RESUMO
A novel aerobic gram-negative bacterial strain capable of utilizing 2-hydroxyquinoxaline (2-HQ) as sole source of carbon and energy was isolated from Indian agricultural soil and named as HQ1. Strain HQ1 was identified as Ochrobactrum sp. on the basis of morphology, physico-biochemical characteristics and 16S rRNA sequence analysis. The generation time of Ochrobactrum sp. HQ1 on 2-HQ at log phase is 0.71 h or 42.6 min. The degradation of 2-HQ by HQ1 under various physico-chemical parameters was analysed by HPLC and observed to be optimum with a high inoculum density (1.0 OD) at pH 7-8, temperatures 37-40°C and a high concentration of 2-HQ (500 ppm). Degradation of 2-HQ was also improved when additional nitrogen sources were used and this was attributed to the enhanced growth of the bacterium on the readily available nitrogen sources. Analysis of 2-HQ degradation by GC-MS resulted in elucidation of the degradation pathway for HQ1, a novel observation for aerobic Gram-negative bacteria. These findings are a possible indication of the application of HQ1 in the bioremediation of pesticide/metabolite contamination.
RESUMO
A simple, sensitive and rapid differential pulse polarographic method has been developed for the quantitative determination of organophosphorus pesticides such as dicrotophos, crotoxyphos and chlorfenvinphos in agricultural formulations in universal buffers of a pH range 2.0-12.0. The sample is treated with ethanol to facilitate the dissolution of these pesticides. Both standard addition and calibration methods can be used for the analyses. The lower detection limits are 1.25x10(-9), 1.05x10(-9) and 1.0x10(-9) M, respectively. The method can be applied successfully to determination of these pesticides in grains and soil.