Anaerobic degradation of 2-propanol: Laboratory and pilot-scale studies

The anaerobic degradation of 2-propanol, an important industrial solvent, was scaled-up from batch assays to a pilot expanded granular sludge bed (EGSB) reactor at 25 °C. Batch studies indicated that 2-propanol followed Haldane kinetics, with a maximum rate at 10 g COD L−1. Concentrations as high as 25 g COD L−1 did not inhibit the degradation of ethanol, a common co-solvent. Similar specific methanogenic activities (SMA) were obtained for water-solvent and water-brewery sludges (88 and 77 ml CH4 g-VS−1 d−1 at 5 g COD L−1). Continuous degradation showed a lag-phase of three weeks with water-brewery sludge. Increases in 2-propanol load from 0.05 to 0.18 kg COD kg-VS−1 d−1 caused a shift from the consumption of soluble matter to methane production, indicating polyhydroxybutyrates (PHB) accumulation. Conversely, smooth increases of up to 0.29 kg COD kg-VS−1 d−1 allowed 2-propanol degradation without PHB accumulation. The slowdown rate of 2-propanol-oxidizer and acetate-utilizing methanogen bacteria below 20 °C adversely impacted both removal and CH4 yield

THE PROCESSES OF METHANE-FORMATION AND METHANE-OXIDATION IN THE FREEZING SOILS OF THE KOLYMSKY LOWLAND

The investigations of the different aspects of biogeochemistry of the methane cycle in freezing soils of the Kolymsky Lowland have been performed. Revealed have been the types of soils, being the main sources of methane in the atmosphere on the given territory; the activity of the methane-forming and methane-oxidation microbe communities in the thawed layer of the soil has been determined; the data on spreading, number and species variety of methanogenes and methanotrophs in the frozen soils of the hydromorph row have been received; the speeds of the processes of formation and oxidation of methane under the modeling conditions have been evaluated. The data on the methane flows from the frozen soils of the Kolymsky lowland, have been obtained and the effort of evaluating the methane emission scale from this territory has been taken up. The materials have been used for the evaluation of the natural and technogenous methane flows from the soil. The main results have been used in performing a special course "Radioisotope Methods of Study of Biogeochemical Activity of Microorganisms in Soil" in the Pushchino State UniversityAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Intracellular PHB conversion in a type II methanotroph studied by 13 C NMR

Poly-g-hydroxybutyrate (PHB) formation under aerobic conditions via incorporation of [13C-2]acetate as a cosubstrate and its intracellular degradation under anaerobic conditions in a Type II methanotroph was studied by 13C NMR. During PHB synthesis in the presence of labelled acetate, low levels of g-hydroxybutyrate, butyrate, acetone, isopropanol, 2,3-butanediol and succinate were observed. Subsequent anaerobic PHB breakdown showed enhanced levels of these products at the expense of PHB. Fermentative metabolism occurring during anaerobic PHB degradation was confirmed in experiments with fully 13C-enriched cells, which were grown on 13C-labelled methane. g-hydroxybutyrate, butyrate, acetate, acetone, isopropanol, 2,3-butanediol and succinate were detected as multiple 13C-labelled compounds in the culture medium. Our results suggest that intracellular PHB degradation can be used as a reserve energy source by methanotrophs under anoxic conditions

Microaerobic and anaerobic metabolism of a Methylocystis parvus strain isolated from a denitrifying bioreactor

An obligate methanotrophic bacterium, strain MTS, was isolated from a methane-fed microaerobic denitrifying bioreactor. 16S rRNA and DNA–DNA hybridization analysis revealed that this organism was most closely related to Methylocystis parvus, a Type II methanotroph, belonging to the a-subclass of the Proteobacteria. The metabolism of the bacterium under microaerobic and anaerobic conditions was studied by 13C-NMR. 13C-labelled poly-ß-hydroxybutyrate (PHB) formation occurred in cell suspensions incubated with 13C-labelled methane at low (5–10%) oxygen concentration. Under these conditions low levels of succinate, acetate and 2,3-butanediol were formed and excreted into the culture medium. Intracellular PHB degradation was observed in intact cells under anaerobic conditions in the absence of an exogenous carbon source during a long-term incubation of 90 days. Multiple 13C-labelled ß-hydroxybutyrate, butyrate, acetate, acetone, isopropanol, 2,3-butanediol and succinate were identified as products in in vivo13C-NMR spectra and in the spectra of culture medium during the dynamic PHB degradation. The isolated obligate methanotroph clearly shows a fermentative metabolism of PHB under anaerobic conditions. The excreted products may serve as substrates for denitrifying bacteri

The effect of oxygen on methanol oxidation by an obligate metahnotrophic bacterium studied by in vivo 13C nuclear magnetic resonance spectroscopy

13C NMR was used to study the effect of oxygen on methanol oxidation by a type II methanotrophic bacterium isolated from a bioreactor in which methane was used as electron donor for denitrification. Under high (35-25€oxygen conditions the first step of methanol oxidation to formaldehyde was much faster than the following conversions to formate and carbon dioxide. Due to this the accumulation of formaldehyde led to a poisoning of the cells. A more balanced conversion of 13C-labelled methanol to carbon dioxide was observed at low (1-5€oxygen concentrations. In this case, formaldehyde was slowly converted to formate and carbon dioxide. Formaldehyde did not accumulate to inhibitory levels. The oxygen-dependent formation of formaldehyde and formate from methanol is discussed kinetically and thermodynamically

Microbial Controls on Methane Fluxes from a Polygonal Tundra of the Lena Delta, Siberia

Permafrost soils of high-latitude wetlands are an important source of atmospheric methane. In order to improve our understanding of the large seasonal fluctuations of trace gases, we measured the CH4 fluxes as well as the fundamental processes of CH4 production and CH4 oxidation under in situ conditions in a typical polygon tundra in the Lena Delta, Siberia. Net CH4 fluxes were measured from the polygon depression and from the polygon rim from the end of May to the beginning of September 1999. The mean flux rate of the depression was 53.2 ± 8.7 mg CH4 m−2 d−1 with maximum in mid-July (100–120 mg CH4 m−2 d−1), whereas the mean flux rate of the dryer rim part of the polygon was 4.7 ± 2.5 CH4 m−2 d−1. The microbial CH4 production and oxidation showed significant differences during the vegetation period. The CH4 production in the upper soil horizon of the polygon depression was about 10 times higher (38.9 ± 2.9 nmol CH4 h−1 g−1) in July than in August (4.7 ± 1.3 nmol CH4 h−1 g−1). The CH4 oxidation behaved exactly in reverse: the oxidation rate of the upper soil horizon was low (1.9 ± 0.3 nmol CH4 h−1 g−1) in July compared to the activity in August (max. 7.0 ± 1.3 nmol CH4 h−1 g−1). The results indicated clearly an interaction between the microbiological processes with the observed seasonal CH4 fluctuations. However, the CH4 production is primarily substrate dependent, while the oxidation is dependent on the availability of oxygen. The temperature plays only a minor role in both processes, probably because the organisms are adapted to extreme temperature conditions of the permafrost. For the understanding of the carbon dynamics in permafrost soils, a differentiated small-scale view of the microbiological processes and the associated modes of CH4 fluxes is necessary, especially at key locations such as the Siberian Arctic

Stable isotope switching (SIS): a new stable isotope probing (SIP) approach to determine carbon flow in the soil food web and dynamics in organic matter pools

RATIONALE: Recent advances in stable isotope probing (SIP) have allowed direct linkage of microbial population structure and function. This paper details a new development of SIP, Stable Isotope Switching (SIS), which allows the simultaneous assessment of carbon (C) uptake, turnover and decay, and the elucidation of soil food webs within complex soils or sedimentary matrices. METHODS: SIS utilises a stable isotope labelling approach whereby the 13C-labelled substrate is switched part way through the incubation to a natural abundance substrate. A 13CH4 SIS study of landfill cover soils from Odcombe (Somerset, UK) was conducted. Carbon assimilation and dissimilation processes were monitored through bulk elemental analysis isotope ratio mass spectrometry and compound-specific gas chromatography/combustion/isotope ratio mass spectrometry, targeting a wide range of biomolecular components including: lipids, proteins and carbohydrates. RESULTS: Carbon assimilation by primary consumers (methanotrophs) and sequential assimilation into secondary (Gram-negative and -positive bacteria) and tertiary consumers (Eukaryotes) was observed. Up to 45% of the bacterial membrane lipid C was determined to be directly derived from CH4 and at the conclusion of the experiment ca. 50% of the bulk soil C derived directly from CH4 was retained within the soil. CONCLUSIONS: This is the first estimate of soil organic carbon derived from CH4 and it is comparable with levels observed in lakes that have high levels of benthic methanogenesis. SIS opens the way for a new generation of SIP studies aimed at elucidating total C dynamics (incorporation, turnover and decay) at the molecular level in a wide range of complex environmental and biological matrices

Phosphorus starvation and luxury uptake in green microalgae revisited

Phosphorus (P) is central to storing and transferring energy and information in living cells, including those of microalgae. Many microalgal species dwelling in low P environments are naturally equipped to take up and store P whenever it becomes available through a complex phenomenon known as “luxury P uptake.” Its research is required for better understanding of the nutrient geochemical cycles in aquatic environments but also for biotechnological applications such as sequestration of nutrients from wastewater and production of algal fertilizers. Here, we report on our recent insights into luxury P uptake and polyphosphate formation originating from physiological, ultrastructural, and transcriptomic evidence. The cultures pre-starved of P and re-fed with inorganic phosphate (Pi) exhibited a bi-phasic kinetics of Pi uptake comprising fast (1–2 h after re-feeding) and slow (1–3 d after re-feeding) phases. The rate of Pi uptake in the fast phase was ca. 10 times higher than in the slow phase with an opposite trend shown for the cell division rate. The transient peak of polyphosphate accumulation was determined 2–4 h after re-feeding and coincided with the period of slow cell division and fast Pi uptake. In this phase, the microalgal cells reached the highest P content (up to 5% of dry cell weight). The P re-feeding also reversed the characteristic changes in cell lipids induced by P starvation, namely increase in the major membrane glycolipid (DGDG/MGDG) ratio and betaine lipids. These changes were reversed upon Pi re-feeding of the starved culture. Electron microscopy revealed the ordered organization of vacuolar polyphosphate indicative of the possible involvement of an enzyme (complex) in their synthesis. A candidate gene encoding a protein similar to the vacuolar transport chaperone (VTC) protein, featuring an expression pattern corresponding to polyphosphate accumulation, was revealed. Implications of the findings for efficient biocapture of phosphorus are discussed

Phosphorus starvation and luxury uptake in green microalgae revisited

Phosphorus (P) is central to storing and transferring energy and information in living cells, including those of microalgae. Many microalgal species dwelling in low P environments are naturally equipped to take up and store P whenever it becomes available through a complex phenomenon known as “luxury P uptake.” Its research is required for better understanding of the nutrient geochemical cycles in aquatic environments but also for biotechnological applications such as sequestration of nutrients from wastewater and production of algal fertilizers. Here, we report on our recent insights into luxury P uptake and polyphosphate formation originating from physiological, ultrastructural, and transcriptomic evidence. The cultures pre-starved of P and re-fed with inorganic phosphate (Pi) exhibited a bi-phasic kinetics of Pi uptake comprising fast (1–2 h after re-feeding) and slow (1–3 d after re-feeding) phases. The rate of Pi uptake in the fast phase was ca. 10 times higher than in the slow phase with an opposite trend shown for the cell division rate. The transient peak of polyphosphate accumulation was determined 2–4 h after re-feeding and coincided with the period of slow cell division and fast Pi uptake. In this phase, the microalgal cells reached the highest P content (up to 5% of dry cell weight). The P re-feeding also reversed the characteristic changes in cell lipids induced by P starvation, namely increase in the major membrane glycolipid (DGDG/MGDG) ratio and betaine lipids. These changes were reversed upon Pi re-feeding of the starved culture. Electron microscopy revealed the ordered organization of vacuolar polyphosphate indicative of the possible involvement of an enzyme (complex) in their synthesis. A candidate gene encoding a protein similar to the vacuolar transport chaperone (VTC) protein, featuring an expression pattern corresponding to polyphosphate accumulation, was revealed. Implications of the findings for efficient biocapture of phosphorus are discussed. © 2019 Elsevier B.V

The microbial methane cycle

This special issue highlights several recent discoveries in the microbial methane cycle, including the diversity and activity of methanotrophic bacteria in special habitats, distribution and contribution of the newly discovered Verrucomicrobia, metabolism of methane and related one-carbon compounds such as methanol and methylamine in freshwater and marine environments, methanol and methane-dependent nitrate reduction, the relationships of methane cycle microorganisms with plants and animals, and the environmental factors that regulate microbial processes of the methane cycle. These articles also highlight the plethora of new organisms and metabolism relating to the methane cycle that have been discovered in recent years and outline the many questions in the methane cycle that still need to be addressed. It is clear that despite a tremendous amount of research on the biology of the methane cycle, the microbes involved in catalysing methane production and consumption harbour many secrets that need to be disclosed in order for us to fully understand how the biogeochemical methane cycle is regulated in the environment, and for us to make future predictions about the global sources and sinks of methane and how anthropogenic changes impact on the cycling of this important greenhouse gas