Conversion of polyhydroxybutyrate (PHB) to methyl crotonate for the production of biobased monomers

Within the concept of the replacement of fossil with biobased resources, bacterial polyhydroxybutyrate (PHB) can be obtained from volatile fatty acids (VFAs) from agro‐food waste streams and used as an intermediate toward attractive chemicals. Here we address a crucial step in this process, the conversion of PHB to methyl crotonate (MC), which can be converted via cross‐metathesis with ethylene to methyl acrylate and propylene, two important monomers for the plastics industry. The conversion of PHB to MC proceeds via a thermolysis of PHB to crotonic acid (CA), followed by an esterification to MC. At pressures below 18 bar, the thermolysis of PHB to CA is the rate‐determining step, where above 18 bar, the esterification of CA to MC becomes rate limiting. At 200°C and 18 bar, a full conversion and 60% selectivity to MC is obtained. This conversion circumvents processing and application issues of PHB as a polymer and allows PHB to be used as an intermediate to produce biobased chemicals. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42462.     

Climate driven release of carbon and mercury from permafrost mires increases mercury loading to sub-arctic lakes

In sub-arctic and arctic regions mercury is an element of concern for both wildlife and humans. Over thousands of years large amounts of atmospherically deposited mercury, both from natural and anthropogenic sources, have been sequestered together with carbon in northern peatlands. Many of these peatlands are currently underlain by permafrost, which controls mire stability and hydrology. With the ongoing climate change there is concern that permafrost thawing will turn large areas of these northern peatlands from carbon/mercury-sinks into much wetter carbon/mercury-sources. Here we can show that such a change in mire structure in the sub-arctic Stordalen mire in northern Sweden actually is responsible for an increased export of mercury to the adjacent lake Inre Harrsjön. We also show that sediment mercury accumulation rates during a warm period in the pre-industrial past were higher than in the 1970s when atmospheric input peaked, indicating that in areas with permafrost, climate can have an effect on mercury loading to lakes as large as anthropogenic emissions. Thawing of permafrost and the subsequent export of carbon is a widespread phenomenon, and the projection is that it will increase even more in the near future. Together with our observations from Stordalen, this makes northern peatlands into a substantial source of mercury, at risk of being released into sensitive arctic freshwater and marine systems.     

Modelling of transient kinetics in catalytic three-phase reactors: Enantioselective hydrogenation

Transient techniques are frequently used for catalytic gas-phase processes, but the application of transient techniques on catalytic three-phase systems is very scarce. Transient kinetic experiments provide valuable additional information about the behaviour of complex organic reaction systems, which was illustrated here with continuous enantioselective three-phase hydrogenation of ethyl benzoylformate over supported Pt catalyst particles in a fixed bed. The catalyst stability and the details of the adsorption–desorption behaviour of the reaction participants were revealed by transient experiments. Quantitative modelling of the data was based on kinetic experiments and characterisation of the reactor flow pattern by an inert tracer. Both liquid-phase species and adsorbed surface species were included in the modelling. The model predicted correctly the dynamic behaviour of the complex organic system under transient conditions. The approach is generally applicable to complex organic systems undergoing catalytic transformations.     

Crystal Structure of the Human Monoacylglycerol Lipase,a Key Actor in Endocannabinoid Signaling

2‐Arachidonoylglycerol plays a major role in endocannabinoid signaling, and is tightly regulated by the monoacylglycerol lipase (MAGL). Here we report the crystal structure of human MAGL. The protein crystallizes as a dimer, and despite structural homologies to haloperoxidases and esterases, it distinguishes itself by a wide and hydrophobic access to the catalytic site. An apolar helix covering the active site also gives structural insight into the amphitropic character of MAGL, and likely explains how MAGL interacts with membranes to recruit its substrate. Docking of 2‐arachidonoylglycerol highlights a hydrophobic and a hydrophilic cavity that accommodate the lipid into the catalytic site. Moreover, we identified Cys201 as the crucial residue in MAGL inhibition by N‐arachidonylmaleimide, a sulfhydryl‐reactive compound. Beside the advance in the knowledge of endocannabinoids degradation routes, the structure of MAGL paves the way for future medicinal chemistry works aimed at the design of new drugs exploiting 2‐arachidonoylglycerol transmission.     

Carbonation of calcium-containing mineral and industrial by-products

The use of carbon dioxide (CO₂) and calcium-containing by-products from industrial activities is receiving increasing interest as a route to valuable carbonate materials while reducing CO₂ emissions and saving natural resources. In this work, wet-chemical experimental data was assessed, which involved the carbonation of three types of materials in aqueous solutions, namely, 1) wollastonite, a calcium silicate mineral, 2) steelmaking slag, a by-product of steel production, and 3) paper bottom ash (PBA) from waste paper incineration. Aims were to achieve either a high carbonation degree and/or a pure carbonate product with potential commercial value. Producing a pure precipitated calcium carbonate (PCC) material that may find use in paper industry products puts strong requirements on purity and brightness. The parameters investigated were particle size, CO₂ pressure, temperature, solid/liquid ratio, and the use of additives that affect the solubilities of CO₂ and/or calcium carbonate. Temperatures and pressures were varied up to 180°C and 4 MPa. Data obtained with the wollastinite mineral allowed for a comparison between natural resources and the industrial by-product materials, the latter typically being more reactive. With respect to temperature and pressure trends reported by others were largely confirmed, with temperatures above 150°C introducing thermodynamic limitations depending on CO₂ pressure. The influence of additives showed some promise, although costs may make recycling and reuse of additives a necessity for a large-scale process. When using steelmaking slag, magnetic separation may remove some iron-containing material from the process (although this is far from perfect), while the addition of bicarbonate supported the removal of phosphorous, aside from improving calcium extraction. The experiments with paper bottom ash (PBA) gave new data, showing that its reactivity resembles that of steelmaking slag, while its composition results in relatively pure carbonate product. Also, with PBA no additives were needed to achieve this.     

Mineralogy of air-pollution-control residues from a secondary lead smelter: environmental implications

The mineralogy and solubility of air-pollution-control (APC) residues from a secondary lead (Pb) smelter have been studied on samples from the Príbram smelter, Czech Republic, recycling car batteries, with the emphasis on their potential environmental effect. The presence of dominant anglesite (PbSO4) and laurionite (Pb(OH)Cl) was observed in a sintered residue from after-burning chambers (800-1000 degrees C). In contrast, low-temperature Pb-bearing phases, such as KCl x 2PbCl2 and caracolite (Na3Pb2(SO4)3Cl), were detected in the major APC residue from bag-type fabric filters. Metallic elements, zinc (Zn), cadmium (Cd), and tin (Sn) were found homogeneously distributed within this residue. The formation of anglesite, cotunnite (PbCl2), (Zn,Cd)2SnO4, and (Sb,As)2O3 was observed during the sintering of this APC residue at 500 degrees C in a rotary furnace. The 168 h leaching test on filter residue, representing the fraction that may escape the flue gas treatment system, indicated rapid release of Pb and other contaminants. Caracolite and KCl x 2PbCl2 are significantly dissolved, and anglesite and cotunnite form the alteration products, as was confirmed by mineralogical analysis and PHREEQC-2 modeling. The observed Pb-bearing chlorides have significantly higher solubility than anglesite and, following emission from the smelter stack, can readily dissolve, transferring Pb into the environmental milieu (soils, water, inhabited areas).     

Computer aided boar semen motility analysis for cereulide detection in different food matrices

Computer Aided Semen Analysis (CASA) study of the boar semen motility has been demonstrated to be an appropriate assay for detection of cereulide (Bacillus cereus emetic toxin). Application of the boar semen bio-assay to detect cereulide directly in foods requires investigation of potential interference of food components, preservatives and other microbial and chemical food contaminants with the bio-assay. Current study provides evidence that none of included Staphylococcus aureus enterotoxins A, B, C and D nor B. cereus Hemolysin BL (HBL) and non-hemolytic enterotoxin (NHE) and three mycotoxins (Sterigmatocystin, Fumonisin B1 and Patulin) exhibited a toxic impact on semen progressive motility. Aflatoxin M1, M3 and zearalenone impaired semen motility only at concentrations (0.004 mg ml(-1), 0.1 mg ml(-1) and 10 mg ml(-1), respectively) much higher than those found in foods and those permitted by legislation, in comparison to cereulide which induces motility cease at concentrations lower than 20 ng ml(-1). Ten commonly used preservatives, namely potassium sorbate, sodium benzoate, (DL) malic acid, citric acid, (L+) tartaric acid, acetic acid, (DL) lactic acid, (L+) ascorbic acid, sodium chloride and sucrose induced no cease in spermatozoa motility even at preservative concentrations higher than permitted by legislation. Dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and acrylamide had no acute effect on spermatozoa motility at concentrations of 500 and 10,000 mg ml(-1), respectively. Robustness of computer aided boar semen motility analysis, tested with 14 different foods inoculated with cereulide producing B. cereus, showed distinct cereulide production in seven samples (although B. cereus growth to counts higher than 8 log CFU g(-1) was noted in 11 samples), in amounts close to those reported in foodborne outbreaks. Test evaluation in 33 samples suspected to hold cereulide showed actual cereulide presence in ten samples and no interference of food matrix with the assay.     

Spectral quality of photo-selective shade nettings improves antioxidants and overall quality in selected fresh produce after postharvest storage

Growing vegetables under shade nets is currently becoming popular in summer to provide protection from high intensities of light. High temperatures and light quality affect postharvest quality and storage life of vegetables. Photo-selective shade netting technology is an emerging agro-technological concept that aims at the improvement of crop quality by the modification of spectral light and provides physical protection of the crop. Incorporation of various light-dispersive and reflective chromatic additives in the photo-selective nets is responsible for the modification of spectral quality, especially in the UV 200–400 nm, visible (400–700 nm), or far-red (FR; also known as “near infrared”; 705–740 nm) in the infrared region of the spectral region. Altered light-quality changes under the photo-selective nets were shown to improve the accumulation of phytochemicals and aroma compounds, and ultimately, the growth, yield, and quality of the selected vegetables such as tomatoes, sweet peppers, lettuce, and aromatic herbs. The postharvest quality of fresh produce is also influenced by environmental conditions such as light, average temperature, minimum temperature, and day-night temperature differences. During production, light quality under the photo-selective shade nets had a positive effect on the quality parameters and phytochemical content in fresh produce after postharvest storage.

The review includes the use of photo-selective netting in protected agriculture as a preharvest tool to improve aroma volatiles, antioxidants, and overall quality of fresh produce after postharvest storage.