Degradation of 3-chlorobenzoate and phenol singly and in mixture by a mixed culture of two ortho-pathway-following Pseudomonas strains

Abstract

The compatibility and efficiency of two ortho-cleavage pathway-following pseudomonads viz. the 3-chlorobenzoate (3-CBA)-degrader, Pseudomonas aeruginosa 3mT (3mT) and the phenol-degrader, P. stutzeri SPC-2 (SPC-2) in a mixed culture for the degradation of these substrates singly and simultaneously in mixtures was studied. Another phenol-degrading strain, Pseudomonas sp. SoPC-5 (SoPC-5) that utilizes a meta-cleavage mode also was tried in co-culture with 3mT. The former combination was found to be a better degrader of both the substrates when present alone. But, with inoculum levels of 0.15 mg cell dry wt each of 3mT/SPC-2 or 3mT/SoPC-5 growth with 2 mM each of 3-CBA and phenol was slow with a lag of 24 h and degradation being incomplete. However, with higher inocula in the ratios 1:1, 1:2, and 2:1, i.e., 0.3 + 0.3, 0.3 + 0.6, and 0.6 + 0.3 mg cell dry wt of 3mT and SPC-2, respectively complete degradation of both the substrates occurred. Degradation of 3-CBA was complete with the release of stoichiometric amounts of chloride (Cl(-)) when concentrations of phenol/3-CBA were varied as 2:2, 2:4, and 4:2 mM, i.e., even when the concentration of the more toxic co-substrate 3-CBA was higher than phenol effective simultaneous degradation occurred at the inoculums ratio of 1:1 (0.3 mg dry cell wt. of each strain). These studies clearly indicated the better suitability of ortho-cleavage-utilizing strains as partners in a mixed culture than those follow different modes.

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

“…Such a phenomenon of reaching the adsorption/biosorption equilibrium at early hours of incubation has been demonstrated in several cases (Aksu, 2005). In our previous studies on simultaneous degradation of phenol/3-CBA mixture by a mixed culture of free cells of strains of SPC-2 and 3mT in shake flasks also such a phenomenon was observed (Jayachandran and Kunhi, 2009). …”

“…CP4 (Babu et al, 1995b;Ahamad and Kunhi, 1999;Ahamad et al, 2001) and Pseudomonas aeruginosa 3mT (Babu et al, 1995a;Ajith-Kumar and Kunhi, 2000;Jayachandran and Kunhi, 2009) used in this study were the ones isolated in the laboratory previously.…”

“…at a flow rate of 1 ml/min and was detected by UV absorbance at 235/275 nm (Jayachandran and Kunhi, 2009). …”

“…Inorganic chloride (Cl¯) released to the medium was estimated by the procedure of Bergmann and Sanik (1957) based on the principle of displacement of thiocyanate ion from mercuric thiocyanate by chloride ion, in the presence of ferric ion, as described by Jayachandran and Kunhi (2009).…”

“…strain CP4 (CP4), which could degrade up to 1.5 g/L of phenol (Babu et al, 1995b) and up to 2.0 g/L of cresols (Ahamad and Kunhi, 1999;Ahamad et al, 2001) through meta-cleavage pathways and P. aeruginosa strain 3mT (3mT) capable of degrading 8.0 g/L of 3-CBA and 12 g/L of 4-chlorobenzoate (4-CBA) via a modified ortho-pathway (Ajith-Kumar and Kunhi, 2000). A mixed culture of the strain 3mT and an ortho-pathway-following phenol degrader, Pseudomonas stutzeri strain SPC-2 (Ahamad and Kunhi, 1996) also degraded 3-CBA-phenol mixtures efficiently when used as free suspended cells in shake flasks (Jayachandran and Kunhi, 2009).…”