Acetic acid bacteria of the genus Acetobacter are used to made acetic acid, in t
ID: 789641 • Letter: A
Question
Acetic acid bacteria of the genus Acetobacter are used to made acetic acid, in the form of vinegar. Given sufficient oxygen, these bacteria can produce vinegar from a variety of alcoholic foodstuffs. Commonly used feeds include apple cider, wine, and fermented grain, malt, rice, or potato mashes. The overall chemical reaction facilitated by these bacteria is:
C2H5OH + O2 ? CH3COOH + H2O
One of the first modern commercial processes was the "German method", first practised in Germany in 1823. In this process, fermentation takes place in a tower packed with wood shavings (where the bacteria reside). The alcohol-containing feed is trickled into the top of the tower, and fresh air supplied from the bottom. The aqueous solution collected at the bottom is the desired product.
If we start with 1000L of wine (14% wt/vol of ethanol in water), what is the maximum concentration (wt/vol) of acetic acid that we can possibly obtain? What is the minimum volume of air (containing 20% by volume of O2) at 1atm and 37C that we must we supply to bring about the maximum concentration of acetic acid in the product.
Please show your work
Explanation / Answer
ethanol mass = 14 gm per 100 ml wine
hence 1000 liters = 1000 x 1000 ml wine contains = 10^6 x 14/100 = 140000
ethanol moles = 140,000 /46 = 3043.5
moles of acetic acid = 3043.5 ( as 1 ethanol gives acetic acid)
acetic acid mass = 3043.5 x 60.05 = 182761 gm
conc max of acid =100 x ( 182761 ) /(1000 x1000) = 18.276 w/v %
moles of O2 required = 3043.5
vol of O2 = nRT/P = 3043.5 x 0.0821 x 310/1 = 77460 liters
vol of air required = ( 100/20) x ( 77460) = 387300 liters