Rayleigh-Based Concept to Tackle Strong Hydrogen Fractionation in Dual Isotope AnalysisThe Example of Ethylbenzene Degradation by <i>Aromatoleum aromaticum</i>

Compound-specific isotope analysis (CSIA) is a state-of-the-art analytical tool that can be used to establish and quantify biodegradation of pollutants such as BTEX compounds at contaminated field sites. Using isotopes of two elements and characteristic Lambda values (Λ) in dual-isotope-plots can provide insight into reaction mechanisms because kinetic isotope effects (KIEs) of both elements are reflected. However, the concept’s validity in the case of reactions that show strong isotope fractionation needs to be examined. The anaerobic ethylbenzene degradation pathway of <i>Aromatoleum aromaticum</i> is initiated by the ethylbenzene dehydrogenase-catalyzed monohydroxylation of the benzylic carbon atom. Measurements of stable isotope ratios revealed highly pronounced hydrogen fractionation, which could not be adequately described by the classical Rayleigh approach. This study demonstrates the nonlinear behavior of hydrogen isotope ratios caused by anaerobic ethylbenzene hydroxylation both mathematically and experimentally, develops alternative dual plots to enable the comparison of reactions by considering the reacting atoms, and illustrates the importance of the stereochemical aspects of substrate and product for the quantification of hydrogen fractionation in an enzymatic reaction. With regard to field application, proposals for an improved CSIA evaluation procedure with respect to pronounced hydrogen enrichment are given

Compound-Specific Isotope Analysis as a Tool To Characterize Biodegradation of Ethylbenzene

This study applied one- and two-dimensional compound-specific isotope analysis (CSIA) for the elements carbon and hydrogen to assess different means of microbial ethylbenzene activation. Cultures incubated under nitrate-reducing conditions showed significant carbon and highly pronounced hydrogen isotope fractionation of comparable magnitudes, leading to nearly identical slopes in dual-isotope plots. The results imply that <i>Georgfuchsia toluolica</i> G5G6 and an enrichment culture dominated by an <i>Azoarcus</i> species activate ethylbenzene by anaerobic hydroxylation catalyzed by ethylbenzene dehydrogenase, similar to <i>Aromatoleum aromaticum</i> EbN1. The isotope enrichment pattern in dual plots from two strictly anaerobic enrichment cultures differed considerably from those for benzylic hydroxylation, indicating an alternative anaerobic activation step, most likely fumarate addition. Large hydrogen fractionation was quantified using a recently developed Rayleigh-based approach considering hydrogen atoms at reactive sites. Data from nine investigated microbial cultures clearly suggest that two-dimensional CSIA in combination with the magnitude of hydrogen isotope fractionation is a valuable tool to distinguish ethylbenzene degradation and may be of practical use for monitoring natural or technological remediation processes at field sites

Analysis and exploitation of resource efficiency potentials in industrial small and medium-sized enterprises – Experiences with the EDIT Value Tool in Central Europe

Material and energy costs represent about 50% of the operating costs incurred by European small and medium-sized enterprises (SMEs). Although the potential for resource efficiency improvements is high, the necessary awareness and human resource capacities to explore this potential are limited. Existing tools for exploration of resource efficiency improvement potentials have several shortcomings: they are either tool-driven, of a solely qualitative nature or do not address all levels of a business. Users of such tools therefore miss important improvement opportunities. In order to overcome these limitations and to systematically identify, quantify and fully explore resource efficiency improvement potentials, an international team developed and tested a new comprehensive, needs-driven and quantitative diagnosis tool named the ‘EDIT Value Tool.’ This tool can be used to perform initial diagnoses for companies. The EDIT Value Tool was piloted in eighteen manufacturing SMEs in six Central European countries. Evaluation of the test results showed that the tool is effective in helping company personnel to identify the main weaknesses and the potentials for company improvements. The tool achieves this by evaluating a business's characteristics: its stakeholder values, the corporate strategy to implement its mission and vision, assessment of the effectivity of the company's management systems, processes and products. The benefits of using the EDIT Value Tool that were of most benefit to the companies were the proposed changes to corporate technology and management. The collection of quantitative and qualitative data helped company personnel to develop new perspectives on how to monitor and to improve resource efficiency and to increase awareness of and commitment to more sustainable manufacturing systems