Impact of Tillage, Crop Rotation, and Chemical Management Practices on Groundwater Quality

Contamination of groundwater by nitrate and pesticides has been documented by various state and federal agencies in the United States. Groundwater pollution is of increasing concern in the United States because about 50 percent of the drinking water comes from groundwater. A recent study suggested that water pollution is the most damaging and widespread environmental effect of agricultural production. Recent research conducted in Iowa and surrounding states has indicated the incidence of groundwater contamination by pesticides and nitrogen fertilizers (Baker and Johnson, 1981; Everts and Kanwar, 1990; Gast et al., 1978; Hallet al., 1989; Hallberg, 1989; Kanwar et al., 1985a, 1986, 1988, 1991). Elevated nitrate levels in groundwater because of agricultural activities also have been documented (Kanwar and Baker, 1991)

Purification and characterization of a low molecular mass alkaliphilic lipase of Bacillus cereus MTCC 8372

A low molecular mass alkaliphilic extra-cellular lipase of Bacillus cereus MTCC 8372 was purified 35-fold by hydrophobic interaction (Octyl-Sepharose) chromatography. The purified enzyme was found to be electrophoretically pure by denaturing gel electrophoresis and possessed a molecular mass of approximately 8 kDa. It is a homopentamer of 40 kDa as revealed by native-PAGE. The lipase was optimally active at 55 &deg;C and retained approximately half of its original activity after 40 min incubation at 55 &deg;C. The enzyme was maximally active at pH 8.5. Mg 2+ , Cu 2+ , Ca 2+ , Hg 2+ , Al 3+ and Fe 3+ at 1 mM enhanced hydrolytic activity of the lipase. Interestingly, Hg 2+ ions synergized and Zn 2+ and Co 2+ ions antagonized the lipase activity. Among surfactants, Tween 80 promoted the lipase activity. Phenyl methyl sulfonyl fluoride (PMSF, 15 mM) decreased 98% of original activity of lipase. The lipase was highly specific towards p -nitrophenyl palmitate and showed a V max and K m of 0.70 mmol.mg &minus;1 .min &minus;1 and 32 mM for hydrolysis of p NPP.<br /