Role of sulfate concentration in dechlorination of 3,4,5-trichlorocatechol by stable enrichment cultures grown with coumarin and flavanone glycones and aglycones

Abstract

Metabolically stable anaerobic enrichment cultures have been obtained from sediment samples contaminated with chlorophenolic compounds. Enrichment was carried out with esculin, esculetin, naringin, naringenin, fraxin, quercetin, and acetate in media with two sulfate concentrations. These cultures were used to examine the O-demethylation of 4,5,6-trichloroguaiacol and the dechlorination of 3,4,5-trichlorocatechol. Whereas O-demethylation was observed in all cultures, the occurrence of dechlorination was significantly more restricted. The presence of the carbohydrate moiety in the cultures enriched with the glycones repressed development of populations which were able to carry out dechlorination. Although sulfate at a concentration of 2 g/liter in the primary enrichments blocked the development of populations able to bring about dechlorination, addition of sulfate at this concentration did not inhibit dechlorination in cultures possessing this capability. Different dichlorocatechol isomers were produced under the various conditions, so that in view of the established resistance of some of these to further dechlorination, the ultimate fate of 3,4,5-trichlorocatechol in the natural environment remains partly unresolved. No enrichment culture containing a low sulfate concentration was able to dechlorinate either 2,4,5-trichlorophenol or 2,4,6-trichlorobenzoate.