Abstract
Continuous production by a complete cell-concentration culture using hollow fiber module was conducted to enhance productivity of vinegar containing 10% (w/v) acetic acid. By preventing the discharge of acetic acid bacteria from the fermentor during the culture with the use of the hollow fiber module, cell concentration at 973 hours was increased to 11.27 g-dry cell/l. During the cultivation, acetic acid and ethanol concentrations could be maintained at ca. 10% (w/v) and 1% (v/v), respectively using an ethanol controller. Acetic acid production rate could be enhanced to 13.0 g-acetic acid/ (l. h) on an average for 708 hours. The production of acetic acid can be divided into two stages: one accompanying the growth of acetic acid bacteria and another accompanying the maintenance, the former contributes to the acetic acid production more than the latter. After 200 hours, the relative ratio of the former and the latter was estimated to be 0.69:0.31. Within the period of from 108 to 708 hours, cell concentrations capable of producing acetic acid accompanying growth and maintenance were estimated to be 0.35 and 1.23 g-dry cell/l, respectively. It has been proved that, in the complete cell-concentration culture, cells making no contribution to the production of acetic acid are accumulated in a large amount in the fermentor with the passage of time.
