Rapid and effective decontamination of chlorophenol-contaminated soil by sorption into commercial polymers: concept demonstration and process modeling.

Solid phase extraction performed with commercial polymer beads to treat soil contaminated by chlorophenols (4-chlorophenol, 2,4-dichlorophenol and pentachlorophenol) as single compounds and in a mixture has been investigated in this study. Soil-water-polymer partition tests were conducted to determine the relative affinities of single compounds in soil-water and polymer-water pairs. Subsequent soil extraction tests were performed with Hytrel 8206, the polymer showing the highest affinity for the tested chlorophenols. Factors that were examined were polymer type, moisture content, and contamination level. Increased moisture content (up to 100%) improved the extraction efficiency for all three compounds. Extraction tests at this upper level of moisture content showed removal efficiencies ≥70% for all the compounds and their ternary mixture, for 24 h of contact time, which is in contrast to the weeks and months, normally required for conventional ex situ remediation processes. A dynamic model characterizing the rate and extent of decontamination was also formulated, calibrated and validated with the experimental data. The proposed model, based on the simplified approach of "lumped parameters" for the mass transfer coefficients, provided very good predictions of the experimental data for the absorptive removal of contaminants from soil at different individual solute levels. Parameters evaluated from calibration by fitting of single compound data, have been successfully applied to predict mixture data, with differences between experimental and predicted data in all cases being ≤3%.

Production of polyhydroxybutyrate by the cyanobacterium cf. Anabaena sp.

Polyhydroxybutyrate (PHB) production by the cyanobacterium cf. Anabaena sp. was here studied by varying the medium composition and the carbon source used to induce mixotrophic growth conditions. The highest PHB productivity (0.06 gPHB gbiomass-1 d-1) was observed when cultivating cf. Anabaena sp. in phosphorus-free medium and in the presence of sodium acetate (5.0 g L-1 concentration), after an incubation period of 7 days. A content of 40% of PHB on biomass, a dry weight of 0.1 g L-1, and a photosynthetic efficiency equal to the control were obtained. The cyanobacterium was then grown on a larger scale (10 L) to evaluate the characteristics of the produced PHB in relation to the main composition of the biomass (the content of proteins, polysaccharides, and lipids): after an incubation period of 7 days, a content of 6% of lipids (52% of which as unsaturated fatty acids with 18 carbon atoms), 12% of polysaccharides, 28% of proteins, and 46% of PHB was reached. The extracted PHB had a molecular weight of 3 MDa and a PDI of 1.7. These promising results demonstrated that cf. Anabaena sp. can be included among the Cyanobacteria species able to produce polyhydroxyalkanoates (PHAs) either in photoautotrophic or mixotrophic conditions, especially when it is grown under phosphorus-free conditions.

Disposable electrochemical sensor combined with molecularly imprinted solid-phase extraction for catabolites detection of flavan-3-ol in urine samples.

Polyphenols are bioactive substances of vegetal origin with a significant impact on human health. The assessment of polyphenol intake and excretion is therefore important. In this work, a new electrochemical approach based on molecularly imprinted polymer extraction and preconcentration, combined with a disposable carbon screen-printed sensor and adsorptive transfer differential pulse voltammetry detection has been proposed for quantifying of 4-hydroxyphenylacetic acid (4-HPA), which is a biomarker of flavan-3-ols intake, and other phenolic acids. The simple experimental performance has allowed the rapid data collection with relevant information about the profile of catabolites extracted. The method was validated over a concentration range of 10-200 mg L-1, R2 > 0.999. In the optimized conditions, the recovery value was 94% with RSD 8%. The limits of detection and quantification were 2.38 mg L-1 and 7.21 mg L-1, respectively. The method was validated by means of a chromatographic method, being the differences between the values of the 4-HPA concentrations obtained by both methods under 1%. The proposed method showed high recoveries, low detection limit, and good accuracy, providing a fast, reliable, and cheap procedure to quantify phenolic metabolites in urine, and representing therefore a good and interesting alternative method. Also, the procedure offers other advantages, including the miniaturization, the low use of organic solvents, the ability to analyse small volumes of samples, in situ analysis and simple instrumentation requirement.

Enhanced production of poly(3-hydroxybutyrate) in recombinant Escherichia coli and EDTA-microwave-assisted cell lysis for polymer recovery.

Poly(3-hydroxybutyrate) (PHB) is a bacterial polymer of great commercial importance due to its properties similar to polypropylene. With an aim to develop a recombinant system for economical polymer production, PHB biosynthesis genes from Bacillus aryabhattai PHB10 were cloned in E. coli. The recombinant cells accumulated a maximum level of 6.22 g/L biopolymer utilizing glycerol in shake flasks. The extracted polymer was confirmed as PHB by GC-MS and NMR analyses. The polymer showed melting point at 171 °C, thermal stability in a temperature range of 0-140 °C and no weight loss up to 200 °C. PHB extracted from sodium hypochlorite lysed cells had average molecular weight of 143.108 kDa, polydispersity index (PDI) 1.81, tensile strength of 14.2 MPa and an elongation at break of 7.65%. This is the first report on high level polymer accumulation in recombinant E. coli solely expressing PHB biosynthesis genes from a Bacillus sp. As an alternative to sodium hypochlorite cell lysis mediated polymer extraction, the effect of combined treatment with ethylenediaminetetraacetic acid and microwave was studied which attained 93.75% yield. The polymer recovered through this method was 97.21% pure, showed 2.9-fold improvement in molecular weight and better PDI. The procedure is simple, with minimum polymer damage and more eco-friendly than the sodium hypochlorite lysis method.

Valorization of waste glycerol for the production of poly (3-hydroxybutyrate) and poly (3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer by Cupriavidus necator and extraction in a sustainable manner.

Glycerol is a by-product of many industrial processes and huge amounts of it are generated in the form of waste, thereby necessitating a search for the method of its disposal. An interesting solution is the valorization of crude glycerol into value added product such as polyhydroxyalkanoates (PHAs). The feasibility of producing PHAs by Cupriavidus necator was evaluated using crude glycerol (WG). Various cultivation strategies were designed for the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer by adding different organic acids as precursors at different concentrations levels. Batch cultivation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production showed accumulation of 6.76g/L biomass containing 4.84g/L copolymer on WG with a maximum 3-hydroxyvalerate content of 24.6mol%. PHAs extraction using a non-toxic and recyclable solvent, 1,2 propylene carbonate, showed the highest recovery yield (90%) and purity (93%) at 120°C temperature and 30min incubation. This is the first report on jatropha based glycerol valorization for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production coupled with extraction using non-toxic solvent.

Extraction of polyhydroxyalkanoates from mixed microbial cultures: Impact on polymer quality and recovery.

Polyhydroxyalkanoates (PHAs) can be extracted from mixed microbial cultures (MMCs) by means of dimethyl carbonate (DMC) or combination of DMC and sodium hypochlorite (NaClO). The protocol based on DMC, a green solvent never used before for the extraction of PHAs from MMC, allows an overall polymer recovery of 63%; also the purity and the molecular weight of the recovered polymers are good (98% and 1.2 MDa, respectively). The use of NaClO pretreatment before DMC extraction increases the overall PHA recovery (82%) but lowers the mean molecular weight to 0.6-0.2 MDa. A double extraction with DMC results to be the method of choice for the recovery of high quality PHAs from attractive but challenging MMCs.