Fungi and bactaria can breakdown organic compounds using fermentation. They release CO₂ during this process. Common examples which show microbes release gases are:

• Dough of idli and dosa gives puffed up appearance because of release of CO₂ during the process of fermentation by bactaria.

• Dough of bread is puffed up because of fermatation by Saccharomyces cerevisiae.

• The large holes in Swiss cheese are caused due to production of a large amount of CO₂ during fermentation by a bacterium named Propionibacterium sharmanii.