Drastic change in cell surface hydrophobicity of a new bacterial strain, Pseudomonas sp. TIS1-127, induced by growth temperature and its effects on the toluene-conversion rate

In a previous study, we reported the effectiveness of a bacterial strain showing monolayer adsorption to oil surfaces on microbial conversion at oil–water interfaces. In the present study, we screened wild type strains from our toluene-degrading bacterial library that showed similar properties and succeeded in obtaining five wild type strains that adsorb to oil surfaces as a cell monolayer. We investigated the effects of cultivation conditions on cell surface hydrophobicity of these five strains. The effects of substrate hydrophobicity and the porous carrier were not significant. By contrast, growth temperature greatly affected the cell surface hydrophobicity of all five strains, especially strain TIS1-127, which was phylogenetically identified as Pseudomonas sp. which is closely related to P. mosselii, P. monteilii, and P. plecoglossicida. Pseudomonas sp. TIS1-127 cells grown at 37 °C were determined by the kinetic microbial-adhesion-to-hydrocarbon (MATH) test to be fully hydrophilic (lower than 10% of MATH value) while the cells grown at 28 °C were highly hydrophobic (over 90% of MATH value). We investigated the effects of growth temperature on toluene conversion by TIS1-127 resting cells in single-phase batch cultivation and in two-liquid-phase partitioning reactors containing an emulsion consisting of 20% silicone oil and 80% cell suspension. In both cases, the cells grown at 28 °C showed much higher conversion ability than those grown at 37 °C. Toluene conversion followed Michaelis–Menten kinetics and the Km values for the cells grown at 28 °C were lower than 1/10 those for the cells grown at 37 °C.