Bhat et al.
principle was that the bacteria were free of substrate and air was forced
theȱ topȱ ofȱ aȱ fermentorȱ thereȱ wasȱ anȱ airȱ outflow,ȱ thermometer,ȱ coolingȱ
coils and a system to control and remove the build-up of foam. Studies
revealed that system was very sensitive, and since bacteria were dispersed
in cell death (Mazza and Murooka 2009).
Submerged process could be used for production of vinegar in either a
discontinuous, semi-continuous or continuous system. In discontinuous
system, vinegar was produced in batches where a volume of substrate
was completely unloaded from the fermentor. However semi-continuous
system was most commonly used and required a start-up period.
to desired level, about 40–50% of volume was unloaded, while the vinegar
left behind was used as inoculum for next cycle. Advantage of this system
was that there was a shortened bacterial lag time for growth, resulting in
composition of medium at a state where bacteria were in exponential
growth phase and therefore have their highest growth rate, and produced
a conversion of 8-9% acetic acid in 24-48 hours (Garcia-Garcia et al., 2009).
Typical operation mode in industrial submerged culture was semi-
continuous system which consisted of development of successive
Best temperature for industrial production of 11 to 12% vinegar was kept
upto86°F (30°C). In addition, the concentration of acetic acid produced
wasȱaffectedȱbyȱbacterialȱconditionsȱ(DeȱOryȱ et al., 2004).
Most important feature of submerged fermentation systems was their
to break air bubbles and thus facilitated transfer of oxygen from medium
to bacteria. It was found to be an essential step in order to prevent the
Acetobacter cell death. However, even traditional open vat method could be
run in a semi-continuous fashion and had been used in many parts of the
world (Janssens and Swings 2002).