Cometabolic degradation of chlorophenols by a strain of Burkholderia in fed-batch culture

This work deals with the study of mono and dichlorophenols degradation by a strain of Burkholderia isolated from the Santa Alejandrina marsh, Minatitlán, Veracruz, México. This strain also degrades benzene, toluene and xylene and was identified as the N₂-fixing bacteria Burkholderia tropicalis. In addition, the cometabolic degradation of 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP) and 2,6-dichlorophenol (2,6-DCP) was evaluated in batch and fed-batch cultures, using phenol as the primary substrate. This bacterial strain was unable to degrade the highly substituted chlorophenols 2,4,5-TCP, 2,4,6-TCP and pentachlorophenol. Except for 4-CP, the cometabolic degradation of chlorophenols in batch culture was slow and inefficient, but when B. tropicalis was cultivated in fed-batch system, the removal efficiencies obtained were 93% for 2-CP, 95% for 2,6-DCP, 96% for 2,4-DCP and 100% for 4-CP. However, low cell growth yields were obtained in both batch and fed-batch cultures. This could be attributed to the uncoupling action of the aromatic compounds involved and, except for 2,6 DCP, to the accumulation of metabolic by-products.