Abstract
Biodegradation of 2,4-dichlorophenol (DCP), a microbicide, was studied in soil or in liquid medium. In pure culture of Pseudomonas sp. (DP-4), a DCP-degrader, DCP was degraded in soil only when a large amount (10〜100μg of DCP in terms of carbon content in a test tube containing lg of air-dried soil and 1ml of suspension of DP-4) of DCP was added, while DCP was degraded in liquid medium only when a small amount (0.1-10μg of DCP in a test tube which containing 1ml of suspension of DP-4) of DCP was added. Degradation of DCP was incomplete in soil, and a small amount,3.88〜3.30μg, of DCP remained, while degradation in liquid medium was complete. The numbers of DP-4 remained constant or increased compared with the initial ones, except when a large amount, 30〜100μg, of DCP was added in liquid medium. More than 95% of added DCP in soil was found in the solid phase. Moreover, DCP was degraded in soil by the community of soil-native microorganisms irrespective of the amount, 0.1〜100μg, of DCP added. On the other hand, DCP was degraded by this community in liquid medium only when a small amount of DCP was added. The amount of DCP remaining in soil was much smaller, 0.0082〜2.65μg, than that in pure culture of DP-4. These results suggested that DCP-degraders survived in soil and degraded DCP even when a large amount of DCP was added because the concentration of DCP in the liquid phase was remained low due to the adsorption of DCP in the solid phase. In liquid medium, DCP-degrader degraded DCP only when a small amount of DCP was added due to the lack of adsorption. It was suggested that some of the soil-native microorganisms were able to degrade a lower concentration of DCP than DP-4.
