Question

Which growth phase is most important for antibiotic production?

• A. Lag phase
• B. Log phase
• C. Stationary phase
• D. Death phase

Hint:

Remember:
• Primary metabolites \(\rightarrow\) Produced during log phase
• Secondary metabolites (antibiotics) \(\rightarrow\) Produced during stationary phase Examples of secondary metabolites: \[ \text{Penicillin, Streptomycin, Tetracycline} \]

Answer 1

The Correct Option is C

Concept: Microorganisms show different phases of growth in a culture medium:
• Lag phase
• Log (exponential) phase
• Stationary phase
• Death phase Antibiotics are generally classified as secondary metabolites. Secondary metabolites are produced mainly when active growth slows down and nutrients become limited, which occurs during the stationary phase.

Step 1: Understanding antibiotic production in microbial growth. During the log phase: \[ \text{Rapid cell division occurs} \] and microorganisms mainly synthesize primary metabolites such as amino acids and proteins. During the stationary phase: \[ \text{Growth rate} = \text{Death rate} \] and microorganisms begin producing secondary metabolites like:
• Antibiotics
• Pigments
• Toxins Therefore: \[ \boxed{\text{Antibiotic production is maximum during the stationary phase}} \]

Step 2: Eliminating the incorrect options.
• Option (A): Lag phase involves adaptation of microorganisms to the environment.
• Option (B): Log phase is mainly associated with rapid growth and primary metabolite synthesis.
• Option (D): Death phase involves decline in viable cell population and is not suitable for antibiotic production. Hence, the stationary phase is most important for antibiotic production.