Bench-scale and field-scale evaluation of catechol 2,3-dioxygenase specific primers for monitoring BTX bioremediation

The objective of this work was to test a molecular genetic method for in situ monitoring of aerobic benzene, toluene, and xylene (BTX) biodegrading microorganisms. Catechol 2,3-dioxygenase (C23DO) genes occur in bacteria that biodegrade benzene, toluene, xylenes, phenol, biphenyl, and naphthalene. A competitive quantitative polymerase chain reaction (QC-PCR) technique using a single set of primers specific for an entire subfamily of C23DO genes was recently developed. To determine whether bacteria containing these C23DO genes actually exist in environments contaminated by BTX, aerobic microcosms containing previously uncontaminated soil were amended with different aromatic hydrocarbons and DNA extracts were analyzed by QC-PCR for C23DO genes. Anaerobic microcosms were established to confirm that oxygen was also necessary for the enrichment of C23DO genes. Field testing was done at two sites undergoing monitored natural attenuation. In microcosm experiments naphthalene, m-xylene, and p-xylene strongly enriched for C23DO genes while benzene, toluene, and o-xylene produced only transient, weakly detectable genes. In the field study, C23DO genes were detected in groundwater samples contaminated with either xylenes or naphthalene. The results of this study demonstrated that molecular genetic techniques can provide an accurate and rapid method to detect microorganisms capable of aromatic hydrocarbon biodegradation. Such a technique would be useful for monitoring the effectiveness of aeration technologies and for documenting microbial processes for monitored natural attenuation.     

伊萨鼎力支持经销商亮相行业展会

正近日,伊萨鼎力支持旗下两家授权经销商——汕头市龙兴机电设备有限公司与吉林省力诚科技有限公司分别参加了2014中国(西部)五金与焊接设备展览会与第7届中国(长春)装备制造业博览会。展会期间,伊萨经销商重点展出并演示了伊萨全新BuddyTM系列焊接电源、全新逆变高效率轻便型气保焊机     

Banana peel: an effective biosorbent for aflatoxins

This work reports the application of banana peel as a novel bioadsorbent for in vitro removal of five mycotoxins (aflatoxins (AFB1, AFB2, AFG1, AFG2) and ochratoxin A). The effect of operational parameters including initial pH, adsorbent dose, contact time and temperature were studied in batch adsorption experiments. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pH_pzc) analysis were used to characterise the adsorbent material. Aflatoxins’ adsorption equilibrium was achieved in 15 min, with highest adsorption at alkaline pH (6–8), while ochratoxin has not shown any significant adsorption due to surface charge repulsion. The experimental equilibrium data were tested by Langmuir, Freundlich and Hill isotherms. The Langmuir isotherm was found to be the best fitted model for aflatoxins, and the maximum monolayer coverage (Q₀) was determined to be 8.4, 9.5, 0.4 and 1.1 ng mg^?1 for AFB1, AFB2, AFG1 and AFG2 respectively. Thermodynamic parameters including changes in free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were determined for the four aflatoxins. Free energy change and enthalpy change demonstrated that the adsorption process was exothermic and spontaneous. Adsorption and desorption study at different pH further demonstrated that the sorption of toxins was strong enough to sustain pH changes that would be experienced in the gastrointestinal tract. This study suggests that biosorption of aflatoxins by dried banana peel may be an effective low-cost decontamination method for incorporation in animal feed diets.     

Assessment of natural attenuation via in situ reductive dechlorination of polychlorinated biphenyls in sediments of the Twelve Mile Creek arm of Lake Hartwell, SC

Polychlorinated biphenyl (PCB)-contaminated sediment cores taken from five locations in Lake Hartwell, SC, with an increasing distance from the point source were evaluated for the presence of in situ reductive dechlorination of PCBs on the basis of a comparative congener-specific analysis of PCB distribution profiles between historical (1987) and current (1998) sediments from the same sites. A layer of 1998 sediment that was equivalent to 1987 sediment was determined by direct comparison of total PCB depth profiles after correction for any sedimentation that occurred at each location since 1987. Natural capping of contaminated sediments with the continued deposition of new sediments was observed in all locations except the one farthest from the source area. The residual PCB congeners accumulated in the field samples did not vary from site to site. Certain PCB congeners (e.g., 236-24 + 34-34, 245-25, and 23-4 CB) decreased with time and with depth along with an increase in lower chlorinated PCB congeners in all sampling locations. A similarity in distribution profiles between dechlorinated PCBs in laboratory microcosms and in the field samples was observed. These results provide supporting evidence that in situ reductive dechlorination has occurred in the Twelve Mile Creek arm of Lake Hartwell. Several sediment layers, particularlythe sites with highest PCB concentration, showed similar PCB distribution profiles between 1987 and 1998. An additional change in chlorine distribution between 1987 and 1998 at most "equivalent" depths was not observed. The ortho- and para-substituted congeners that accumulated during dechlorination of Aroclor 1254 after nearly 1 yr of incubation in the laboratory were the prominent residual products in all field samples. At a few locations and depths, evidence for dechlorination at surprisingly low concentrations (1-5 ppm) was observed. These results confirm that in situ reductive dechlorination of PCBs is operating at a very slow rate and may have been at a plateau since 1987 for certain depths and certain locations.     

Eugenol,citral, and hexanal,alone or in combination with heat,affect viability,biofilm formation,and swarming on Shiga-toxin-producing Escherichia coli

Shiga-toxin-producing Escherichia coli strains are pathogenic for humans and cause mild to severe illnesses. In this study, the antimicrobial effect of citral, eugenol, and hexanal in combination with heat shock (HS) was evaluated in terms of the growth, biofilm formation, swarming, and expression of virulence genes of STEC serotypes (O157:H7, O103, O111, and O26). Eugenol was the most effective compound against the growth of E. coli strains (MBC = 0.58 to 0.73 mg/mL), followed by citral (MBC = 0.86 to 1.26 mg/mL) and hexanal (MBC = 2.24 to 2.52 mg/mL). Biofilm formation and swarming motility have great variability between STEC strains. Natural compounds—alone or combined with HS—inhibited biofilm formation; however, swarming motility was induced by most treatments. The expression of the studied genes during biofilm formation and swarming under natural antimicrobials was affected but not in a uniform pattern. These treatments could be used to control contamination of STEC and inhibit biofilm formation.