Physico-chemical treatments for enhancement of microbial metabolism of xenobiotics

Many xenobiotic chemicals resists biodegradation, but their recalcitrant bonds are sensitive to photolysis. Although photolytic treatment to complete degradation would be too costly, the stimulatory effect of a brief photolysis on subsequent biodegradation of the model pollutants 2,4-dichlorophenol, 2,4,5-trichlorophenol, benzo(a)pyrene, 2,2', 4,4', 5,5'-hexachlorobiphenyl, 1,2,4-trichlorobenzene and paranitrotoluene was evaluated in the first part of this study. Hydrogen peroxide was added in some cases as an oxidant to decrease photolysis time. Using 14C-labeled model compounds, intact and photolyzed solutions were incubated in soil and sewage sludge test systems. Biodegradation was followed by measuring 14CO2 evolution and by periodic determinations of solvent-extractable and bound residues, allowing quantitative recovery of applied radiocarbon in most cases. Photolytic treatment greatly increased 14CO2 evolution and bound residues resulting in large decreases of solvent-extractable activity. The second part of this study developed a non-destructive method for differentiating these tow possibilities. Two n-alkanes, octadecane (C18) and hexatriacontane (C36), the latter molecule being essentially recalcitrant in the environment, were packaged into liposomes. Uptake and metabolism rates of packaged versus unpackaged substrates were then compared