An Overview on the Biological Production of Vinegar

compacting material like beech wood shavings, charcoal or coke (Peppler

and Beaman 1967).

Thefermentationwasmostcommonlyperformedintanksmadeofwoodor

steel, with a volume of 50000–60000 litres. The surface area where bacteria

were exposed to oxygen was increased by a packing material in the tank,

on which the bacteria were immobilised. The mostly used packing was

made of beech wood shavings, over which the liquid was sprayed and

thenȱallowedȱtoȱdripȱthroughȱtoȱtheȱbottomȱofȱtheȱreactorȱandȱtheȱairȱwasȱ

blown in from the lower part to maintain high oxygen availability. The

partlyȱfinishedȱvinegarȱthatȱwasȱaccumulatingȱatȱtheȱbottomȱofȱtheȱtankȱ

was re-circulated to the top again until the desired concentration of acetic

acid was obtained. The process was performed at 27-30°C and a cooling

coil in the tank was used to prevent overheating (Raspor and Goranovic

2008).

There were some disadvantages associated with the generator process like

high risk of clogging due to the cellulose-producing bacterial growth in

the generator, accumulation of dead bacteria and infection with vinegar

eels. Another disadvantage observed was a relatively high loss of ethanol

byȱevaporationȱthatȱmadeȱitȱdifficultȱtoȱproduceȱvinegarȱwithȱhighȱaceticȱ

acid concentration (Tesfaye et al., 2002).

Submerged Fermentation

The most common production method was submerged culture which

improved the general fermentation conditions like aeration, stirring,

heating, etc. As generator culture was slow and expensive, submerged

culture fermentors have been used widely at industrial scales. In this

process, the mash is stirred and aerated frequently and the fermentors

areȱ fittedȱ withȱ aȱ heatȱ exchangerȱ forȱ theȱ maintenanceȱ ofȱ theȱ optimumȱ

temperature during the fermentation process (De Ory et al., 1999).

The most commonly method used for commercial vinegar production is

submerged-culture fermentor wherebacteria are suspended in medium,

inȱ contrastȱ toȱ traditionalȱ andȱ generatorȱ process.ȱ Theȱ firstȱ bioreactorȱ ofȱ

submerged type was Fring´sacetator in early 1950´s, and it was followed

by other patented methods as Cavitator, bubble column fermentor and

Effigasȱturbineȱvinegatorȱ(Tesfayeȱ et al., 2002).

Theȱfermentorȱwasȱnormallyȱmadeȱbyȱstainlessȱsteelȱwithȱseveralȱdifferentȱ

volumes, but most commonly in the range of 10000-40000 litres. Basic

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