Abstract: The enhancing effect of low concentrations of exogenous acetic acid on the fermentation of acetic acid by Acetobacter pasteurianus CICC 20001 was evaluated, and the underlying molecular mechanism was investigated using transcriptomics. The results showed that the acid production efficiency was significantly improved by addition of 0.5% acetic acid to the culture medium. A total of 482 significantly differentially expressed genes between the fermentations with and without 0.5% acetic acid were identified, of which 424 were up-regulated and 58 were down-regulated. In total 412 and 70 significantly differentially expressed genes were observed on days 1 and 7 of fermentation, respectively. Addition of 0.5% acetic acid to the culture medium could enhance the tolerance of A. pasteurianus to acetic acid by urea metabolism, propionic acid metabolism and acetic acid assimilation metabolism, reduce the toxic effect of acetic acid on the bacterium, and ultimately improve the acid production efficiency. In addition, strengthening the signal transduction, membrane transport and energy metabolism in A. pasteurianus may be important for nutrient transport and energy transformation in acetic acid fermentation. These results will provide new insights into the mechanism by which exogenous acetic acid enhances acid production by A. pasteurianus and provide a theoretical basis for improving the efficiency of acetic acid fermentation.

Key words: Acetobacter pasteurianus; transcriptomics; acetic acid fermentation; exogenous acid; differentially expressed genes