AimsTo evaluate the comparative impact of high initial concentrations of acetic acid (AA(i)) and of ethanol (ETi) on acetification rate (ETA). Methods and ResultsAcetic acid bacteria (AAB) were cultivated in a 100-l internal Venturi injector bioreactor. To quantify the oxygen availability, the 10lmin(-1) air inflow rate for the start-up phase (25l) while 30lmin(-1) for the operational phase (75l) achieved a high oxygen transfer coefficient (k(L)a). Changes in cell wall by TEM images and the remained ADH and ALDH activities confirmed the high acid tolerance ability of AAB. While ETAs using high AA(i) at 65gl(-1) could be processed of 957019gl(-1)day(-1), which is just higher than 912012gl(-1)day(-1) using high ETi at 55gl(-1). The average biotransformation yields were at 963 +/- 01% and 944 +/- 01% for high AA(i) and ETi, respectively. ConclusionsResults confirm that high oxygenation was generated in the bioreactor. Both high AA(i) and ETi were important in increasing ETA under stress 100gl(-1) total concentration. Significance and Impact of the StudyHigh acid-tolerant AAB contains the high ADH and ALDH activities causing higher ETAs in HIA process. It is a competitive commercialized acetification process.