Remediation potential of bacterial mixed cultures for polychlorinated biphenyls (PCBs) biodegradation

Remediation of polychlorinated biphenyls (PCBs) in minimal mineral water media in the presence of bacterial mixed cultures consisting of several individual strains is proposed. Starting from the fact that the properties and features of bacterial strains in mixed cultures can be supplemented and compensated, two-, three- and seven-membered mixed cultures (MC) were performed. The strains used for the construction of the MC were isolated from the waste canal of a former PCB producer. The highest biodegradation of 70 % of the sum of seven defined PCB congeners was achieved by two-membered MC containing the strains Rhodococcus sp. and Stenotrophomonas maltophilia added in the biomass ratio of 1 : 3 and 3 : 1. PCB biodegradation by a seven-membered MC was lower (58 %) but provided several benefits over the less-membered mixed cultures or the individual strains: similarity to naturally occurring microflora, easier preparation of the inocula, certain and repeatable results. Periodical reinoculation of the water media resulted to PCB biodegradation increase to 65 %. Seven-membered MC was applied to the historically PCB contaminated sediment as well, where a 59 % degradation of the sum of seven PCB congeners was determined.