Background: Nowadays, achieving high strength vinegar fermentation is still important to vinegar producers. And the molecular mechanism of acetic acid production and resistance is hotspot in this area. We disclose and improved by transcriptional analysis and enhancing alcohol respiratory chain (ARC) run of Acetobacter pasteurianus.
Method: A better strain Acetobacter pasteurianus FS2-4 which is improved from HS-1 was got through a combination of modified UV irradiation and nitrous acid mutation after acetic acid shock. Under a batch culture in a 7L fermentor, the bacteria are harvested when OD600 is 1.0. The transcript profile about acetic acid production and resistance of Acetobacter pasterurinaus is examined by qRT-PCR. Twenty genes related to tricarboxylic acid (TCA) cycle, acetic acid production and resistance system are chosen. Based on above analysis, the ARC was chosen to be enhanced to improve the production.
Results: The maximum acetic acid yield of Acetobacter pasteurianus FS2-4 increased 26.6% and the initial acidity tolerance increased from 20g/l to 50 g/l. The transcriptional result shows that acetic acid produciton and resistance system is up regulagted while TCA cycle is down regulated. Among acid resistance systems, it shows kdpA, clpB, ompA are enhanced and fapA,B, frbC, purE are down regulated while aatA, Gro EL, Gro ES aren’t changed. Except suc B, all other gene in TCA cycle are down regulated. And we also found acetification rate showed strong positive correlation with ARC activity. So, activity of ARC enzymes, ubiquinone biosynthesis and oxygen availability were taken into account to improve ARC run. Results disclosed that acetification could not be fully inspired until the above three aspects being balanced properly. Therefore, to achieve high strength fermentation, some precursors of alcohol respiration associated factors were added along with an appropriate aeration rate for repeated batches. Obviously, average acetification rate was enhanced to 2.21±0.02 g/L/h with the optimized method, while the original rate was only 1.78±0.02 g/L/h.
This work was supported by a grants from National Natural Science Foundation of China (No. 31301540), the National High Technology Research and Development Program of China (863 Program) (No. 2012AA021201).