Investigating CGTase-Synthesized Cyclodextrins and Environmental Microorganisms for Bioremediation of PCBs

摘要

This study investigated the ability of environmental microorganisms and Bacillus glucanotransferase (CGTase)-synthesized cyclodextrin to enhance the biodegra-dation of polychlorinated biphenyls (PCBs). The microorganism Bacillus circulans is used to produce the CGTase, which in turn is a catalyst in the formation of cyclodextrins from starch. The cyclodextrins (CDs) produced were employed as the bioremediation enhancer. The highest yield of cyclodextrin formed using CGTase generated by B. circulans was observed with a 1% (w/v) starch solution adjusted to pH 10. Using these conditions, approximately 1,040 mg/L of cyclodextrins, in the form of P-CD, was produced by the CGTase. Incubation of PCBs and the starch suspension in the presence of the CGTase demonstrated an appreciable degradation in PCBs as the incubation time increased. It was concluded that during incubation the interaction between the cyclodextrin included PCBs and the microorganisms appeared to have a positive effect on the degradation of PCBs. The results obtained by gas chromatography-mass spectrometry (GC-MS) showed that the biodegradation process conducted over a six-week incubation period had resulted in a considerable decrease in total PCBs. It was also noted that contacting PCBs with cyclodextrins significantly increased the solubility of PCBs in water and changed the PCB congener pattern (i.e., ratios of adjacent peak heights).