Fermentation is the process by which biomolecules, especially carbohydrates, are broken down anaerobically by enzymes. Obligate and facultative organisms use this process as a means of cellular respiration to produce energy (in ATP form).
In the diagram, it can be viewed that yeat easily breaks down glucose compared to sucrose hence produces more carbon (IV) oxide bubble in the breakdown of the former than latter. It is important to note that carbon dioxide is a product of fermentation of carbohydrates. Alcohol ,such as ethanol, is the other product.
When yeast is boiled, it is killed hence cannot carry out fermentation. This is why boiled yeast does do not produce bubbles when mixed with the disaccharides.
