Simultaneous degradation of phenol and 3-chlorobenzoate by a mixture of separately immobilized cells of two strains of Pseudomonas – A preliminary study

Simultaneous degradation of halogenated and non-halogenated aromatic compounds that are catabolised through different cleavage pathways is generally difficult due to biochemical incompatibility. However, free cells of a mixed culture of Pseudomonas sp. CP4 that degrades phenol through meta-pathway and Pseudomonas aeruginosa strain 3mT that degrades 3-chlorobenzoate through ortho-pathway was shown, earlier, to degrade mixtures of phenol/cresols and 3-chlorobenzoate in shake flasks. In the present study the degrading efficiency of these strains when immobilized (separately) in Ca-alginate gel beads was tested using a fluidized bed reactor. Complete mineralization of up to 5 mM equimolar mixture of phenol and 3-chlorobenzoate was observed when the beads were used at 1:1 ratio. From a 10 mM equimolar mixture although phenol was completely mineralized 3-chlorobenzoate degradation was not complete as evidenced by accumulation of some intermediary metabolites and the release of only 86% of inorganic chloride (Cl¯). Degradation rates of both the compounds by the immobilized cells, in general, were far better than that by the free cells. With further studies to select suitable gel matrices and optimization of bioreactor conditions these strains can be effectively deployed for treatment of heterogeneous aromatic wastes.