Characterization of hydrophobic organic contaminant biodegradation by COD analysis

Biodegradation of hydrophobic organic contaminants is often accompanied by the accumulation of hydrophobic intermediates. This paper is devoted to the experimental evaluation of electron balance between the hydrophobic intermediates and the other biodegradation products. The ratio of the fraction of electrons that are not held in the hydrophobic intermediates to the total fraction of electrons released from the substrate during its conversion is called a degradation level (DL). Under certain conditions, the DL value is equal to the angular coefficient of the plot in the coordinates (1−(S/S0);1−(COD/COD0)), where S and COD are current values of substrate concentration and chemical oxygen demand of the ethylacetate extract from the culture; S0 and COD0 are the respective initial values. This approach has been used for analysis of the conversion of PAHs by Sphingomonas sp. VKM B-2434. The DL values obtained correspond well to most published data on PAH metabolism by this strain. The DL values significantly increased as a result of addition of the strains consuming the products of conversion of PAHs by Sphingomonas sp. VKM B-2434. The proposed method seems useful for characterizing biodegradation of hydrophobic pollutants by both pure and mixed microbial cultures.

► We propose method for characterization of hydrophobic contaminant biodegradation.
► Dynamics of substrate concentration and COD of the culture extract are measured.
► Electron balance between hydrophobic and non-hydrophobic products is evaluated.