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BACKGROUND Ionic liquids (ILs) have become increasingly attractive as alternatives for organic solvents. In this study, the influences of ILs on the cellular growth rate, cellular activity, cortisone acetate (CA) conversion, CA solubility, and cell membrane permeability of Arthrobacter simplex CPCC 140451 ( ASP) were examined. RESULTS Results showed that ILs with ≥3 carbon atoms in their side chains increased CA conversion, CA solubility, and cell membrane permeability of ASP and universally inhibited the cellular growth rate and activity, with ILs with [PF6]-anion exhibiting the most severe inhibition activity. Inhibition was also more serious using ILs with longer alkyl side chains and at higher concentrations. CA conversion, CA solubility, and leakage of cell inclusions showed higher increase under ILs with [PF6]-anion than those of ILs with [BF4]-anion and lower increase for ILs with longer side chains. CONCLUSION This study improved the understanding of the influence and primary selection of imidazolium-based ILs when applied in steroid biotransformation with Arthrobacter simplex whole cells. The data provided a foundation for the selection of suitable ILs for various applications. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Hydroxypropyl-β-cyclodextrin (HP-β-CD) enhances steroid 1-dehydrogenation biotransformation by Arthrobacter simplex. In this work, HP-β-CD-induced improvement of A. simplex CPCC 140451 cell envelope permeability which had positive effects on the steroid bioconversion was confirmed by a comparative investigation which showed a lower dehydrogenase activity and higher cell permeability of the cells after being incubated with HP-β-CD. Atomic force microscopy and transmission electron microscopy micrographs showed that HP-β-CD altered the size, sharpness, and surface structure of the cell envelope. The analysis of lipid composition revealed that the proportion of extractable lipids decreased and the fatty acids profile was considerably altered. The contents of unsaturated fatty acids and long-chain fatty acids were reduced by 11.77 and 14.98 %, respectively. The total leakage of protein level increased to 8 %. Proteins belonging to the ATP-binding cassette superfamily and major facilitator superfamily were observed outside the cell. These alterations can explain the change of permeability on the molecular level under HP-β-CD treatment. Results showed the material basis and mechanisms underlying the cellular changes, thus most likely contributing to the conversion rate in addition to cyclodextrins known effects on substrate solubility. [ABSTRACT FROM AUTHOR]