A novel stable isotope titration approach was developed to determine the contributions to total methane production made by CO(2) reduction and the disproportionation of acetate in anoxic environments. (13)CH(4), (12)CH(4), (13)CO(2) and (12)CO(2) production rates were measured in the head space of replicate anaerobic microcosms titrated with increasing amounts of (13)C-labelled substrates. The contribution of CO(2) reduction was calculated from the linear relationship between ratios of labelled and total CH(4) production and ratios of labelled and total CO(2) after the addition of (13)C-bicarbonate. In the case of acetoclastic methanogenesis rates of (13)CH(4) and (12)CH(4) production were fitted to a model based on an assumption that the relationship between the concentration of (13)C-labelled acetate and the rates of labelled and unlabelled methane production followed Michaelis-Menten kinetics. A comparison of the raw data with the model supported the assumption and provided both an estimate of the contribution of acetate to methane production and an estimate of the size of the indigenous acetate pool without the need to measure acetate directly. The method was applied to a freshwater sediment in the English Lake District where it was found that 66.3% (se 4.9) of methane production was due to acetate disproportionation and 28.9% (se 1.9) of methane production resulted from CO(2) reduction. This is in agreement with theoretical predictions and other empirical measurements of methanogenesis.