Question

A common concern for beer brewers making sour beers is contamination from Acetobacter. This organism converts ethanol to acetic acid and gives the finished product an undesirable vinegar flavor. Which of the following media would serve as a good enrichment medium to detect the presence of Acetobacter in a brewery environment?

a. Carbon dioxide, yeast extract, trace elements
b. Cellulose, phosphate buffer, magnesium sulfate, calcium chloride, trace elements
c. Ethanol, ammonium chloride, phosphate buffer, magnesium sulfate, calcium chloride, trace elements
d. Glucose, ammonium chloride, phosphate buffer, magnesium sulfate, calcium chloride, trace elements

Answer 1

Answer: Option C.

Step-by-step explanation:

Acetobacter is an acetic acid bacteria that convert ethanol to acetic acid in the presence of oxygen. This bacteria oxidize lactate and acetate into carbon dioxide and water. Acetic acid bacteria are found in media that have high concentration of carbohydrates like fruits and ethanol. Acetobacters are found in fermented foods. Ethanol, ammonium chloride, magnesium sulfate, calcium chloride, phosphate buffer and trace elements are good enrichment media for acetobacters growth because of high concentration of sugar.

Answer 2

C. Ethanol, ammonium chloride, phosphate buffer, magnesium sulfate, calcium chloride, trace elements

Step-by-step explanation:

Acetobacter must have a sufficient supply of oxygen and cannot grow in its absence. Colonies of acetobacter can be detected by a culture media containing ethanol as carbon source, the acid produce by the bacteria will dissolve the chalk thereby leaving a clear zone around the colony.