The influence of physicochemical effects on the microbial degradation of chlorinated biphenyls

The influence of different forms of substrate administration (either through the vapour phase or the liquid phase) on growth of two bacterial strains on biphenyl, 2-chlorobiphenyl, and 3,5-dichlorobiphenyl has been investigated. During growth with all three compounds, the availability of the substrate for the cells turned out to be the growth-limiting factor, even in liquid culture with excess substrate supplied to the medium. Growth on biphenyl and 2-chlorobiphenyl could be greatly enhanced if the substrate was distributed on a folded filter providing a large surface, which was placed in the vapour phase of the culture flask. This was not possible in the case of 3,5-dichlorobiphenyl. Here growth accelerated after accumulation of a yellow meta cleavage product. Through measurement of the surface tension it was shown that this yellow compound possessed detergent-like activities, increasing the amount of 3,5-dichlorobiphenyl dissolved in the medium.