Impact of high initial concentrations of acetic acid and ethanol on acetification rate in an internal Venturi injector bioreactor

Abstract

Aims: To evaluate the comparative impact of high initial concentrations of acetic acid (AAi) and of ethanol (ETi) on acetification rate (ETA). Methods and Results: Acetic acid bacteria (AAB) were cultivated in a 100-l internal Venturi injector bioreactor. To quantify the oxygen availability, the 1·0 l min-1 air inflow rate for the start-up phase (25 l) while 3·0 l min-1 for the operational phase (75 l) achieved a high oxygen transfer coefficient (kLa). 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 AAi at 65 g l-1 could be processed of 9·57 ± 0·19 g l-1 day-1, which is just higher than 9·12 ± 0·12 g l-1 day-1 using high ETi at 55 g l-1. The average biotransformation yields were at 96·3 ± 0·1% and 94·4 ± 0·1% for high AAi and ETi, respectively. Conclusions: Results confirm that high oxygenation was generated in the bioreactor. Both high AAi and ETi were important in increasing ETA under stress 100 g l-1 total concentration. Significance and Impact of the Study: High acid-tolerant AAB contains the high ADH and ALDH activities causing higher ETAs in HIA process. It is a competitive commercialized acetification process.