The mycelium growth and enzyme activity of Aspergillus niger C2J6 in organic solvent are related to cell tolerance in the solvent. In order to reveal the regulation and mechanism of organic solvent tolerance

fifteen kinds of organic solvents were used to investigate the organic solvent tolerance of Aspergillus niger C2J6. Then the tolerance mechanism for cyclohexanone

which is a less hydrophobic solvent

was studied in the cellular level. The results indicate that Aspergillus niger C2J6 can grow in a variety of organic solvents for enzyme production. Organic solvents whose lgP are between -0.24 and 3.0 will inhibit the cell growth and enzyme production to different degrees

whereas organic solvents whose lgP are greater than 3.0 will promote the growth and production. Under the stress of cyclohexanone

the cell membrane is damaged. The intracellular organelles shrunk. The hydrophobicity of cell surface decreased. Extracellular nucleotide concentration increased. The content of unsaturated fatty acid decreased while the content of saturated fatty acid increased. These phenomena illustrate that cellular tolerance to cyclohexanone is influenced in many aspects

and there are variety of tolerance mechanisms working together which help to reduce the toxicity of cyclohexanone on the cells

so as to improve the tolerance of the microbes.