Effects of acetic acid stress on the activity of acetic acid respiratory chains in Acetobacter pasteurianus

Abstract:

[Objective] To analyze the regularity of the activity of respiratory chains and the transcriptional levels of related genes in Acetobacter pasteurianus under the stress of high acetic acid concentration, A. pasteurianus CICC 20001 and A. pasteurianus ATCC 33445 were studied. [Methods] The biomass, acid production and enzyme activity of the two strains have been analyzed in different initial acetic acid concentrations of 0, 1%, 2% and 3%. Real-time quantitative PCR was used to analyzed changes of relative transcriptional levels of respiratory chains related enzyme synthesis genes in different concentrations. [Results] It was found that acid production capacity of two strains was the strongest when initial acetic acid concentration was 1%; and their average acid production rate reached 0.667 g/(L·h) during 48 hours fermentation. At the same time, enzyme activity levels of ADH (alcohol dehydrogenase) and ALDH (acetaldehyde dehydrogenase) also rise to the highest of 12.01 and 9.77 U/mg on average. And the relative transcriptional level of the respiratory chain related enzyme synthesis genes were also increased compared with initial acid of 0. The enzyme activity and acid production capacity decreased gradually when initial acetic acid concentration increased to 2% and 3%. The adh, cyt bd, cyt o and fapA gene on respiratory chain maintained a relatively high transcriptional level while the transcriptional level of rest genes decreased. [Conclusion] It is identified that under high-intensity acetic acid conditions, the transcriptional level of adh gene is increased spontaneously, which activates the substrate phosphorylation and pump acetic acid out. At the same time, the aldh gene’s expression is inhibited, which causing the reducing of acid production and maintaining rather low concentration of acetic acid. In addition, the level of other efflux enzymes in the respiratory chain will also increase, such as cyt bd and cyt o, which enhance the substrate phosphorylation in metabolic process and accelerate the release of energy.