Fermentation rate and fermentation efficiency are two key aspects for industrial vinegar production. A new target, ratio of oxygen consumption versus acid yield, is introduced to evaluate the fermentation efficiency. Semi-continuous fermentation is optimized by means of harmony between acetification rate and ratio of oxygen consumption versus acid yield. This protocol operates on initial acidity of discontinuous procedure to adjust bacterial metabolism which directly affects the fermentation process. As a result, average acetification rate is increased to 1.81 g acid/I h, which is 20% higher than the original level (1.48 +/- 0.32 g acid/I h), and the air flow rate is also reduced by 41% of initial setting. In such a condition, the stoichiometry yield of vinegar is also improved to 94.3 +/- 0.67%. So this method could be considered to optimize the industrial scale process in future. (C) 2013 Elsevier Ltd. All rights reserved.