An overview of the modification methods of activated carbon for its water treatment applications

A key challenge in environmental remediation is the design of adsorbents bearing an abundance of accessible chelating sites with high affinity, to achieve both rapid uptake and high capacity for the contaminants. Herein, we demonstrate how two-dimensional covalent organic frameworks (COFs) with well-defined mesopore structures display the right combination of properties to serve as a scaffold for decorating coordination sites to create ideal adsorbents. The proof-of-concept design is illustrated by modifying sulfur derivatives on a newly designed vinyl-functionalized mesoporous COF (COF-V) via thiol–ene “click” reaction. Representatively, the material (COF-S-SH) synthesized by treating COF-V with 1,2-ethanedithiol exhibits high efficiency in removing mercury from aqueous solutions and the air, affording Hg2+ and Hg0 capacities of 1350 and 863 mg g–1, respectively, surpassing all those of thiol and thioether functionalized materials reported thus far. More significantly, COF-S-SH demonstrates an ultrahigh ...

Postsynthetically Modified Covalent Organic Frameworks for Efficient and Effective Mercury Removal.

Surface modifications for the effective dispersion of carbon nanotubes in solvents and polymers

http://cleanaircarolina.org/wp-content/uploads/2011/06/Mercury-exposure-and-childrens-health.pdf

Mercury Exposure and Children’s Health

The optimization of engineered metabolic pathways requires careful control over the levels and timing of metabolic enzyme expression. Optogenetic tools are ideal for achieving such precise control, as light can be applied and removed instantly without complex media changes. Here we show that light-controlled transcription can be used to enhance the biosynthesis of valuable products in engineered Saccharomyces cerevisiae. We introduce new optogenetic circuits to shift cells from a light-induced growth phase to a darkness-induced production phase, which allows us to control fermentation with only light. Furthermore, optogenetic control of engineered pathways enables a new mode of bioreactor operation using periodic light pulses to tune enzyme expression during the production phase of fermentation to increase yields. Using these advances, we control the mitochondrial isobutanol pathway to produce up to 8.49 ± 0.31 g l-1 of isobutanol and 2.38 ± 0.06 g l-1 of 2-methyl-1-butanol micro-aerobically from glucose. These results make a compelling case for the application of optogenetics to metabolic engineering for the production of valuable products.

/pdf/optogenetic-regulation-of-engineered-cellular-metabolism-for-42gjwgz0o6.pdf

Optogenetic regulation of engineered cellular metabolism for microbial chemical production

The projected increase in the use of compact fluorescent lamps (CFLs) motivates the development of methods to manage consumer exposure to mercury and its environmental release at the end of lamp life. This work characterizes the time-resolved release of mercury vapor from broken CFLs and from underlying substrates after removal of glass fragments to simulate cleanup. In new lamps, mercury vapor is released gradually in amounts that reach 1.3 mg or 30% of the total lamp inventory after four days. Similar time profiles but smaller amounts are released from spent lamps or from underlying substrates. Nanoscale formulations of S, Se, Cu, Ni, Zn, Ag, and WS2 are evaluated for capture of Hg vapor under these conditions and compared to conventional microscale formulations. Adsorption capacities range over 7 orders of magnitude, from 0.005 (Zn micropowder) to 188 000 microg/g (unstabilized nano-Se), depending on sorbent chemistry and particle size. Nanosynthesis offers clear advantages for most sorbent chemistries. Unstabilized nano-selenium in two forms (dry powder and impregnated cloth) was successfully used in a proof-of-principle test for the in situ, real-time suppression of Hg vapor escape following CFL fracture.

Mercury Vapor Release from Broken Compact Fluorescent Lamps and In Situ Capture by New Nanomaterial Sorbents

Engineering control of metabolic pathways is important to improving product titers and yields. Traditional methods such as overexpressing pathway enzymes and deleting competing ones are restricted by the interdependence of metabolic reactions and the finite nature of cellular resources. Here, we developed a metabolite valve that controls glycolytic flux through central carbon metabolism in Saccharomyces cerevisiae. In a Hexokinase 2 and Glucokinase 1 deleted strain (hxk2Δglk1Δ), glucose flux was diverted away from glycolysis and into a model pathway, gluconate, by controlling the transcription of Hexokinase 1 with the tetracycline transactivator protein (tTA). A maximum 10-fold decrease in hexokinase activity resulted in a 50-fold increase in gluconate yields, from 0.7% to 36% mol/mol of glucose. The reduction in glucose flux resulted in a significant decrease in ethanol byproduction that extended to semianaerobic conditions, as shown in the production of isobutanol. This proof-of-concept is one of the first demonstrations in S. cerevisiae of dynamic redirection of glucose from glycolysis and into a heterologous pathway.

/pdf/controlling-central-carbon-metabolism-for-improved-pathway-1mz7t5xf39.pdf

Controlling Central Carbon Metabolism for Improved Pathway Yields in Saccharomyces cerevisiae

D-Glucaric acid can be produced as a value-added chemical from biomass through a de novo pathway in Escherichia coli. However, previous studies have identified pH-mediated toxicity at product concentrations of 5 g/L and have also found the eukaryotic myo-inositol oxygenase (MIOX) enzyme to be rate-limiting. We ported this pathway to Saccaromyces cerevisiae, which is naturally acid-tolerant and evaluate a codon-optimized MIOX homologue. We constructed two engineered yeast strains that were distinguished solely by their MIOX gene - either the previous version from Mus musculus or a homologue from Arabidopsis thaliana codon-optimized for expression in S. cerevisiae - in order to identify the rate-limiting steps for D-glucaric acid production both from a fermentative and non-fermentative carbon source. myo-Inositol availability was found to be rate-limiting from glucose in both strains and demonstrated to be dependent on growth rate, whereas the previously used M. musculus MIOX activity was found to be rate-limiting from glycerol. Maximum titers were 0.56 g/L from glucose in batch mode, 0.98 g/L from glucose in fed-batch mode, and 1.6 g/L from glucose supplemented with myo-inositol. Future work focusing on the MIOX enzyme, the interplay between growth and production modes, and promoting aerobic respiration should further improve this pathway.

Shawn Manchester

Papers

Mercury Vapor Release from Broken Compact Fluorescent Lamps and In Situ Capture by New Nanomaterial Sorbents

Controlling Central Carbon Metabolism for Improved Pathway Yields in Saccharomyces cerevisiae

Porting the synthetic D-glucaric acid pathway from Escherichia coli to Saccharomyces cerevisiae.

High capacity mercury adsorption on freshly ozone-treated carbon surfaces