Screening Ethanol Tolerance Acetobacter Pasteurianus And Its Mechanism Of Tolerance

The fermentation performance of acetic acid bacteria, which is tightly related to acetic acid productivity and production cost, is affected by many environmental factors such as the concentration of ethanol, acetic acid and adverse temperature. Therefore, ethanol as the substrate of acetic acid fermentation, not only affect the acetic acid productivity, but also the viability of acetic acid bacteria. In the present study, an ethanol tolerance strain was obtained by atmospheric room temperature plasma (ARTP). Then the possible ethanol tolerance mechanism was studied by fermentation properties, membrane permeability, trehalose content, intracellular metabolite and cell membrane fatty acids composition.Firstly, an ethanol tolerance strain T3-06 was obtained through ARTP. The production of acetic acid was 33.38±2.73 g/L with 11%(v/v) ethanol, which was 380.98% higher than the starting strain AP1.01. The analysis of cell membrane permeability and trehalose of strain T3-06 and API.01 showed that the cell membrane permeability of T3-06 with higher trehalose concentration was less than AP1.01. Cell membrane permeability and trehalose content may influence the ethanol tolerance.The study showed that ethanol stress mainly caused the changes of metabolites involved in carbohydrates, lipids and amino acids. EMP and TCA were inhibited under ethanol stress condition. As the result, the carbon metabolic flow of T3-06 was turned to ethanol oxidation, so that the cell could have enough energy to protect itself from environmental stress. The synthesis of protective substances such as proline, leucine and trehalose might confer ethanol tolerance to T3-06.Ethanol repressed the synthesis of saturated fatty acids and increased unsaturated fatty acids, as the result, the SFA/UFA decreased and the membrane fluidity increased. Meanwhile, DPH fluorescent probe assay also verified the changes in membrane fluidity. T3-06 could effectively adjust its fatty acid synthesis then decreased the increase of membrane fluidity under the stress of ethanol. The changes of fatty acids mainly involved hexadecanoic acid, octadecanoic acid and linoleic acid.In conclusion, T3-06 could keep efficient ethanol oxidation capacity, which the activity of ADH and ALDH play an important role under high ethanol concentration, and effectively regulated the carbon, lipid and amino acid metabolism, adjusted membrane fatty acids composition to maintain cell membrane mobility and synthesised protective substance.