Monitoring the stereoselectivity of biodegradation of chiral polychlorinated biphenyls using electrokinetic chromatography

A study of the biodegradation of several chiral polychlorinated biphenyls (PCBs, IUPAC numbers 45, 88, 91, 95, 136, 144, 149, and 176) by a naturally occurring soil bacterium as well as the stereoselectivity of such process has been performed using Electrokinetic Chromatography with cyclodextrins (CD-EKC). In order to achieve the analysis of chiral PCBs, a CD-EKC system based on 50 mM 2-morpholinoethanesulfonic acid (MES) buffer (pH 6.5) containing 2 M urea, 20 mM carboxymethylated ccyclodextrin (CM-c-CD), and 10 mM b-cyclodextrin (b-CD) was used. First, the percentage degradation of PCBs by the microorganism used in this work was measured for different incubation times (22, 46, 71, 93, 165, 213, and 262 hours). The results showed a high degree of biodegradation (from 61% to 94%) for the eight PCBs studied after 262 hours of incubation with the microorganism, degradation being favoured for the least chlorinated congeners. Secondly, measurement of the atropisomeric ratio of the PCB atropisomers during the biodegradation process revealed no significant variation of the atropisomeric ratios with the degradation time, indicating a nonstereoselective degradation of PCBs by the microorganism
The authors thank the Comunidad Autónoma de Madrid (Spain) for projects 07 M/0640/1997 and 07 M/0049/1998.