Aerobic degradation of 2,4,6-trichlorophenol by a microbial consortium – selection and characterization of microbial consortium

Abstract.

A microbial consortium that efficiently degrades 2,4,6-TCP (2,4,6-trichlorophenol), as the sole source of carbon and energy under aerobic conditions was selected from municipal activated sludge. Six bacterial strains, designated S₁, S₂, S₃, S₄, S₅ and S₆, were isolated from the selected consortium and five were identified as Sphingomonas paucimobilis (S₂, S₃), Burkholderia cepacia (S₄), Chryseomonas luteola (S₅) and Vibrio metschnikovii (S₆). After prolonged cultivation followed by successive transfers, the consortium's degradation ability was improved and reached a specific degradation rate of 34 mg 2,4,6-TCP g^–1 dry weight h^–1 (about 51 mg 2,4,6-TCP g^–1 cell protein h^–1). The soluble chemical oxygen demand, chloride and oxygen uptake balance data clearly indicate the complete dechlorination and mineralization of 2,4,6-TCP. The consortium's activity was not inhibited by 2,4,6-TCP concentrations ≤400 mg l^–1. The highest specific growth rate (µ _max of 0.01 h^–1) was achieved at 2,4,6-TCP concentration ≤200 mg l^–1, and the inhibition constant (K _i) was 610 mg l^–1 according to the Haldane inhibition kinetic model. An inoculum size up to 120 mg l^–1 cell dry weight is desirable in order to avoid a lag phase and to allow faster degradation of 2,4,6-TCP.