Kinetics of phenol biodegradation at high concentration by a metabolically versatile isolated yeast Candida tropicalis PHB5

A highly tolerant phenol-degrading yeast strain PHB5 was isolated from wastewater effluent of a coke oven plant and identified as Candida tropicalis based on phylogenetic analysis. Biodegradation experiments with C. tropicalis PHB5 showed that the strain was able to utilize 99.4 % of 2,400 mg l^?1 phenol as sole source of carbon and energy within 48 h. Strain PHB5 was also observed to grow on 18 various aromatic hydrocarbons. Haldane model was used to fit the exponential growth data and the following kinetic parameters were obtained: μ _max?=?0.3407 h^?1, K _S?=?15.81 mg l^?1, K _i?=?169.0 mg l^?1 (R ²?=?0.9886). The true specific growth rate, calculated from μ _max, was 0.2113. A volumetric phenol degradation rate (V _max) was calculated by fitting the phenol consumption data with Gompertz model and specific degradation rate (q) was calculated from V _max. The q values were fitted with Haldane model, yielding following parameters: q _max?=?0.2766 g g^?1 h^?1, K _S ′?=?2.819 mg l^?1, K _i ′?=?2,093 (R ²?=?0.8176). The yield factor (Y _X/S ) varied between 0.185 to 0.96 g g^?1 for different initial phenol concentrations. Phenol degradation by the strain proceeded through a pathway involving production of intermediates such as catechol and cis,cis-muconic acid which were identified by enzymatic assays and HPLC analysis.     

Inhibition of lipid peroxidation by extracts/subfractions of Chickrassy (Chukrasia tabularis A. Juss.)

Polyphenols and polyphenol-rich fractions of plants have been reported to have protective effects against lipid peroxidation, most probably by serving as scavengers of free radicals and/or by chelating metal ions. In the present study, the effect of different extracts/subfractions of Chickrassy (Chukrasia tabularis) on peroxyl radical mediated damage to the polyunsaturated fatty acids was investigated. Liver homogenate was used as experimental material. The production of malondialdehyde served as a marker of lipid peroxidation and oxidative stress. It was observed that polyphenol-rich fractions, particularly the ethyl acetate fractions of bark and leaves, showed the highest protective activity of 83.02% and 88.62% inhibition, respectively. This study will help in knowing the scientific validation of this plant, for its use in ayurvedic formulations. The current in vitro experiments performed herewith comply with the current laws of India.     

Evaluation of detection methods for genetically modified traits in genotypes resistant to European corn borer and herbicides

Detection of genetically modified (GM) traits in corn (Zea mays L.) is urgently needed for preservation of genetic identity and marketing GM products. A laboratory study was conducted to evaluate the efficiency, accuracy, and reliability of different analytical methods to detect GM traits in corn. Samples with known fractions of GM concentrations (Bacillus thuringiensis [Bt], Liberty Link [LL] and stacked [Bt/LL] genes) from commercial seed companies and those derived from yellow kernels in a white corn ear, outcrossed by pollen of neighboring Bt hybrid, were tested by lateral flow quick test kits and by enzyme-linked immunosorbent assay (ELISA)-based test strips purchased from different companies. Liberty Link hybrids are resistant to glufosinate (Liberty or Basta) herbicides, whereas Bt corn is developed for the control of European corn borer (Ostrinia nubilalis). Selected samples of GM concentrations were also tested in a commercial laboratory using DNA-based polymerase chain reaction (PCR) test. The results demonstrated that qualitative lateral flow quick tests could detect samples containing 1% or higher Bt and 2% or higher LL concentrations within the recommended time limit of the test. Faint test lines for samples containing 0.5 to 1% Bt or 1 to 2% LL concentrations appeared if samples remained in the test cup overnight. ELISA test strips detected the Bt content semiquantitatively in the range of 0.5 to 2.0%. Grain samples derived from non-Bt corn outcrossed by neighboring Bt pollen had usually lower GM concentrations than commercial GM seed samples. Both ELISA- and DNA-based PCR tests distinguished samples with GM concentrations between 0.1 to 0.5%, but the precision of quantification at this range was very low and results were highly inconsistent.     

Retrospective monitoring of persistent organic pollutants,including PCBs,PBDEs, and polycyclic musks in blue mussels (Mytilus edulis) and sediments from New Bedford Harbor,Massachusetts, USA: 1991–2005

Blue mussels (Mytilus edulis) and sediments collected from 1991 to 2005 from New Bedford Harbor (NBH), MA, were analyzed for two polycyclic musks (HHCB or Galaxolide® and AHTN or Tonalide®), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs). HHCB and AHTN were found in mussel tissues at mean concentrations of 836 and 376 ng/g lipid weight (lw), respectively, which were two- to seven-fold higher than those found at a reference site. Mean concentrations of HHCB and AHTN in NBH sediments were 12 and 6.3 ng/g dry weight (dw), respectively. Four- and five-ringed PAHs, such as phenanthrene, anthracene, fluoranthene, and pyrene, collectively accounted for 61 % of the ∑PAHs concentrations in mussels from NBH. Mean ΣPCB concentrations in mussels from upper and lower NBH were 942 and 182 μg/g lw, respectively, and were dominated by tetra- and penta-chlorobiphenyl congeners, collectively accounting for 61 % of the ΣPCB concentrations. The mean concentration of ∑PBDEs in mussels from NBH was 277 ng/g lw, and no significant difference existed in the concentrations between upper and lower NBH. DDTs were the major OCP found in mussels, found at a mean concentration of 778 ng/g lw. The concentrations of HHCB, AHTN, ΣPBDEs, ΣPAHs, and DDTs in mussels decreased significantly (r ²?≥?0.56, p?≤?0.052) from 1991 to 2005. The concentrations of PCBs and chlordanes did not exhibit a decreasing trend in mussel tissues (r ²?<?0.50; p?>?0.076) from 1991 to 2005. Based on the temporal trends in the concentrations of HHCB, AHTN, ∑PAHs, and ∑PBDEs found in mussels from NBH, it was estimated that between 5.5 and 12 years were required for the concentrations of these compounds to decrease by half (i.e., environmental halving time) of the levels found in 1991.