maleic-acid and phthalic-acid

The ubiquitous presence of the plasticizer di (2-ethylhexyl) phthalate (DEHP) in the environment is of concern due to negative biological effects associated with it and its metabolites. In particular, the metabolite mono (2-ethylhexyl) phthalate (MEHP) is a potential endocrine disruptor. Earlier work had identified the diester di (2-ethylhexyl) maleate (DEHM) as a potential greener candidate plasticizer to replace DEHP, yet its biodegradation rate was reported to be slow. In this study, we modified the side chains of maleate diesters to be linear (i.e., unbranched) alkyl chains that varied in length from ethyl to n-octyl. The plasticization efficiency of these compounds blended into PVC at 29 wt.% increased with the overall length of the molecule, but all compounds performed as well as or better than comparable samples with DEHP. Tests conducted with the equally long DEHM and dihexyl maleate (DHM) showed that branching has no effect on glass transition temperature (Tg) reduction efficiency. Biodegradation experiments with the common soil bacterium Rhodococcus rhodocrous in the presence of the plasticizer showed acceptable hydrolysis rates of maleates with unbranched side chains, while the branched DEHM showed almost no degradation. The addition of hexadecane as auxiliary carbon source improved hydrolysis rates. Temporary buildup of the respective monoester of the compounds were observed, but only in the case of the longest molecule, dioctyl maleate (DOM), did this buildup lead to growth inhibition of the bacteria. Maleates with linear side chains, if designed and tested properly, show promise as potential candidate plasticizers as replacements for DEHP.

Topics: Biodegradation, Environmental; Diethylhexyl Phthalate; Endocrine Disruptors; Environmental Pollution; Green Chemistry Technology; Maleates; Phthalic Acids; Plasticizers; Rhodococcus

Corynebacterium glutamicum is generally regarded as a safe microorganism and is used to produce many biochemicals, including L-glutamate. 5-Aminolevulinic acid (ALA) is an L-glutamate derived non-protein amino acid, and is widely applied in fields such as medicine and agriculture.. The products of the gltX, hemA, and hemL genes participate in the synthesis of ALA from L-glutamate. Their annotated C. glutamicum homologs were shown to be functional using heterologous complementation and overexpression techniques. Coexpression of hemA and hemL in native host led to the accumulation of ALA, suggesting the potential of C. glutamicum to produce ALA for research and commercial purposes. To improve ALA production, we constructed recombinant C. glutamicum strains expressing hemA and hemL derived from different organisms. Transcriptome analysis indicated that the dissolved oxygen level and Fe(2+) concentration had major effects on ALA synthesis. The downstream pathway of heme biosynthesis was inhibited using small molecules or introducing genetic modifications. Small-scale flask cultures of engineered C. glutamicum produced 1.79 g/L of ALA.. Functional characterization of the key enzymes indicated complex regulation of the heme biosynthetic pathway in C. glutamicum. Systematic analysis and molecular genetic engineering of C. glutamicum may facilitate its development as a system for large-scale synthesis of ALA.

Topics: Aldehyde Oxidoreductases; Aminolevulinic Acid; Bacterial Proteins; Corynebacterium glutamicum; Escherichia coli; Glucose; Glutamate-tRNA Ligase; Intramolecular Transferases; Levulinic Acids; Maleates; Metabolic Engineering; Phthalic Acids

To better understand the behavior of low molecular weight organic acids in subsurface environments, the transport of three dicarboxylic acids (phthalic, maleic, and fumaric acid) in water-saturated columns packed with a hematite-coated sand was investigated in single and binary organic acid systems. Experiments were conducted at a single ionic strength (0.1M) and at two pH values (4.1 and 5.3). In single-acid systems, the order of breakthrough at both pH values was fumaric acid, followed by maleic acid, and then phthalic acid. The shape of the breakthrough curves for the acids at the two pH values were similar except at pH 5.3 phthalic acid showed two adsorption fronts. The initial front only partially broke through, whereas the second front proceeded to complete breakthrough. This behavior resulted from a marked pH increase during phthalic acid adsorption and suggests that the single-acid systems behaved as dual-component systems with the organic acid and hydrogen ion as variables. The breakthrough curves for the binary organic acid systems showed organic acids with a higher adsorption affinity (e.g., phthalic acid) competitively displace organic acids with a lower adsorption affinity (e.g., fumaric acid). The dual-component effect observed for phthalic acid in the single-acid systems was suppressed in the mixed acid systems, perhaps reflecting pH changes that accompanied the desorption of the weakly-binding acids. These results may provide an important step toward further elucidating the processes controlling organic acid fractionation in the subsurface.

Topics: Adsorption; Chromatography; Fumarates; Hydrogen-Ion Concentration; Maleates; Phthalic Acids; Porosity; Silicon Dioxide

A CE method for the determination of the ethanol consumption marker ethyl sulfate (EtS) in human urine was developed. Analysis was performed in negative polarity mode with a background electrolyte composed of 15 mM maleic acid, 1 mM phthalic acid, and 0.05 mM cetyltrimethylammonium bromide (CTAB) at pH 2.5 and indirect UV detection at 220 nm (300 nm reference wavelength). This buffer system provided selective separation conditions for EtS and vinylsulfonic acid, employed as internal standard, from urine matrix components. Sample pretreatment of urine was minimized to a 1:5 dilution with water. The optimized CE method was validated in the range of 5-700 mg/L using seven lots of urine. Intra- and inter-day precision and accuracy values, determined at 5, 60, and 700 mg/L with each lot of urine, fulfilled the requirements according to common guidelines for bioanalytical method validation. The application to forensic urine samples collected at autopsies as well as a successful cross-validation with a LC-MS/MS-based method confirmed the overall validity and real-world suitability of the developed expeditious CE assay (sample throughput 130 per day).

Topics: Adult; Alcohol Drinking; Biomarkers; Buffers; Cetrimonium; Cetrimonium Compounds; Chromatography, Liquid; Electrophoresis, Capillary; Ethanol; Female; Forensic Toxicology; Humans; Male; Maleates; Phthalic Acids; Spectrophotometry, Ultraviolet; Sulfuric Acid Esters

(1) In order to explore the possible mechanism that organic reagents used in the incubation step of the plasma renin activity (PRA) analysis act as a angiotensinase inhibitors we did angiotensin I (AI) recovery studies from plasma with such reagents. The organic acids and their mean difference in percent recovery of AI as compared to that for hydrochloric acid (HCI) are respectively as follows for one and a three hour incubation time: maleic (0.7%, 4.5%); and potassium hydrogen phthalate (KHphthalate) (7.2%, 9.6%). The tris(hydroxymethyl)aminomethane (Tris) organic acid salts and their mean difference in percent recovery of AI as compared to that for Tris-HCl are as follows for a one hour incubation: Tris-acetylsalicylate (3.6%), Tris-phenoxyacetate (3.6%), Tris-benzoate (2.6%), and Tris-salicylate (4.9%). (2) Of the reagents studied KHphthalate after a three hour incubation produced a statistically significant difference from the HCl reagent. The recovery data for all the organic reagents suggested that the primary mechanism of action was not that of an angiotensinase inhibitory one.

Topics: Angiotensin I; Angiotensins; Aspirin; Benzoates; Buffers; Humans; Hydrochloric Acid; Maleates; Phenoxyacetates; Phthalic Acids; Protease Inhibitors; Salicylates; Tromethamine