Zymomonas mobilis

Zymomonas is an unwanted waterborn bacteria in beer, creating an estery-sulfury flavor due to the production of acetaldehyde and hydrogen sulfide.

Zymomonas have not been reported in lager breweries due to the low temperatures (8–12 °C) and stringent carbohydrate requirements (able to ferment only sucrose, glucose, and fructose).

Unlike E. coli and yeast, Z. mobilis cannot tolerate toxic inhibitors present in lignocellulosic hydrolysates such as acetic acid and various phenolic compounds.

National Renewable Energy Laboratory (NREL), in the United States has made significant contributions in expanding its substrate range to include C5 sugars like xylose and arabinose.

[6][7] Acetic acid resistant strains of Z. mobilis have been developed by rational metabolic engineering efforts, mutagenesis techniques [8] or adaptive mutation.

[9][10] However, when these engineered strains metabolize mixed sugars in presence of inhibitors, the yield and productivity are much lower, thus preventing their industrial application.