Which of the following industrial processes depends on the action of enzymes?

Step 1: Analyze the question We need to find the industrial process that relies on enzymes, which are biological catalysts made by living organisms.

Step 2: The concept Enzymes are protein molecules produced by living cells (like yeast and bacteria). They speed up specific reactions. Fermentation is the classic industrial use of enzymes.

Step 3: Evaluate each option

• A. Liquefaction of air: This is a physical process. Air is cooled and compressed until it becomes liquid, then separated by fractional distillation. No enzymes are involved.
• B. Manufacture of soap: This is saponification, where fats or oils are heated with an alkali such as NaOH. It is a chemical reaction driven by the alkali (hydrolysis), not by enzymes.
• C. Brewing of beer: Starch from barley is converted to sugars by amylase (diastase) enzymes during malting and mashing. Then the enzyme zymase in yeast converts the sugar to ethanol and carbon dioxide:

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (catalysed by zymase)

This depends directly on enzymes.

• D. Catalytic cracking: This breaks large hydrocarbon molecules into smaller ones using inorganic catalysts (such as zeolites or alumina-silica) at high temperature. These are not enzymes.

Step 4: Answer The correct option is C. Brewing of beer.

Tip: Link "enzymes" with "fermentation": brewing, wine-making, baking, and yoghurt/cheese production. If a process involves yeast or bacteria, enzymes are at work. Processes using heat, pressure, or metal/inorganic catalysts (like cracking or the Haber process) are not enzyme-based.