The endosulfan-degrading bacterial strain Pseudomonas fluorescens was isolated, and degradation of endosulfan by freely suspended and calcium-alginate entrapped bacterial cells were investigated in batch as well as in packed bed column studies. Freely suspended Pseudomonas fluorescens cells with biomass maximum OD/OD 0 value of 1.68 at 610 nm could degrade endosulfan with an initial concentration of 350.24±0.83 μg/L efficiently within 12 days, thus utilising endosulfan as the sole carbon and energy source. Degradation of endosulfan occurred concomitantly with bacterial growth. The bacteria immobilised in Caalginate beads in batch shake flask system were tested for their ability to degrade endosulfan at different concentrations (350.24±0.83, 450.39±1.95 and 550.85±1.84 μg/L). A total of 125 mL of Broth minimal medium of pH 7 was inoculated with 5 g of wet Ca-alginate beads (derived from a 3-mL cell suspension of 0.72 OD at 610 nm) for the study. Almost similar trends of degradation efficiencies were shown by the immobilised cells toward different concentrations of endosulfan. The complete removal of alpha and beta-isomers of endosulfan at different initial endosulfan concentrations was observed between 9 and 11 days of the experiment. Additionally, the degradation rate in batch reactors with Ca-alginate-immobilised cells also derived from a 3-mL cell suspension of 0.72 OD at 610 nm was tested and found to be marginally higher than that of free cells. Ca-alginate immobilised cells in packed bed reactors operated in a semi-continuous mode could degrade toxic alpha and beta-isomers of endosulfan (350.38±1.18 μg/L) within 6 days. Thus, the method proved effective for biodegradation of endosulfan. The metabolites formed indicated that the degradation of the pesticide follows a hydrolytic pathway.

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<p><strong>Abstract.</strong> The microbial contamination of water is a world-wide environmental problem. Many traditional methods are being used in various parts of the world to purify the water. According to World Health Organization, 80% of world's population living in rural areas relies on herbal traditional medicines as their primary health care. So the study on properties and uses of medicinal plants are subject to growing interests. An attempt was made to assess the antibacterial properties of certain selected herbs such as <i>Ocimum sanctum</i> (Krishna Tulsi), <i>Ocimum kilimandscharicum</i> (Karpoora Tulsi), <i>Ocimum tenuiflorum</i> (Ram Tulsi), <i>Azadirachta indica</i> (Neem), <i>Simarouba glauca</i> (bitterwood), <i>Caesalpinia sappan</i> (Pathimugam), <i>Cuminum cyminum</i> (Jeerakam), <i>Vetiveria zizanioides</i> (Ramacham), <i>Saraca indica</i> (Ashoka tree) and <i>Murraya koenigii</i> (curry leaves) against different bacteria such as total coliforms, faecal coliforms, <i>Escherichia coli</i>, <i>Bacillus</i> sp. and <i>Serratia</i> sp. The antibacterial activity of the plant extracts was determined by spread plate method, Kirby–Bauer disc diffusion method, most probable number (MPN) method and Petrifilm method. The shelf life of the herbal extract <i>Ocimum sanctum</i> (Krishna Tulsi) was also determined using a UV-visible spectrophotometer. A comparison study of the antibacterial efficiency of the three varieties of <i>Ocimum sanctum, Ocimum kilimandscharicum</i> and <i>Ocimum tenuiflorum</i> was also done. After the complete analysis of the antibacterial activity of different herbs, <i>Ocimum sanctum</i>, the most efficient herb, was selected and treatment methods based on the herb were developed so that it can be used conveniently in various households. Therefore <i>Ocimum sanctum</i> plant can be further subjected to isolation of therapeutic antimicrobial and pharmacological evaluation.</p>

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