Phenol degradation at high salinity by a resuscitated strain Pseudomonas sp. SAS26: kinetics and pathway

Abstract

Exploration of novel salt-tolerant phenol-degrading bacterial strains are often limited by unculturability of functional bacteria, as they are prone to entering a viable but non-culturable (VBNC) state in response to complex stressful environmental conditions. Thus, resuscitating the VBNC bacteria provides a huge microbial source to screen effective degraders for bioaugmentation. In this study, a resuscitated strain Pseudomonas sp. SAS26, which exhibited the highest phenol-degrading ability, was selected to investigate its phenol degradation performance at high salinity. The results indicated that SAS26 was capable of efficiently degrading phenol at NaCl concentrations of 0–30 g/L, with decreased efficiency observed at 40–60 g/L. At 10 g/L NaCl, complete degradation of 1800 mg/L phenol was achieved within 48 h. At a higher NaCl concentration of 30 g/L, SAS26 could fully degrade 1500 mg/L phenol within 60 h, with the highest degradation rate of 0.360 g/(g CDW·h) observed at approximately 24 h. The modeling of phenol degradation at high salinity demonstrated that the Webb model was the most appropriate for describing the degradation kinetics, followed by the Yano and Aiba models. Furthermore, the analysis of the enzyme activities and catA gene expression suggested that SAS26 initially converted phenol to catechol via phenol hydroxylase, and then oxidized catechol by the catalysis of catechol 1,2-dioxygenase via the ortho-cleavage pathway. These results revealed the high-efficient phenol-degrading capability of the resuscitated strain SAS26 at high salinity, which shed light on cultivating effective bio-inoculants for treating high-saline phenolic wastewater.