Styrene-acrylonitrile-copolymer and acrylonitrile-butadiene-styrene-copolymer: a study on extractable and migratable oligomers.

Styrene-acrylonitrile-copolymer (SAN) and acrylonitrile-butadiene-styrene-copolymer (ABS) are gaining in importance as food contact materials. Oligomers and other non-intentionally added substances can migrate into foodstuffs. Five SAN and four ABS samples from the German market and manufacturers were extracted and the extractable oligomers were characterised by high performance liquid chromatography-mass spectrometry/ultraviolet detection/chemiluminescence nitrogen detection/fluorescence detection and gas chromatography-mass spectrometry. Trimers, formed from acrylonitrile and styrene units, were determined to be the dominating group of extractable oligomers in SAN and ABS in concentrations of about 4900-15800 mg/kg material. Furthermore, styrene-acrylonitrile dimers, styrene oligomers, styrene monomer and ethylbenzene were identified in the sample extracts. Migration testing with three consecutive migrations for multiple use articles was performed for two SAN articles. Migration of trimers into water, 3% acetic acid, 10% and 20% ethanol under hot-fill conditions (70°C, 2 h) was not detectable above 9 µg/dm2, while 50% ethanol acting as a food simulant for milk (124 µg/dm2 trimers during the third migration) was shown to overestimate the actual migration into milk (< 11 µg/dm2 trimers at 70°C, 2 h). 2-Amino-3-methyl-1-naphthalenecarbonitrile (AMNC), an oligomer degradation product and a primary aromatic amine, was detected in all material sample extracts (0.3-17.1 mg/kg material) and was released into food simulants in low amounts (< 0.014 µg/dm2 during the third migration into 50% ethanol at 70°C, 2 h).

Micro-fabricated packed metal gas preconcentrator for enhanced monitoring of ultralow concentration of isoprene.

A novel non-silicon-based micro-preconcentration device, as a pretreatment component in a portable gas chromatography system, was developed for the preconcentration one of the trace volatile organic compounds (VOCs) in the exhaled gases, which is one typical biomarker for the chronic liver disease (CLD). The device was designed as an array of manifold-shaped rectangular metal micro-channels with flat dimensions of 16 mm × 12.6 mm and the internal empty volume is 14.4 µL on the copper substrate. Instead of the non-silicon fabrication process, the traditional laser etching technology (LET) was optimized to etch micro-channels, and vacuum diffusion welding (VDW) was applied to form internal channels. The fabricated chip was filled with Carbopack X adsorbent. In the testing, the metal gas preconcentrator (MGP) was installed in a commercial GC (gas chromatography) and nitrogen was used as carrier gas and desorbed gas. With the MPG, up to 352 of concentration factor can be achieved for 10 ppb isoprene. The developed MGP, which has advantages of high strength, low cost, good thermal conductivities, can potentially be used for non-invasive screening of advanced liver fibrosis by monitoring isoprene concentrations in exhaled breath.

Controlling guest conformation for efficient purification of butadiene.

Conventional adsorbents preferentially adsorb the small, high-polarity, and unsaturated 1,3-butadiene molecule over the other C4 hydrocarbons from which it must be separated. We show from single-crystal x-ray diffraction and computational simulation that a hydrophilic metal-organic framework, [Zn2(btm)2], where H2btm is bis(5-methyl-1H-1,2,4-triazol-3-yl)methane, has quasi-discrete pores that can induce conformational changes in the flexible guest molecules, weakening 1,3-butadiene adsorption through a large bending energy penalty. In a breakthrough operation at ambient temperature and pressure, this guest conformation-controlling adsorbent eluted 1,3-butadiene first, then butane, butene, and isobutene. Thus, 1,3-butadiene can be efficiently purified (≥99.5%) while avoiding high-temperature conditions that can lead to its undesirable polymerization.

Isoprenoids Production from Lipid-Extracted Microalgal Biomass Residues Using Engineered E. coli.

Microalgae are recognized as a third generation feedstock for biofuel production due to their rapid growth rates and lignin-free characteristics. In this study, a lipid extracted microalgal biomass residues was used as the raw material to produce isoprene, α-pinene and ß-pinene with an engineered E. coli strain. We adopted an optimal sulfuric acid hydrolysis method (1:7 ratio of solid to acid solution, 32% (w/v) concentration of sulfuric acid solution at 90 °C for 90 min) to efficiently convert holocellulose into glucose efficiently (6.37 g/L). Futhermore, we explored a novel detoxification strategy (phosphoric acid/calcium hydroxide) to remove inhibitors and notably acetic acid, furfural and 5-hydroxymethylfurfural (5-HMF) were reduced by 5.32%, different number given later 99.19% and 98.22%, respectively. Finally, the fermentation concentrations of isoprene (223.23 mg/L), α-pinene (382.21 µg/L) and ß-pinene (17.4 mg/L) were achieved using the detoxified hydrolysate as the carbon source, equivalent to approximately 86.02%, 90.16% and 88.32% of those produced by the engineered E. coli strain fermented on pure glucose, respectively.

Identification of bacteria using volatile organic compounds.

The rapid diagnosis of respiratory infections has always been an important goal for medical professionals, because rapid and accurate diagnosis leads to proper and timely treatment, and consequently, reduces the costs of incorrect and long-term treatments, and antibiotic resistance. The present study was conducted with the aim of detecting volatile organic compounds (VOCs) in three bacteria: Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae. Headspace of the studied bacteria, after separately culturing in two types of liquid medium in three different time-periods, was extracted by solid phase microextraction and analysed by gas chromatography mass spectrometry The analysis results of the VOCs produced by the studied bacteria indicate that some VOCs are common and some are unique in each bacterium. 1-penten-3-ol, levomenthol, and 2-octyl-1-ol for P. aeruginosa, cyclohexene, 4-ethenyl, and cis-Dihydro-α-terpinyl acetate for A. baumannii and 1,3-butadiene, butyraldehyde, longifolene, octyl acetate, tridecanol, dodecenal, (E)-2-hexyl ester, butanoic acid, and 5,5-dodecadinyl-1 12-diol for K. pneumoniae were identified as unique VOCs for each bacterium. Finally, it can be said that an accurate and rapid bacterial detection method can be achieved by using a tool that can detect bacterial VOCs. However, more studies are needed to design a tool for which all aspects have been assessed, so that it can give us a more complete pattern for the use of these compounds as biomarkers.

Combining Gal4p-mediated expression enhancement and directed evolution of isoprene synthase to improve isoprene production in Saccharomyces cerevisiae.

Current studies on microbial isoprene biosynthesis have mostly focused on regulation of the upstream mevalonic acid (MVA) or methyl-erythritol-4-phosphate (MEP) pathway. However, the downstream bottleneck restricting isoprene biosynthesis capacity caused by the weak expression and low activity of plant isoprene synthase (ISPS) under microbial fermentation conditions remains to be alleviated. Here, based on a previously constructed Saccharomyces cerevisiae strain with enhanced precursor supply, we strengthened the downstream pathway through increasing both the expression and activity of ISPS to further improve isoprene production. Firstly, a two-level expression enhancement system was developed for the PGAL1-controlled ISPS by overexpression of GAL 4. Meanwhile, the native GAL1/7/10 promoters were deleted to avoid competition for the transcriptional activator Gal4p, and GAL80 was disrupted to eliminate the dependency of gene expression on galactose induction. The IspS expression was obviously elevated upon enhanced Gal4p supply, and the isoprene production was improved from 6.0mg/L to 23.6mg/L in sealed-vial cultures with sucrose as carbon source. Subsequently, a novel high-throughput screening method was developed based on precursor toxicity and used for ISPS directed evolution towards enhanced catalytic activity. Combinatorial mutagenesis of the resulting ISPS mutants generated the best mutant ISPSM4, introduction of which into the GAL4-overexpressing strain YXM29 achieved 50.2mg/L of isoprene in sealed vials, and the isoprene production reached 640mg/L and 3.7g/L in aerobic batch and fed-batch fermentations, respectively. These results demonstrated the effectiveness of the proposed combinatorial engineering strategy in isoprene biosynthesis, which might also be feasible and instructive for biotechnological production of other valuable chemicals.

Synergy between methylerythritol phosphate pathway and mevalonate pathway for isoprene production in Escherichia coli.

Isoprene, a key building block of synthetic rubber, is currently produced entirely from petrochemical sources. In this work, we engineered both the methylerythritol phosphate (MEP) pathway and the mevalonate (MVA) pathway for isoprene production in E. coli. The synergy between the MEP pathway and the MVA pathway was demonstrated by the production experiment, in which overexpression of both pathways improved the isoprene yield about 20-fold and 3-fold, respectively, compared to overexpression of the MEP pathway or the MVA pathway alone. The (13)C metabolic flux analysis revealed that simultaneous utilization of the two pathways resulted in a 4.8-fold increase in the MEP pathway flux and a 1.5-fold increase in the MVA pathway flux. The synergy of the dual pathway was further verified by quantifying intracellular flux responses of the MEP pathway and the MVA pathway to fosmidomycin treatment and mevalonate supplementation. Our results strongly suggest that coupling of the complementary reducing equivalent demand and ATP requirement plays an important role in the synergy of the dual pathway. Fed-batch cultivation of the engineered strain overexpressing the dual pathway resulted in production of 24.0g/L isoprene with a yield of 0.267g/g of glucose. The synergy of the MEP pathway and the MVA pathway also successfully increased the lycopene productivity in E. coli, which demonstrates that it can be used to improve the production of a broad range of terpenoids in microorganisms.

Aß-42 lowering agents from the marine-derived fungus Dichotomomyces cejpii.

The ascomycete Dichotomomyces cejpii was isolated from the marine sponge Callyspongia cf. C. flammea. Three new steroids (1-3), two of which are present as glycosides, with an untypical pattern of carbon-carbon double bounds, were obtained from fungal extracts, as well as the known xanthocillin X dimethyl ether (4). Compounds 2 and 4 were evaluated in an Alzheimer's disease cellular assay and found capable of preventing the enhanced production of amyloid ß-42 in Aftin-5 treated cells. Aß-42 lowering agents are considered as candidates for the treatment of neurodegenerative Alzheimer's disease.

Separation of linear synthetic polymers in non-aqueous capillary zone electrophoresis using cationic surfactant.

A method for separating water-insoluble and neutral synthetic polymers using non-aqueous capillary zone electrophoresis (NACZE) was developed. The non-aqueous solvent system comprising a mixture of tetrahydrofuran, acetonitrile, and ethanol containing cetyltrimethylammonium chloride was used for solubilizing and conferring positive charges to the polymers. A mixture of polystyrene (PS, Mn=6500) and polybutadiene (PBD, Mn=5900) was successfully separated by the NACZE method using cationic surfactants. Evaluation of the effect of the molecular weight of the polymers on the electrophoretic behavior demonstrated that PSs with different molecular weights (Mn=6500, 10,200, 19,600, 200,000) were co-eluted as a single peak. That is, the apparent electrophoretic mobility of the PSs was independent of the molecular weight. In contrast, evaluation of PBD and polycarbonate (PC) demonstrated that the solubility of polymers in the medium affected the apparent electrophoretic mobility of the polymers, where low solubility resulted in reduced apparent electrophoretic mobility. Using the proposed method, poly(styrene-co-methylmethacrylate)s with different compositions were successfully separated.

Co-recycling of acrylonitrile-butadiene-styrene waste plastic and nonmetal particles from waste printed circuit boards to manufacture reproduction composites.

This study investigated the feasibility of using acrylonitrile-butadiene-styrene (ABS) waste plastic and nonmetal particles from waste printed circuit boards (WPCB) to manufacture reproduction composites (RC), with the aim of co-recycling these two waste resources. The composites were prepared in a twin-crew extruder and investigated by means of mechanical testing, in situ flexural observation, thermogravimatric analysis, and dimensional stability evaluation. The results showed that the presence of nonmetal particles significantly improved the mechanical properties and the physical performance of the RC. A loading of 30 wt% nonmetal particles could achieve a flexural strength of 72.6 MPa, a flexural modulus of 3.57 GPa, and an impact strength of 15.5 kJ/m2. Moreover, it was found that the application of maleic anhydride-grafted ABS as compatilizer could effectively promote the interfacial adhesion between the ABS plastic and the nonmetal particles. This research provides a novel method to reuse waste ABS and WPCB nonmetals for manufacturing high value-added product, which represents a promising way for waste recycling and resolving the environmental problem.

Multidetector thermal field-flow fractionation as a novel tool for the microstructure separation of polyisoprene and polybutadiene.

For the first time, it is demonstrated that thermal field-flow fractionation (ThFFF) is an efficient tool for the fractionation of polyisoprene (PI) and polybutadiene (PB) with regard to molecular microstructure. ThFFF analysis of 1,4- and 3,4-PI as well as 1,4- and 1,2-PB samples in tetrahydrofuran (THF), THF/cyclohexane, and cyclohexane reveals that isomers of the same polymer family having similar molar masses exhibit different Soret coefficients depending on microstructure for each solvent. The separation according to microstructure is found to be based on the cooperative influence of the normal and the thermal diffusion coefficient. Of the three solvents, cyclohexane has the greatest influence on the fractionation of the isomers. In order to determine the distribution of isomeric structures in the PI and PB samples, the samples are fractionated by ThFFF in cyclohexane and subsequently analyzed by (1) H NMR. The isomeric distributions determined from NMR data correlate well with ThFFF retention data of the samples and thus further highlight the unique fractionating capabilities of ThFFF. The interplay of the normal and thermal diffusion coefficients that are influenced by temperature and the mobile phase opens the way to highly selective fractionations without the drawbacks of column-based separation methods.

Gas-phase advanced oxidation for effective, efficient in situ control of pollution.

In this article, gas-phase advanced oxidation, a new method for pollution control building on the photo-oxidation and particle formation chemistry occurring in the atmosphere, is introduced and characterized. The process uses ozone and UV-C light to produce in situ radicals to oxidize pollution, generating particles that are removed by a filter; ozone is removed using a MnO2 honeycomb catalyst. This combination of in situ processes removes a wide range of pollutants with a comparatively low specific energy input. Two proof-of-concept devices were built to test and optimize the process. The laboratory prototype was built of standard ventilation duct and could treat up to 850 m(3)/h. A portable continuous-flow prototype built in an aluminum flight case was able to treat 46 m(3)/h. Removal efficiencies of >95% were observed for propane, cyclohexane, benzene, isoprene, aerosol particle mass, and ozone for concentrations in the range of 0.4-6 ppm and exposure times up to 0.5 min. The laboratory prototype generated a OH(•) concentration derived from propane reaction of (2.5 ± 0.3) × 10(10) cm(-3) at a specific energy input of 3 kJ/m(3), and the portable device generated (4.6 ± 0.4) × 10(9) cm(-3) at 10 kJ/m(3). Based on these results, in situ gas-phase advanced oxidation is a viable control strategy for most volatile organic compounds, specifically those with a OH(•) reaction rate higher than ca. 5 × 10(-13) cm(3)/s. Gas-phase advanced oxidation is able to remove compounds that react with OH and to control ozone and total particulate mass. Secondary pollution including formaldehyde and ultrafine particles might be generated, depending on the composition of the primary pollution.

Full method validation for the determination of hexachlorobenzene and hexachlorobutadiene in fish tissue by GC-IDMS.

This paper summarizes the validation strategy and the results obtained for the simultaneous determination of hexachlorobenzene (HCB) and hexachlorobutadiene (HCBD) in fish tissue with a maximum of about 10% m/m fat content using a GC-IDMS technique. The method is applicable for the determination of HCB and HCBD at trace levels in different kinds of fish tissue samples in accordance with the requirements of the EU Directive 2008/105/EC establishing Environmental Quality Standard (EQS) levels for biota in aquatic ecosystems (10 ng/g for HCB and 55 ng/g for HCBD). The method validation aimed to assess performance parameters such as linearity, limit of detection/limit of quantification (LOD/LOQ), trueness, selectivity, intermediate precision, repeatability, stability of the extracts and robustness. The validation experiments have been performed by using uncontaminated fish tissue. Trueness was evaluated by using a certified reference material (NIST SRM 1947) (where applicable) and by the standard addition method. Very good linear signal-concentration curves were obtained for both analytes over the whole range of calibration. The repeatability and the intermediate precision of the method, expressed as relative standard deviation (RSD) and calculated at the EQS level, were estimated to be below 3% both for HCB and HCBD. The limits of quantification were 3.7 ng/g for HCB and 15.7 ng/g for HCBD in the fish. An uncertainty budget for the measurement of both HCB and HCBD in fish at about the EQS levels, applying the described method, has been established in the order of 10%. The analytical method and its performance characteristics take into account the requirements of EU Directive 2009/90/EC regarding the establishment of minimum performance criteria for the methods of analysis to be used in the water monitoring activity of the Water Framework Directive. Finally, the validated method was successfully tested on contaminated Silurus glanis from Ebro River (Spain). The method will be used in the homogeneity, stability and interlaboratory comparison studies for the characterization of a new candidate certified reference material.

Comprehensive triblock copolymer analysis by coupled thermal field-flow fractionation-NMR.

Thermal field-flow fractionation (ThFFF) is used as a novel fractionation technique to investigate the molecular heterogeneity of PB-b-PVP-b-PtBMA triblock copolymers. Such copolymers cause major problems in liquid chromatography due to very strong polar interactions with the stationary phase. ThFFF separates the copolymers with regard to size and/or chemical composition based on the normal and thermal diffusion coefficients. The separation mechanism in ThFFF and the chemical composition of the separated species is elucidated by online (1) H NMR. Based on the compositional analysis and a calibration of the system with the respective homopolymers, the samples are quantified regarding their molar masses, chemical compositions, and microstructures providing comprehensive information on the complex structure of these block copolymers.

SD118-xanthocillin X (1), a novel marine agent extracted from Penicillium commune, induces autophagy through the inhibition of the MEK/ERK pathway.

A compound named SD118-xanthocillin X (1) (C(18)H(12)N(2)O(2)), isolated from Penicillium commune in a deep-sea sediment sample, has been shown to inhibit the growth of several cancer cell lines in vitro. In the present study, we employed a growth inhibition assay and apoptotic analysis to identify the biological effect and detailed mechanism of SD118-xanthocillin X (1) in human hepatocellular carcinoma (HepG2) cells. SD118-xanthocillin X (1) demonstrated a concentration-dependent inhibitory effect on the growth of HepG2 cells and caused slight cellular apoptosis and significantly induced autophagy. Autophagy was detected as early as 12 h by the conversion of microtubule-associated protein 1 light chain 3 (LC3-I) to LC3-II, following cleavage and lipid addition to LC3-I. The pharmacological autophagy inhibitor 3-methyladenine largely attenuates the growth inhibition and autophagic effect of SD118-xanthocillin X (1) in HepG2 cells. Our data also indicated that the autophagic effect of SD118-xanthocillin X (1) occurs via the down-regulation of the MEK/ERK signaling pathway and the up-regulated class III PI3K/Beclin 1 signaling pathway.

Ultrasonic degradation of butadiene, styrene and their copolymers.

Ultrasonic degradation of commercially important polymers, styrene-butadiene (SBR) rubber, acrylonitrile-butadiene (NBR) rubber, styrene-acrylonitrile (SAN), polybutadiene rubber and polystyrene were investigated. The molecular weight distributions were measured using gel permeation chromatography (GPC). A model based on continuous distribution kinetics approach was used to study the time evolution of molecular weight distribution for these polymers during degradation. The effect of solvent properties and ultrasound intensity on the degradation of SBR rubber was investigated using different pure solvents and mixed solvents of varying volatility and different ultrasonic intensities.

Bio-isoprene production using exogenous MVA pathway and isoprene synthase in Escherichia coli.

In this paper, an original strategy is employed to biosynthesize the isoprene by heterologously co-expressing the Saccharomyces cerevisiae MVA pathway and isoprene synthase (IspS) from Populus alba in the Escherichia coli BL21 (DE3) strain, which was screened from three different IspS enzymes. The finally genetic strain YJM13 harboring the MVA pathway and ispS(Pa) gene could accumulate isoprene up to 2.48 mg/l and 532 mg/l under the flask and fed-batch fermentation conditions, respectively, which is about three times and five times to the control strain. The result proves to be higher than that in the report documents. In this way, a potential production system for isoprene from renewable sources via the MVA pathway in E. coli has been provided.

Induced production of N-formyl alkaloids from Aspergillus fumigatus by co-culture with Streptomyces peucetius.

Co-culture of the fungus Aspergillus fumigatus with the bacteria Streptomyces peucetius led to the induction of production of formyl xanthocillin analogues. This mixed fermentation yielded two new metabolites, fumiformamide (1) and N,N'-((1Z,3Z)-1,4-bis(4-methoxyphenyl)buta-1,3-diene-2,3-diyl)diformamide (2), together with two known N-formyl derivatives and the xanthocillin analogue BU-4704. The structures were determined by spectroscopic methods and by comparison with literature. Cytotoxic activity of all the analogues was tested on the NCI-60 cell line screen, and compound 2 exhibited significant activity against several cell lines. The analogues did not show antimicrobial activity.

Dynamic profiles of volatile organic compounds in exhaled breath as determined by a coupled PTR-MS/GC-MS study.

In this phenomenological study we focus on dynamic measurements of volatile organic compounds (VOCs) in exhaled breath under exercise conditions. An experimental setup efficiently combining breath-by-breath analyses using proton transfer reaction mass spectrometry (PTR-MS) with data reflecting the behaviour of major hemodynamic and respiratory parameters is presented. Furthermore, a methodology for complementing continuous VOC profiles obtained by PTR-MS with simultaneous SPME/GC-MS measurements is outlined. These investigations aim at evaluating the impact of breathing patterns, cardiac output or blood pressure on the observed breath concentration and allow for the detection and identification of several VOCs revealing characteristic rest-to-work transitions in response to variations in ventilation or perfusion. Examples of such compounds include isoprene, methyl acetate, butane, DMS and 2-pentanone. In particular, both isoprene and methyl acetate exhibit a drastic rise in concentration shortly after the onset of exercise, usually by a factor of about 3-5 within approximately 1 min of pedalling. These specific VOCs might also be interpreted as potentially sensitive indicators for fluctuations of blood or respiratory flow and can therefore be viewed as candidate compounds for future assessments of hemodynamics, pulmonary function and gas exchange patterns via observed VOC behaviour.

Establishment of new crops for the production of natural rubber.

Natural rubber is a unique biopolymer of strategic importance that, in many of its most significant applications, cannot be replaced by synthetic alternatives. The rubber tree Hevea brasiliensis is the almost exclusive commercial source of natural rubber currently and alternative crops should be developed for several reasons, including: a disease risk to the rubber tree that could potentially decimate current production, a predicted shortage of natural rubber supply, increasing allergic reactions to rubber obtained from the Brazilian rubber tree and a general shift towards renewables. This review summarizes our knowledge of plants that can serve as alternative sources of natural rubber, of rubber biosynthesis and the scientific gaps that must be filled to bring the alternative crops into production.