Abstract
Continuous production by a partial discharging of cell-concentration broth using hollow fiber module was conducted to enhance productivity of vinegar containing 10% (w/v) of acetic acid and to suppress the excessive increase in the cell concentration. By discharging of some portion of cells from the fermentor, the cell concentration C. (g-dry cell/l) in it was expressed as the function of discharged ratio θ(=Fx/F;Fx and F are the discharging rate of cell-concentration broth and the feeding rate of medium, respectively.), which indicated that the cell concentration could be regulated by controlling the discharged ratio.
Cx=0.117(1/θ)+0.0551
The maximum acetic acid production rate of 16.6 g-acetic acid/l·h) could be attained at the dilution rate of 0.163 h-1 and the discharged ratio of 0.1. The high growth rate contributed to the achievement of high production rate of acetic acid. Continuous fermentation was conducted at a dilution rate of 0.077 h-1 and a discharged ratio of 0.2 for 80 days. Thus a vinegar, which contained 105.1 g-acetic acid/l and 4.5 g-ethanol/l could be constantly produced at an average acetic acid production rate of 8.1 g-acetic acid/(l·h) and at a yield of 0.95 g-acetic acid/1.304 g-consumed ethanol.
