A centrifuge tube reactor for the determination of bacterial methane oxidation enrichment factors without influence of diffusion related isotope fractionation.

Biotransformation of methane at landfill sites can be estimated by applying compound specific stable isotope analysis of methane from the anaerobic and the cover layer surface zone. Next to these two input parameters, merely the knowledge of the carbon isotopic fractionation of the bacterial methane oxidation in terms of the enrichment factor (ε) is required. However, many factors and conditions have been described to affect ε. These include temperature, the applied landfill cover, the type of expressed methane monooxygenase (MMO), and cell density. In this work we investigated the microbial methane oxidation with respect to temperature and type of methanotrophic enrichment culture. A newly designed setup was used to overcome potential CH4-substrate limitations such as diffusion that could affect the determined values of ε by improper and inhomogeneous mixing. The isotopic fractionation was determined based on the stable carbon isotope analysis of methane and carbon dioxide. The obtained value for isotopic fractionation was ε22°C = -0.0136 ±â€¯0.0036. Also for the first time, bulk stable isotope analysis of bacterial cell mass was performed by flow injection analysis isotope ratio mass spectrometry.

Applying reverse stable isotope labeling analysis by mid-infrared laser spectroscopy to monitor BDOC in recycled wastewater.

Biological stability of treated wastewater is currently determined by methods such as biological oxygen demand, ATP-quantification, or flow-cytometric cell counting. However, the continuous increase in water reclamation for wastewater reuse requires new methods for quantifying degradation of biodegradable dissolved organic carbon (BDOC) ranging from very small to high concentrations of dissolved organic carbon (DOC). Furthermore, direct activity measures or absolute concentrations of BDOC are needed that produce comparable and reproducible results in all laboratories. Measuring carbon mineralization by CO2 evolution presents a suitable approach for directly measuring the microbial degradation activity. In this work, we investigated the extent of BDOC in water samples from effluent of a wastewater treatment plant and after purification by ultrafiltration over 204 days. BDOC monitoring was performed with the recently introduced reverse stable isotope labeling (RIL) analysis using mid-infrared spectroscopy for the monitoring of microbial CO2 production. Average BDOC degradation rates ranged from 0.11 to 0.32 mg L-1 d-1 for wastewater treatment plant effluent and from 0.03 to 0.22 mg L-1 d-1 after ultrafiltration. BDOC was degraded over >90 days indicating the long-term instability of the DOC. Degradation experiments over 88 days revealed first order kinetic rate constants for BDOC which corresponded to 12.7 ·â€¯10-3 d-1 for wastewater treatment plant effluent and 2.7 ·â€¯10-3 d-1 after ultrafiltration, respectively. A thorough sensitivity analysis of the RIL showed that the method is very accurate and sensitive with method detection limits down to 10 µg·â€¯L-1 of measured CO2.

The monogenean Paradiplozoon ichthyoxanthon behaves like a micropredator on two of its hosts, as indicated by stable isotopes.

The analysis of stable isotopes of carbon and nitrogen has been used as a fingerprint for understanding the trophic interactions of organisms. Most of these studies have been applied to free-living organisms, while parasites have largely been neglected. Studies dealing with parasites so far have assessed the carbon and nitrogen signatures in endoparasites or ectoparasites of different hosts, without showing general trends concerning the nutritional relationships within host-parasite associations. Moreover, in most cases such systems involved a single host and parasite species. The present study is therefore the first to detail the trophic interactions of a freshwater monogenean-host model using δ13C and δ15N, where a single monogenean species infects two distinctly different hosts. Host fishes, Labeobarbus aeneus and Labeobarbus kimberleyensis from the Vaal Dam, South Africa, were assessed for the monogenean parasite Paradiplozoon ichthyoxanthon, individuals of which were removed from the gills of the hosts. The parasites and host muscle samples were analysed for signatures of δ13C and δ15N using an elemental analyser connected to an isotope ratio mass spectrometer. Host fish appear to use partly different food sources, with L. aeneus having slightly elevated δ13C signatures compared to L. kimberleyensis, and showed only small differences with regard to their nitrogen signatures, suggesting that both species range on the same trophic level. Carbon and nitrogen signatures in P. ichthyoxanthon showed that the parasites mirrored the small differences in dietary carbon sources of the host but, according to δ15N signatures, the parasite ranged on a higher trophic level than the hosts. This relationship resembles predator-prey relationships and therefore suggests that P. ichthyoxanthon might act as a micropredator, similar to blood-sucking arthropods such as mites and fleas.

Microwave-assisted nonionic surfactant extraction of aliphatic hydrocarbons from petroleum source rock.

The extraction of aliphatic hydrocarbons from petroleum source rock using nonionic surfactants with the assistance of microwave was investigated and the conditions for maximum yield were determined. The results showed that the extraction temperatures and kinetic rates have significant effects on extraction yields of aliphatic hydrocarbons. The optimum temperature for microwave-assisted nonionic surfactant extraction of aliphatic hydrocarbons from petroleum source rock was 105°C. The optimum extraction time for the aliphatic hydrocarbons was at 50 min. Concentration of the nonionic surfactant solution and irradiation power had significant effect on the yields of aliphatic hydrocarbons. The yields of the analytes were much higher using microwave assisted nonionic surfactant extraction than with Soxhlet extraction. The recoveries of the n-alkanes and acyclic isoprenoid hydrocarbons for GC-MS analysis from the extractant nonionic surfactant solution by in-tube extraction (ITEX 2) with a TENAX TA adsorbent were found to be efficient. The results show that microwave-assisted nonionic surfactant extraction (MANSE) is a good and efficient green analytical preparatory technique for geochemical evaluation of petroleum source rock.