Question 2 of 14beginner💡 UnderstandShort Answer2 marks

Give examples to prove that microbes release gases during metabolism.

Correct Answer

Microbes release various gases as metabolic end-products, and the type of gas produced depends upon the microbes and the organic substrates they utilise.

During the fermentation of dough used for making foods like dosa, idli, and bread, the puffed-up appearance is due to the production of CO₂ gas. Baker's yeast (Saccharomyces cerevisiae) is used in bread making. Similarly, in cheese making and production of beverages, the main gas produced is CO₂.

Certain bacteria called methanogens (e.g., Methanobacterium) grow anaerobically on cellulosic material and produce large amounts of methane along with CO₂ and H₂. These bacteria are found in the anaerobic sludge during sewage treatment and in the rumen of cattle.

Exercise: EXERCISES | Q: 2 | (Page 11)
For More Understanding

Explanation

This answer draws from two key sections of the textbook: (1) Section 8.1 'Microbes in Household Products' which describes CO₂ production during fermentation of dough for foods like dosa, idli, and bread using bacteria and yeast; and (2) the 'Biogas' section which explains how methanogens like Methanobacterium produce methane during anaerobic breakdown of cellulosic material in sewage treatment and in cattle rumen. The question specifically asks for EXAMPLES, so citing specific foods, organisms, and gases is essential for full marks.

Solution Steps

  1. Step 1: Identify the concept - microbes release gases as metabolic by-products

  2. Step 2: Provide first example - CO₂ production during fermentation of dough (dosa, idli, bread) by bacteria and yeast

  3. Step 3: Provide second example - methane production by methanogens (Methanobacterium) in anaerobic conditions like sewage sludge and cattle rumen

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