Mycobacterium sp., Rhodococcus erythropolis, and Pseudomonas putida behavior in the presence of organic solvents

This work aimed at studying the behavior and tolerance of Mycobacterium sp. NRRL B-3805, Rhodococcus erythropolis DCL14 and Pseudomonas putida S12 cells in the presence of various concentrations of water miscible (ethanol, butanol, and dimethylformamide, up to 50% v/v) and water immiscible solvents (dodecane, bis(2-ethylhexyl) phthalate and toluene, up to 5% v/v). When incubated in the presence of these solvents, the cells were found to have lower tolerance to butanol and toluene than to the remaining solvents. Nevertheless, the concentrations of solvents endured by the tested strains show that they are quite solvent-tolerant, confirming their potential as biocatalysts in nonconventional systems. Microscopic observation of samples showed that the hydrophobic Mycobacterium sp. and R. erythropolis cells were able to aggregate to protect the population under stress conditions. Comparison of the results obtained at the single cell level by fluorescence microscopy and colony development on agar plates indicated that the primary effects of most solvents tested were on the cell membrane and replicating capability of the cells.