In this study, a water–silicone oil biphasic system was developed to enhance the biodegradation of monochlorobenzene (CB) by Delftia tsuruhatensis LW26. Compared to the single phase, the biphasic system with a suitable silicone oil fraction (v/v) of 20% allowed a 2.5-fold increase in the maximum tolerated CB concentration. The CB inhibition on D. tsuruhatensis LW26 was reduced in the presence of silicone oil, and the electron transport system activity was maintained at high levels even under high CB stress. Adhesion of cells to the water–oil interface at the water side was observed using confocal laser scanning microscopy. Nearly 75% of cells accumulated on the interface, implying that another interfacial substrate uptake pathway prevailed besides that initiated by cells in the aqueous phase. The 8-fold increase in cell surface hydrophobicity upon the addition of 20% (v/v) silicone oil showed that silicone oil modified the surface characteristics of D. tsuruhatensis LW26. The protein/polysaccharide ratio of extracellular polymeric substances (EPS) from D. tsuruhatensis LW26 presented a 3-fold enhancement. These results suggested that silicone oil induced the increase in the protein content of EPS and rendered cells hydrophobic. The resulting hydrophobic cells could adhere on the water–oil interface, improving the mass transfer by direct CB uptake from silicone oil.

A newly isolated strain was identified as Ochrobactrum sp. by 16S rRNA sequence analysis and named as ZJUTCB-1. The strain was able to degrade mono-chlorobenzene (CB) as the sole carbon and energy source under aerobic conditions. This study is the first to report the degradation of CB by the genus Ochrobactrum. The degradation rate of CB reached 170.9 μmol L⁻¹ h⁻¹, which is at least 6 times higher than the previously reported data. The strain can efficiently degrade CB under a rang of temperatures (30–40 °C) and pH (6.0–7.0) with optimum at 40 °C and pH 7.0. Salt concentration higher than 0.05 mol L⁻¹ remarkably reduced the biodegradation capability. Moreover, true oxic condition was not an essential element for biodegradation given that the CB degradation rate of 210.4 μmol L⁻¹ h⁻¹ was obtained under microaerobic condition. Based on the Haldane kinetic model, the maximum specific growth rate was 0.895 h⁻¹, which is the highest in ever described CB-degrading strains. According to GC-MS analysis and enzymatic assay, CB was degraded via the meta-cleavage pathway by using 2,3-dioxygenase and 2-chlorophenol as the main intermediates, producing CO₂ and Cl⁻ as the final products. The great performance of CB degradation by Ochrobactrum sp. ZJUTCB-1 provided an alternative for development of more effective and reliable biotreatment process.

The presence of nicotine and nicotinic acid (NA) in the marine environment has caused great harm to human health and the natural environment. Therefore, there is an urgent need to use efficient and economical methods to remove such pollutants from the environment. In this study, a nicotine and NA-degrading bacterium—strain JQ581—was isolated from sediment from the East China Sea and identified as a member of Pseudomonas putida based on morphology, physio-biochemical characteristics, and 16S rDNA gene analysis. The relationship between growth and nicotine/NA degradation suggested that strain JQ581 was a good candidate for applications in the bioaugmentation treatment of nicotine/NA contamination. The degradation intermediates of nicotine are pseudooxynicotine (PN) and 3-succinoyl-pyridine (SP) based on UV, high performance liquid chromatography, and liquid chromatography-mass spectrometry analyses. However, 6-hydroxy-3-succinoyl-pyridine (HSP) was not detected. NA degradation intermediates were identified as 6-hydroxynicotinic acid (6HNA). The whole genome of strain JQ581 was sequenced and analyzed. Genome sequence analysis revealed that strain JQ581 contained the gene clusters for nicotine and NA degradation. This is the first report where a marine-derived Pseudomonas strain had the ability to degrade nicotine and NA simultaneously.