Biodegradation of kerosene: Study of growth optimization and metabolic fate of P. janthinellum SDX7

Penicillum janthinellum SDX7 was isolated from aged petroleum hydrocarbon-affected soil at the site of Anand, Gujarat, India, and was tested for different pH, temperature, agitation and concentrations for optimal growth of the isolate that was capable of degrading upto 95%, 63% and 58% of 1%, 3% and 5% kerosene, respectively, after a period of 16 days, at optimal growth conditions of pH 6.0, 30 °C and 180 rpm agitation. The GC/MS chromatograms revealed that then-alkane fractions are easily degraded; however, the rate might be lower for branched alkanes, n-alkylaromatics, cyclic alkanes and polynuclear aromatics. The test doses caused a concentration-dependent depletion of carbohydrates of P. janthinellum SDX7 by 3% to 80%, proteins by 4% to 81% and amino acids by 8% to 95% upto 16 days of treatment. The optimal concentration of 3% kerosene resulted in the least reduction of the metabolites of P. janthinellum such as carbohydrates, proteins and amino acids with optimal growth compared to 5% and 1% (v/v) kerosene doses on the 12th and 16th day of exposure. Phenols were found to be mounted by 43% to 66% at lower and higher concentrations during the experimental period. Fungal isolate P. janthinellum SDX7 was also tested for growth on various xenobiotic compounds.

Validation of computationally predicted substrates for laccase

Present study reports the validation (oxidation) of computationally predicted oxidation of xenobiotic contaminants by commercially available pure laccase from Trametes versicolor. Selected contaminants were predicted as potential targets for laccase oxidation by using in-silico docking tool. The oxidation by laccase was measured by change in absorbance at specific λ max of each compound. Sinapic acid and tyrosine were taken as positive and negative controls, respectively. Oxidation was observed in m-chlorophenol, 2,4 di-chlorophenol, 2,4,6 tri-chlorophenol, captan, atrazine and thiodicarb, except malathion, which showed no activity. It could be speculated that the predicted substrates showing oxidation shared homology at structural and chemical level with positive control compounds. In case of malathion, structural non-homology with sinapic acid could be attributed to its inactivity towards laccase that required further structural analysis. Thus, a remediation tool proposing an advanced remediation approach combining the application of theoretical in-silico method and subsequent experimental validation using pure laccase could be proposed. As number and type of xenobiotics increase, the unfeasibility to screen them experimentally for bioremediation also rise. This approach would be useful to reduce the time and cost required in other screening methods.

Biodegradation of wastewater of Najafgarh drain, Delhi using autochthonous microbial consortia : a laboratory study.

There are seventeen drains, which discharge their untreated urban and industrial wastewaters into the Delhi segment of river Yamuna. The Najafgarh drain is the first and the largest drain, and it alone contributes 1667.84 mld i.e. 60% of the total wastewater discharge into the river Yamuna and as such add 81.36 tons of BOD load per day. As per the available data approximately 95% of the wastewater of this drain is biodegradable. In the present study, an attempt has been made to reduce the BOD load and COD levels of wastewater of Najafgarh drain using autochthonous microbial consortium. During this study the raw wastewater samples were treated for 6 h time interval with different concentration of consortium. It was observed that by increasing the existing microbial population in the wastewater sample by 150-200% there is a significant decrease in BOD and COD levels. Finally, BOD/COD ratios before and after biotreatment have been analyzed to assess the efficacy of the natural consortium.