The examples of bacteria that release gases during metabolism are:

Bacteria and fungi carry out the process of fermentation and during this process, they release carbon dioxide. Fermentation is the process of converting a complex organic substance into a simpler substance with the action of bacteria or yeast. Fermentation of sugar produces alcohol with the release of carbon dioxide and very little energy.

$Glu\cos e\xrightarrow[{oxygen}]{{Without}}alcohol + energy + C{O_2}$

The dough used for making idli and dosa gives a puffed appearance. This is because of the action of bacteria which releases carbon dioxide. This $\mathrm{CO}_{2}$ released from the dough gets trapped in the dough, thereby giving it a puffed appearance.