Abstract
We investigated the effects of the presence of four duckweeds, Spirodela polyrhiza, Lemna minor, Lemna aequinoctialis, and Wolffia arrhiza, on phenol removal from environmental waters. Phenol was more rapidly removed from water with duckweeds than without duckweeds. In contrast, phenol concentrations did not decrease in autoclaved Hoagland solutions with sterilized duckweeds. These results indicated that all the duckweeds could mediate the acceleration of phenol removal from water and that the acceleration was not caused by phenol uptake by the duckweeds. S. polyrhiza and W. arrhiza were associated with the greatest acceleration of phenol removal. A variety of phenol-degrading bacteria, including Pseudomonas spp., Delftia spp., Azospirillum spp., Acinetobacter spp., and Zoogloea spp., were isolated from S. polyrhiza and W. arrhiza. Extracts from the duckweed plants promoted the cell growth and/or rate of phenol degradation by the bacterial isolates. These results suggest that duckweeds can provide a habitat for phenol-degrading bacteria, stimulate their growth, and enhance their phenol-degradation activity. The results of this study have helped to identify duckweed species best suited for treatment of phenol-polluted waters.
