Sorption behavior of dibutyl phthalate and dioctyl phthalate by aged refuse

Systematic metabolic engineering of Escherichia coli for the enhanced production of cinnamaldehyde

Cinnamaldehyde (CAD) derived from cinnamon bark has received much attention for its potential as a nematicide and food additive. Previously, we have succeeded in developing an Escherichia coli strain (YHP05) capable of synthesizing cinnamaldehyde; however, the production titer (75 mg/L) was not sufficient for commercialization. Herein, to develop an economical and sustainable production bioprocess, we further engineered the YHP05 strain for non-auxotrophic, antibiotic-free, inducer-free hyperproduction of CAD using systematic metabolic engineering. First, the conversion of trans-cinnamic acid (t-CA) to CAD was improved by the co-expression of carboxylic acid reductase and phosphopantetheinyl transferase (PPTase) genes. Second, to prevent the spontaneous conversion of CAD to cinnamyl alcohol, 10 endogenous reductase and dehydrogenase genes were deleted. Third, all expression cassettes were integrated into the chromosomal DNA using an auto-inducible system for antibiotic- and inducer-free production. Subsequently, to facilitate CAD production, available pools of cofactors (NADPH, CoA, and ATP) were increased, and acetate pathways were deleted. With the final antibiotic-, plasmid-, and inducer-free strain (H-11MPmR), fed-batch cultivations combined with in situ product recovery (ISPR) were performed, and the production titer of CAD as high as 3.8 g/L could be achieved with 49.1 mg/L/h productivity, which is the highest CAD titer ever reported.

Electrochemical degradation performance and mechanism of dibutyl phthalate with hydrophobic PbO2 electrode

A polytetrafluoroethylene (PTFE) doped PbO₂ anode with a highly hydrophobicity was fabricated by electrodeposition method. In this process, vertically aligned TiO₂ nanotubes (TiO₂NTs) are formed by the anodic oxidation of Ti plates as an intermediate layer for PbO₂ electrodeposition. The characterization of the electrodes indicated that PTFE was successfully introduced to the electrode surface, the TiO₂NTs were completely covered with β-PbO₂ particles and gave it a large surface area, which also limited the growth of its crystal particles. Compared with the conventional Ti/PbO₂ and Ti/TiO₂NTs/PbO₂ electrode, the Ti/TiO₂NTs/PbO₂-PTFE electrode has enhanced surface hydrophobicity, higher oxygen evolution potential, lower electrochemical impedance, with more active sites, and generate more hydroxyl radicals (·OH), which were enhanced by the addition of PTFE nanoparticles. The electrocatalytic performance of the three electrodes were investigated using dibutyl phthalate (DBP) as the model pollutant. The efficiency of the DBP removal of the three electrodes was in the order: Ti/TiO₂NTs/PbO₂-PTFE > Ti/TiO₂NTs/PbO₂ > Ti/PbO₂. The degradation process followed the pseudo-first-order kinetic model well, with rate constants of 0.1326, 0.1266, and 0.1041 h^-1 for the three electrodes, respectively. The lowest energy consumption (6.1 kWh g^-1) was obtained after 8 h of DBP treatment using Ti/TiO₂NTs/PbO₂-PTFE compared to Ti/TiO₂NTs/PbO₂ (6.7 kWh g^-1) and Ti/PbO₂ (7.4 kWh g^-1) electrodes. Moreover, the effects of current density, initial pH and electrolyte concentration were investigated. Finally, the products of the DBP degradation process were verified based on gas chromatography-mass spectrometry analysis, and possible degradation pathways were described.

Neurological effects of subchronic exposure to dioctyl phthalate (DOP), lead, and arsenic, individual and mixtures, in immature mice

Dioctyl phthalate (DOP) (200, 500, and 1000 mg kg^-1 bw, i.g.), Pb (Ac)₂ (50 mg L^-1, p.o.), and NaAsO₂ (10 mg L^-1, p.o.) were administered individually and as mixtures to weanling male mice for 8 weeks. It was observed that Pb, As, and DOP exposure could significantly inhibit the growth and development of mice. Compared with the Pb, As, and Pb + As groups, the activities of iNOS and TNOS were significantly increased, the levels of AChE and SOD were significantly decreased, and the level of MDA was significantly increased in the Pb + DOP-H, As + DOP-H, and Pb + As + DOP-H groups. The factorial analysis shows that the iNOS, TNOS, and AChE present synergistic effects on Pb, As, and DOP. A significant increase of escape latency and a significant decrease of original platform quadrant stops were observed between Pb + As + DOP-H and Pb + As groups. The factorial analysis shows that there was a synergistic effect on Pb, As, and DOP. Compared with that of the control group, the expression levels of caspase-3 and Bax expression in Pb + As, DOP-H, Pb + DOP-H, As + DOP-H, and Pb + As + DOP-H groups were significantly increased in the hippocampus. The expression levels of Bcl-2 expression decreased significantly and the Bax/Bcl-2 ratio increased significantly. Pathological alterations on the hippocampus were found in exposed groups. This result shows that combined exposure of Pb, As, and DOP could induce neurotoxicity, of which possible mechanism is hippocampal neuronal apoptosis. Graphical abstract This study shows that there were three components with eigenvalues greater than 1, which together explained 89.40% of total variance. The first component (PC1) showed high loadings on B-SOD, L-SOD, B-MDA, L-MDA, K-MDA, iNOS, tNOS, and AChE and accounted for 46.55% of the total variance after Varimax rotation. PC2 accounted for 23.81% of the total variance with high loadings on B-As, L-As, K-As, and K-SOD, whereas PC3 showed high loadings on B-Pb, L-Pb, and K-Pb and accounted for 19.04% of the total variance.

Removal of phthalic acid dieters with dissolved organic matter by an anaerobic/anoxic/oxic leachate treatment process

The removal of di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) with dissolved organic matter (DOM) was studied in a laboratory scale anaerobic/anoxic/oxic reactor for landfill leachate treatment. The removal rate was up to 98.0% for DBP and 78.2% for DEHP, which was related to humification of DOM (i.e., the aromaticity and molecular weight (MW) of humic substances in landfill leachate). The dissolved organic carbon (DOC) was mostly humic acid and fulvic acid in the fraction of 1–100 kDa MW, indicating strong aromaticity and a high DBP/DEHP concentration. With complete removal of the fraction, the removal rate of DBP/DEHP was also high. The positive correlation of the DOC and DBP/DEHP concentration in raw leachate and the effluent from each reactor showed that the interaction between DOM and DBP/DEHP facilitated the removal of organic pollutants.

The removal of di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) with dissolved organic matter (DOM) was studied in a laboratory scale anaerobic/anoxic/oxic reactor for landfill leachate treatment.

Variation in accumulation, transport, and distribution of phthalic acid esters (PAEs) in soil columns grown with low- and high-PAE accumulating rice cultivars

The extensive use of plasticizers containing di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) results in high residual concentrations in agricultural soils and poses potential risks to human health through the food chain. Here, two rice cultivars with low (Fengyousimiao) and high (Peizataifeng) phthalic acid ester (PAE) accumulation were grown in leaching columns packed with DBP- and DEHP-contaminated soils to investigate their transport, fraction distribution, and accumulation in soil-rice-water system. Significant differences in soil vertical distribution of DBP and DEHP were observed among the two cultivars, sterilization and non-sterilization treatments. Both DBP and DEHP could leach to the bottom layer even though their concentrations in both soil and pore water decreased along with soil depth. DBP and DEHP concentrations in pore water were significantly correlated with those in corresponding soil layer at ripening stage. The available fractions including desorbing and non-desorbing fractions were predominant in the total concentrations of DBP and DEHP of soils. DBP and DEHP storages in coarse soil fractions (i.e., coarse and fine sands) with higher bioavailability displayed higher bioconcentration factors compared to finer soil fractions (i.e., silt and clay), and bioconcentration factors of Peizataifeng were higher than those of Fengyousimiao. The variations in vertical migration and accumulation of DBP and DEHP by the two cultivars implied different adverse effects on the security of groundwater and food.

Sorption of dodecyltrimethylammonium chloride (DTAC) to agricultural soils

Quaternary ammonium compounds (QACs) used as cationic surfactants are intensively released into environment to be pollutants receiving more and more concerns. Sorption of dodecyltrimethylammonium chloride (DTAC), one of commonly used alkyl QACs, to five types of agricultural soils at low concentrations (1-50mg/L) was investigated using batch experiments. DTAC sorption followed pseudo-second-order kinetics and reached reaction equilibrium within 120min. Both Freundlich model and Langmuir model fitted well with DTAC isotherm data with the latter better. DTAC sorption was spontaneous and favorable, presenting a physical sorption dominated by ion exchanges. Sorption distribution coefficient and sorption affinity demonstrated that soil clay contents acted as a predominant phase of DTAC sorption. DTAC could display a higher mobility and potential accumulation in crops in the soils with lower clay contents and lower pH values. Sorption of DTAC was heavily affected by ions in solution with anion promotion and cation inhibition.

Effects of hydrodynamic conditions on the sorption behaviors of aniline on sediment with coexistence of nitrobenzene

The sorption behaviors of pollutants affected by hydrodynamic conditions were confirmed in natural water environment. The effects of hydrodynamic conditions on the sorption behaviors of aniline on sediment with coexistence of nitrobenzene were investigated. The particle entrainment simulator (PES) was used to simulate varied bottom shear stresses. The batch equilibrium method was applied to the experiments with the stress levels and the action time controlled at 0.2-0.5 N/m(2) and 24 h, respectively. The findings indicated that apparent partition coefficient of aniline on sediment increased with the shear stress significantly, while decreased with nitrobenzene concentration. On the contrary, both the sorption amount of aniline on suspended particulate matter (Q s) and the effect of nitrobenzene concentration on Q s declined as the shear stress increased. The sorption kinetic results showed that the sorption process followed the pseudo-second-order kinetics equation, and the process included two stages: fast sorption stage and slow sorption stage, among which the average sorption rate of fast stage was 7.5-9.5 times that of slow one. The effect of shear stress on the average sorption rate of aniline was enhanced with the increase of nitrobenzene concentration. And shear stress weakened the disturbance of cosolute on main solute sorption process. In addition, experiment results of sorption kinetic show that only the initial sorption rate was affected by shear stress and cosolute concentration. In the first 5 min, shear stress had positive effects on the sorption rate. After that, the sorption rate barely changed with shear stress and cosolute concentration.