Chemical Recycling of Polyethylene by Tandem Catalytic Conversion to Propylene.

Although polyethylene (PE) and polypropylene (PP) are by far the world's largest volume plastics, only a tiny fraction of these energy-rich polyolefins are currently recycled. Depolymerization of PE to its constituent monomer, ethylene, is highly endothermic and conventionally accessible only through unselective, high-temperature pyrolysis. Here, we provide experimental demonstrations of our recently proposed tandem catalysis strategy, which uses ethylene to convert PE to propylene, the commodity monomer used to make PP. The approach combines rapid olefin metathesis with rate-limiting isomerization. Monounsaturated PE is progressively disassembled at modest temperatures via many consecutive ethenolysis events, resulting selectively in propylene. Fully saturated PE can be converted to unsaturated PE starting with a single transfer dehydrogenation to ethylene, which produces a small amount of ethane (1 equiv per dehydrogenation event). These principles are demonstrated using both homogeneous and heterogeneous catalysts. While selectivity under batch conditions is limited at high conversion by the formation of an equilibrium mixture of olefins, high selectivity to propylene (≥94%) is achieved in a semicontinuous process due to the continuous removal of propylene from the reaction mixture.

Quantity and fate of synthetic microfiber emissions from apparel washing in California and strategies for their reduction.

Synthetic microfibers have been identified as the most prevalent type of microplastic in samples from aquatic, atmospheric, and terrestrial environments across the globe. Apparel washing has shown to be a major source of microfiber pollution. We used California as a case study to estimate the magnitude and fate of microfiber emissions, and to evaluate potential mitigation approaches. First, we quantified synthetic microfiber emissions and fate from apparel washing in California by developing a material flow model which connects California-specific data on synthetic fiber consumption, apparel washing, microfiber generation, and wastewater and biosolid management practices. Next, we used the model to assess the effectiveness of different interventions to reduce microfiber emissions to natural environments. We estimate that in 2019 as much as 2.2 kilotons (kt) of synthetic microfibers were generated by apparel washing in California, a 26% increase since 2008. The majority entered terrestrial environments (1.6 kt), followed by landfills (0.4 kt), waterbodies (0.1 kt), and incineration (0.1 kt). California's wastewater treatment network was estimated to divert 95% of microfibers from waterbodies, mainly to terrestrial environments and primarily via land application of biosolids. Our analysis also reveals that application of biosolids on agricultural lands facilitates a directional flow of microfibers from higher-income urban counties to lower-income rural communities. Without interventions, annual synthetic microfiber emissions to California's natural environments are expected to increase by 17% to 2.1 kt by 2026. Further increasing the microfiber retention efficiency at the wastewater treatment plant would increase emissions to terrestrial environments, which suggests that microfibers should be removed before entering the wastewater system. In our model, full adoption of in-line filters in washing machines decreased annual synthetic microfiber emissions to natural environments by 79% to 0.5 kt and offered the largest reduction of all modeled scenarios.

Synthetic microfiber emissions to land rival those to waterbodies and are growing.

Synthetic microfibers are found virtually everywhere in the environment, but emission pathways and quantities are poorly understood. By connecting regionalized global datasets on apparel production, use, and washing with emission and retention rates during washing, wastewater treatment, and sludge management, we estimate that 5.6 Mt of synthetic microfibers were emitted from apparel washing between 1950 and 2016. Half of this amount was emitted during the last decade, with a compound annual growth rate of 12.9%. Waterbodies received 2.9 Mt, while combined emissions to terrestrial environments (1.9 Mt) and landfill (0.6 Mt) were almost as large and are growing. Annual emissions to terrestrial environments (141.9 kt yr-1) and landfill (34.6 kt yr-1) combined are now exceeding those to waterbodies (167.2 kt yr-1). Improving access to wastewater treatment is expected to further shift synthetic microfiber emissions from waterbodies to terrestrial environments. Preventing emissions at the source would therefore be a more effective mitigation measure.

Environmental Benefits of Novel Nonhuman Food Inputs to Salmon Feeds.

Global population growth and changing diets increase the importance, and challenges, of reducing the environmental impacts of food production. Farmed seafood is a relatively efficient way to produce protein and has already overtaken wild fisheries. The use of protein-rich food crops, such as soy, instead of fishmeal in aquaculture feed diverts these important protein sources away from direct human consumption and creates new environmental challenges. Single cell proteins (SCPs), including bacteria and yeast, have recently emerged as replacements for plant-based proteins in salmon feeds. Attributional life cycle assessment is used to compare salmon feeds based on protein from soy, methanotrophic bacteria, and yeast ingredients. All ingredients are modeled at the industrial production scale and compared based on seven resource use and emissions indicators. Yeast protein concentrate showed drastically lower impacts in all categories compared to soy protein concentrate. Bacteria meal also had lower impacts than soy protein concentrate for five of the seven indicators. When these target meals were incorporated into complete feeds the relative trends remain fairly constant, but benefits of the novel ingredients are dampened by high impacts from the nontarget ingredients. Particularly, primary production requirements (PPR) are about equal and constant across all feeds for both analyses since PPR was driven by fishmeal and oil. The bacteria-based feed has the highest climate change impacts due to the use of methane to feed the bacteria who then release carbon dioxide. Overall, the results of this study suggest that incorporating SCP ingredients into salmon feeds can help reduce the environmental impacts of salmon production. Continued improvements in SCP production would further increase the sustainability of salmon farming.

Production, use, and fate of all plastics ever made.

Plastics have outgrown most man-made materials and have long been under environmental scrutiny. However, robust global information, particularly about their end-of-life fate, is lacking. By identifying and synthesizing dispersed data on production, use, and end-of-life management of polymer resins, synthetic fibers, and additives, we present the first global analysis of all mass-produced plastics ever manufactured. We estimate that 8300 million metric tons (Mt) as of virgin plastics have been produced to date. As of 2015, approximately 6300 Mt of plastic waste had been generated, around 9% of which had been recycled, 12% was incinerated, and 79% was accumulated in landfills or the natural environment. If current production and waste management trends continue, roughly 12,000 Mt of plastic waste will be in landfills or in the natural environment by 2050.

Development of rubber-enriched dandelion varieties by metabolic engineering of the inulin pathway.

Natural rubber (NR) is an important raw material for a large number of industrial products. The primary source of NR is the rubber tree Hevea brasiliensis, but increased worldwide demand means that alternative sustainable sources are urgently required. The Russian dandelion (Taraxacum koksaghyz Rodin) is such an alternative because large amounts of NR are produced in its root system. However, rubber biosynthesis must be improved to develop T. koksaghyz into a commercially feasible crop. In addition to NR, T. koksaghyz also produces large amounts of the reserve carbohydrate inulin, which is stored in parenchymal root cell vacuoles near the phloem, adjacent to apoplastically separated laticifers. In contrast to NR, which accumulates throughout the year even during dormancy, inulin is synthesized during the summer and is degraded from the autumn onwards when root tissues undergo a sink-to-source transition. We carried out a comprehensive analysis of inulin and NR metabolism in T. koksaghyz and its close relative T. brevicorniculatum and functionally characterized the key enzyme fructan 1-exohydrolase (1-FEH), which catalyses the degradation of inulin to fructose and sucrose. The constitutive overexpression of Tk1-FEH almost doubled the rubber content in the roots of two dandelion species without any trade-offs in terms of plant fitness. To our knowledge, this is the first study showing that energy supplied by the reserve carbohydrate inulin can be used to promote the synthesis of NR in dandelions, providing a basis for the breeding of rubber-enriched varieties for industrial rubber production.

Life Cycle Assessment of Solar Photovoltaic Microgrid Systems in Off-Grid Communities.

Access to a reliable source of electricity creates significant benefits for developing communities. Smaller versions of electricity grids, known as microgrids, have been developed as a solution to energy access problems. Using attributional life cycle assessment, this project evaluates the environmental and energy impacts of three photovoltiac (PV) microgrids compared to other energy options for a model village in Kenya. When normalized per kilowatt hour of electricity consumed, PV microgrids, particularly PV-battery systems, have lower impacts than other energy access solutions in climate change, particulate matter, photochemical oxidants, and terrestrial acidification. When compared to small-scale diesel generators, PV-battery systems save 94-99% in the above categories. When compared to the marginal electricity grid in Kenya, PV-battery systems save 80-88%. Contribution analysis suggests that electricity and primary metal use during component, particularly battery, manufacturing are the largest contributors to overall PV-battery microgrid impacts. Accordingly, additional savings could be seen from changing battery manufacturing location and ensuring end of life recycling. Overall, this project highlights the potential for PV microgrids to be feasible, adaptable, long-term energy access solutions, with health and environmental advantages compared to traditional electrification options.

Does centrifugation matter? Centrifugal force and spinning time alter the plasma metabolome.

BACKGROUND: Centrifugation is an indispensable procedure for plasma sample preparation, but applied conditions can vary between labs. AIM: Determine whether routinely used plasma centrifugation protocols (1500×g 10 min; 3000×g 5 min) influence non-targeted metabolomic analyses. METHODS: Nuclear magnetic resonance spectroscopy (NMR) and High Resolution Mass Spectrometry (HRMS) data were evaluated with sparse partial least squares discriminant analyses and compared with cell count measurements. RESULTS: Besides significant differences in platelet count, we identified substantial alterations in NMR and HRMS data related to the different centrifugation protocols. CONCLUSION: Already minor differences in plasma centrifugation can significantly influence metabolomic patterns and potentially bias metabolomics studies.

Conformational Restriction and Enantioseparation Increase Potency and Selectivity of Cyanoguanidine-Type Histamine H4 Receptor Agonists.

2-Cyano-1-[4-(1H-imidazol-4-yl)butyl]-3-[2-(phenylsulfanyl)ethyl]guanidine (UR-PI376, 1) is a potent and selective agonist of the human histamine H4 receptor (hH4R). To gain information on the active conformation, we synthesized analogues of 1 with a cyclopentane-1,3-diyl linker. Affinities and functional activities were determined at recombinant hHxR (x: 1-4) subtypes on Sf9 cell membranes (radioligand binding, [(35)S]GTPγS, or GTPase assays) and in part in luciferase assays on human or mouse H4R (HEK-293 cells). The most potent H4R agonists among 14 racemates were separated by chiral HPLC, yielding eight enantiomerically pure compounds. Configurations were assigned based on X-ray structures of intermediates and a stereocontrolled synthetic pathway. (+)-2-Cyano-1-{[trans-(1S,3S)-3-(1H-imidazol-4-yl)cyclopentyl]methyl}-3-[2-(phenylsulfanyl)ethyl]guanidine ((1S,3S)-UR-RG98, 39a) was the most potent H4R agonist in this series (EC50 11 nM; H4R vs H3R, >100-fold selectivity; H1R, H2R, negligible activities), whereas the optical antipode proved to be an H4R antagonist ([(35)S]GTPγS assay). MD simulations confirmed differential stabilization of the active and inactive H4R state by the enantiomers.

Investigating the Energy-Water Usage Efficiency of the Reuse of Treated Municipal Wastewater for Artificial Groundwater Recharge.

This project investigates the energy-water usage efficiency of large scale civil infrastructure projects involving the artificial recharge of subsurface groundwater aquifers via the reuse of treated municipal wastewater. A modeling framework is introduced which explores the various ways in which spatially heterogeneous variables such as topography, landuse, and subsurface infiltration capacity combine to determine the physical layout of proposed reuse system components and their associated process energy-water demands. This framework is applied to the planning and evaluation of the energy-water usage efficiency of hypothetical reuse systems in five case study regions within the State of California. Findings from these case study analyses suggest that, in certain geographic contexts, the water requirements attributable to the process energy consumption of a reuse system can exceed the volume of water that it is able to recover by as much as an order of magnitude.

Molecular Mechanisms by Which a Fucus vesiculosus Extract Mediates Cell Cycle Inhibition and Cell Death in Pancreatic Cancer Cells.

Pancreatic cancer is one of the most aggressive cancer entities, with an extremely poor 5-year survival rate. Therefore, novel therapeutic agents with specific modes of action are urgently needed. Marine organisms represent a promising source to identify new pharmacologically active substances. Secondary metabolites derived from marine algae are of particular interest. The present work describes cellular and molecular mechanisms induced by an HPLC-fractionated, hydrophilic extract derived from the Baltic brown seaweed Fucus vesiculosus (Fv1). Treatment with Fv1 resulted in a strong inhibition of viability in various pancreatic cancer cell lines. This extract inhibited the cell cycle of proliferating cells due to the up-regulation of cell cycle inhibitors, shown on the mRNA (microarray data) and protein level. As a result, cells were dying in a caspase-independent manner. Experiments with non-dividing cells showed that proliferation is a prerequisite for the effectiveness of Fv1. Importantly, Fv1 showed low cytotoxic activity against non-malignant resting T cells and terminally differentiated cells like erythrocytes. Interestingly, accelerated killing effects were observed in combination with inhibitors of autophagy. Our in vitro data suggest that Fv1 may represent a promising new agent that deserves further development towards clinical application.

Marine pollution. Plastic waste inputs from land into the ocean.

Plastic debris in the marine environment is widely documented, but the quantity of plastic entering the ocean from waste generated on land is unknown. By linking worldwide data on solid waste, population density, and economic status, we estimated the mass of land-based plastic waste entering the ocean. We calculate that 275 million metric tons (MT) of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million MT entering the ocean. Population size and the quality of waste management systems largely determine which countries contribute the greatest mass of uncaptured waste available to become plastic marine debris. Without waste management infrastructure improvements, the cumulative quantity of plastic waste available to enter the ocean from land is predicted to increase by an order of magnitude by 2025.

Synthesis and functional characterization of imbutamine analogs as histamine H3 and H4 receptor ligands.

Imbutamine (4-(1H-imidazol-4-yl)butanamine) is a potent histamine H3 (H3R) and H4 receptor (H4R) agonist (EC50 values: 3 and 66 nM, respectively). Aiming at improved selectivity for the H4R, the imidazole ring in imbutamine was methyl-substituted or replaced by various differently substituted heterocycles (1,2,3-triazoles, 1,2,4-triazoles, pyridines, pyrimidines) as potential bioisosteres. Investigations in [(35)S]GTPγS binding assays using membranes of Sf9 insect cells expressing the respective human histamine receptor subtype revealed only very weak activity of most of the synthesized hetarylalkylamines at both receptors. By contrast, the introduction of substituents at the 4-imidazolyl ring was most effective regarding H4R selectivity. This holds for methyl substitution in position 2 and, especially, in position 5. 5-Methylimbutamine (H4R: EC50 = 59 nM, α = 0.8) was equipotent with imbutamine at the hH4R, but revealed about 16-fold selectivity for the hH4R compared to the hH3R (EC50 980 nM, α = 0.36), whereas imbutamine preferred the hH3R. The functional activities were in agreement with radioligand binding data. The results support the hypothesis that, by analogy with histamine, methyl substitution in histamine homologs offers a way to shift the selectivity in favor of the H4R.

Absorptive chemistry based extraction for LC-MS/MS analysis of small molecule analytes from biological fluids - an application for 25-hydroxyvitamin D.

BACKGROUND: Already available sample preparation technologies for liquid chromatography-tandem mass spectrometry have substantial shortcomings with respect to automation. A novel approach is based on gel-like polymeric material with defined absorption chemistry, which is immobilized in micro-plate wells. It is referred to as Tecan Immobilized Coating Extraction™ (TICE™) technology and it enables easy automation on liquid handling systems. We aimed to study the performance of Tecan AC Extraction Plate™ based on this principle by addressing 25-hydroxyvitamin D (25OHD) as an exemplary analyte. METHODS: A protocol for extraction of 25OHD from serum samples based on TICE™ technology was implemented on a robotic liquid handling system Freedom EVO® (Tecan). An isotope-dilution ultra-performance liquid chromatography-tandem mass spectrometry method was used for quantification. Performance was tested according to a comprehensive protocol. RESULTS: Linearity was found over a range from 4.3 to 65.8 ng/mL for 25OHD3. The coefficients of variation for the intra-day and inter-day precision were <6% and accuracy ranged between 96.9% and 99.8% for 25OHD3. Recovery was 84% and efficient control of matrix effects was verified. High sample throughput could be observed with 96 samples prepared in <60 min. Close agreement of results was found for clinical samples analyzed with a second tandem mass spectrometry method based on protein precipitation and two-dimensional ultra-performance liquid chromatography for sample preparation (r=0.988, n=73). CONCLUSIONS: The new TICE™ technology was found to be a useful process for sample preparation in clinical mass spectrometry. Full automation suited for routine analysis was achieved.

Synthesis and pharmacological characterization of new tetrahydrofuran based compounds as conformationally constrained histamine receptor ligands.

A series of tetrahydrofuran based compounds with a bicyclic core that provides conformational restriction were synthesized and investigated by radioligand displacement studies and functional [(35)S]GTPγS binding assays at the human histamine receptor (hHR) subtypes. The amines and ((1S,3R,5S,6R)- and ((1S,3S,5S,6R)-3-(1H-imidazol-5-yl)-2-oxabicyclo[3.1.0]hexan-6-yl)methanamine), exhibited submicromolar Ki values at the hH3R with 10-fold higher affinities than their corresponding (6S)-epimers and 25- and >34-fold selectivity over the hH4R, respectively. Both compounds act as neutral antagonists at the hH3R with KB values of 181 and 32 nM, respectively. The cyanoguanidines of the imidazole series and the oxazole analogues turned out to be inactive at all hHR subtypes.

Spatially-explicit life cycle assessment of sun-to-wheels transportation pathways in the U.S.

Growth in biofuel production, which is meant to reduce greenhouse gas (GHG) emissions and fossil energy demand, is increasingly seen as a threat to food supply and natural habitats. Using photovoltaics (PV) to directly convert solar radiation into electricity for battery electric vehicles (BEVs) is an alternative to photosynthesis, which suffers from a very low energy conversion efficiency. Assessments need to be spatially explicit, since solar insolation and crop yields vary widely between locations. This paper therefore compares direct land use, life cycle GHG emissions and fossil fuel requirements of five different sun-to-wheels conversion pathways for every county in the contiguous U.S.: Ethanol from corn or switchgrass for internal combustion vehicles (ICVs), electricity from corn or switchgrass for BEVs, and PV electricity for BEVs. Even the most land-use efficient biomass-based pathway (i.e., switchgrass bioelectricity in U.S. counties with hypothetical crop yields of over 24 tonnes/ha) requires 29 times more land than the PV-based alternative in the same locations. PV BEV systems also have the lowest life cycle GHG emissions throughout the U.S. and the lowest fossil fuel inputs, except for locations with hypothetical switchgrass yields of 16 or more tonnes/ha. Including indirect land use effects further strengthens the case for PV.

A novel approach to signal normalisation in atmospheric pressure ionisation mass spectrometry.

The aim of our study was to test an alternative principle of signal normalisation in LC-MS/MS. During analyses, post column infusion of the target analyte is done via a T-piece, generating an "area under the analyte peak" (AUP). The ratio of peak area to AUP is assessed as assay response. Acceptable analytical performance of this principle was found for an exemplary analyte. Post-column infusion may allow normalisation of ion suppression not requiring any additional standard compound. This approach can be useful in situations where no appropriate compound is available for classical internal standardisation.

LC-MS method for screening unknown microbial carotenoids and isoprenoid quinones.

The structure of secondary metabolites from microorganisms provides a useful tool for microbial characterization and chemotaxonomic classification. Microbial isoprenoid quinones, for example, are well described and used to distinguish among photosynthetic microorganism groups. In addition, isoprenoid quinones can also be found, together with carotenoids, in non-photosynthetic microorganisms. The aim of the present study was to develop a LC-MS/MS method which can analyze and identify these microbial isoprenoids. Positive atmospheric pressure chemical ionization (APCI) together with collisionally induced dissociation was applied for generation of informative fragment spectra by mass spectrometry. Enhanced product ion (EPI) scan in a linear ion trap with information dependent data acquisition (IDA) enabled generation of MS fragment data even from minor isoprenoids. The developed liquid chromatography method enabled separation of isoprenoid patterns from their ester derivatives. Discovery and structural characterization of isoprenoid quinones and carotenoids were carried out by comparing characteristics of fragment spectra from unknown compounds with fragment spectra of a range of isoprenoid standard compounds and using published data. Throughout the study 17 microorganisms (e.g., Acremonium butyri, Arthrobacter spp., Brevibacterium linens, Bullera variabilis, Exophiala dermatitidis, Lecythophora hoffmannii, Panthoea agglomerans, Rhodotorula spp., Xanthophyllomyces dendrorhous) were screened and probable structures of isoprenoid quinones and carotenoids were suggested. The method lays some foundations on the analysis of yet unknown isoprenoids in microorganisms by using LCMS/MS techniques.

Synthesis and histamine H(3) and H(4) receptor activity of conformationally restricted cyanoguanidines related to UR-PI376.

Recently, we identified highly potent agonists of the human histamine H(4) receptor (hH(4) R) among a series of imidazolylbutylcyanoguanidines. Aiming at improved selectivity for the hH(4) R relative to the H(3) receptor (hH(3) R), the flexible tetramethylene linker connecting imidazole ring and cyanoguanidine group was replaced by conformationally restricted carbocycles. Introduction of a para- or a meta-phenylene spacer yielded only very weakly active compounds at both hH(3) R and hH(4) R (investigated in [(35) S]GTPγS binding assays using Sf9 insect cell membranes expressing hH(x) R subtypes). By contrast, the incorporation of a more flexible cyclohexane-1,4-diyl linker resulted in EC(50) or K(B) values ≥110 nM at hH(4) R and hH(3) R. Quality of action, potency and receptor subtype selectivity of the investigated compounds depend on the stereochemistry: Cis-configured diastereomers prefer the hH(4) R and are partial agonists, whereas trans-isomers are antagonists at the hH(4) R. At the hH(3) R the trans-diastereomers are superior to the cis-isomers by a factor of 10. The results on imidazolylcycloalkylcyanoguanidines suggest that variation of ring size and optimization of the stereochemistry may be useful to increase the potency and selectivity of hH(4) R agonists relative to the hH(3) R.

Resolution of natural microbial community dynamics by community fingerprinting, flow cytometry, and trend interpretation analysis.

Natural microbial communities generally have an unknown structure and composition because of their still not yet cultivable members. Therefore, understanding the relationships among the bacterial members, prediction of their behaviour, and controlling their functions are difficult and often only partly successful endeavours to date. This study aims to test a new idea that allows to follow community dynamics on the basis of a simple concept. Terminal restriction fragment length polymorphism (T-RFLP) analysis of bacterial 16S ribosomal RNA genes was used to describe a community profile that we define as composition of a community. Flow cytometry and analysis of DNA contents and forward scatter characteristics of the single cells were used to describe a community profile, which we define as structure of a community. Both approaches were brought together by a non-metric multidimensional scaling (n-MDS) for trend interpretation of changes in the complex community data sets. This was done on the basis of a graphical evaluation of the cytometric data, leading to the newly developed Dalmatian plot tool, which gave an unexpected insight into the dynamics of the unknown bacterial members of the investigated natural microbial community. The approach presented here was compared with other techniques described in the literature. The microbial community investigated in this study was obtained from a BTEX contaminated anoxic aquifer. The indigenous bacteria were allowed to colonise in situ microcosms consisting of activated carbon. These microcosms were amended with benzene and one of the electron acceptors nitrate, sulphate or ferric iron to stimulate microbial growth. The data obtained in this study indicated that the composition (via T-RFLP) and structure (via flow cytometry) of the natural bacterial community were influenced by the hydro-geochemical conditions in the test site, but also by the supplied electron acceptors, which led to distinct shifts in relative abundances of specific community members. It was concluded that engineered environments can be successfully monitored by single cell analytics in combination with established molecular tools and sophisticated statistical analyses, a combination that holds great promise for studying and monitoring natural microbial community behaviour.