Submerged culture is very efficient and rapid, a semicontinuous run
normally takes 24–48 h. It does however require far more careful control
than simpler processes. The acetic acid bacteria are very susceptible to
interruptions to the air supply, indicating that, in order to survive
suspended in a medium with a pH of 2.5 and 10–14% acidity, the
bacteria need a constant supply of energy from respiration. A stoppage
of only one minute in a stock with a GK of 11.35 is enough to completely
arrest acetification which will not resume when aeration is resumed.
Another possible cause of fermentation failure in submerged acetifi-
cation is phage infection. The presence of bacteriophage particles has
been demonstrated in disturbed vinegar fermentations both in sub-
merged acetifiers and the quick vinegar process. The performance of
Figure 9.16 The Frings Acetator. A, charging pump; B, aerator and motor; C, alkograph;
D, cooling water value; E, thermostat controlling D; F, rotameter; G, cooling
coil; H, air line; I, air exhaust line; J, defoamer
Reproducted by kind permission of Heinrich Frings GmbH, Bonn
360 Fermented and Microbial Foods