|MadSci Network: Microbiology|
Almost all food materials contain some amount of microorganisms like bacteria and/or fungi. All food materials also contain nutrients, including sugars, which many fungi and bacteria can metabolize to obtain energy. Byproducts that result from this metabolism include various gasses, of which carbon dioxide is usually the most common. The higher the sugar content, the more gas you can usually get. Any food microbiology text book would be a good resource for more details on microbial metabolism (look for definitions of aerobic respiration and fermentation). Note the factors that affect the rates of these reactions like redox potential, pH, and temperature to name a few.
These websites might get you started in the right direction to learn more about nutrient metabolism by microoganisms:
Hope that helps.
Moderator's Note: Anaerobic metabolism of certain sugars, amino acids and other compounds can also lead to the production of methane gas (CH4) and hydrogen gas (H2). Other organisms are also able to denitrify nitrates (NO3) and nitrites (NO2) all the way to release nitrogen gas (N2).
Try the links in the MadSci Library for more information on Microbiology.