Aerobic mineralization of chlorobenzoates by a natural polychlorinated biphenyl-degrading mixed bacterial culture

The effects of surfactant physicochemical properties, such as the hydrophile-lipophile balance (HLB) and molecular structure, on the biodegradation of 2% w/v Bow River crude oil by a mixed-bacterial culture were examined. Viable counts increased 4.6-fold and total petroleum hydrocarbon (TPH) biodegradation increased 57% in the presence of Igepal CO-630, a nonylphenol ethoxylate (HLB 13, 0.625 g/L). Only the nonylphenol ethoxylate with an HLB value of 13 substantially enhanced biodegradation. The surfactants from other chemical classes with HLB values of 13 (0.625 g/L) had no effect or were inhibitory. TPH biodegradation enhancement by Igepal CO-630 occurred at concentrations above the critical micelle concentration. When the effect of surfactant on individual oil fractions was examined, the biodegradation enhancement for the saturate and aromatic fractions was the same. In all cases, biodegradation resulted in increased resin and asphaltene concentrations. Optimal surfactant concentrations for TPH biodegradation reduced resin and asphaltene formation. Chemical surfactants have the potential to improve crude oil biodegradation in complex microbial systems, and surfactant selection should consider factors such as molecular structure, HLB, and surfactant concentration.Key words: mixed culture, crude oil, surfactant, hydrophile-lipophile balance, biodegradation.

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Enrichment of an Endosulfan-Degrading Mixed Bacterial Culture

Applied and Environmental Microbiology ◽

10.1128/aem.66.7.2822-2828.2000 ◽

2000 ◽

Vol 66 (7) ◽

pp. 2822-2828 ◽

Cited By ~ 116

Author(s):

Tara D. Sutherland ◽

Irene Horne ◽

Michael J. Lacey ◽

Rebecca L. Harcourt ◽

Robyn J. Russell ◽

...

Keyword(s):

Bacterial Culture ◽

Parent Compound ◽

Tween 80 ◽

Sole Source ◽

Gas Chromatography Mass Spectrometry ◽

Mixed Bacterial Culture ◽

Chemical Hydrolysis ◽

History Of ◽

Hydrolyzing Enzymes ◽

Polar Product

ABSTRACT An endosulfan-degrading mixed bacterial culture was enriched from soil with a history of endosulfan exposure. Enrichment was obtained by using the insecticide as the sole source of sulfur. Chemical hydrolysis was minimized by using strongly buffered culture medium (pH 6.6), and the detergent Tween 80 was included to emulsify the insecticide, thereby increasing the amount of endosulfan in contact with the bacteria. No growth occurred in control cultures in the absence of endosulfan. Degradation of the insecticide occurred concomitant with bacterial growth. The compound was both oxidized and hydrolyzed. The oxidation reaction favored the alpha isomer and produced endosulfate, a terminal pathway product. Hydrolysis involved a novel intermediate, tentatively identified as endosulfan monoaldehyde on the basis of gas chromatography-mass spectrometry and chemical derivatization results. The accumulation and decline of metabolites suggest that the parent compound was hydrolyzed to the putative monoaldehyde, thereby releasing the sulfite moiety required for growth. The monoaldehyde was then oxidized to endosulfan hydroxyether and further metabolized to (a) polar product(s). The cytochrome P450 inhibitor, piperonyl butoxide, did not prevent endosulfan oxidation or the formation of other metabolites. These results suggest that this mixed culture is worth investigating as a source of endosulfan-hydrolyzing enzymes for use in enzymatic bioremediation of endosulfan residues.

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