In standard or batch cultures, cells are grown in a fixed volume of medium. As they grow, nutrients are consumed and metabolites accumulate. Eventually, cultures may stop growing because of nutrient depletion and accumulation of toxic products. The following procedures may prolong the life of batch cultures:
A. Gradual addition of fresh medium and increasing volume of the culture
B. Replacing a constant fraction with an equal volume of fresh medium
C. Occasional removal of used medium and reducing growth factors in the medium
D. Intermittently adding serum and growth factors to the medium
Which one of the following combinations will ensure healthy growth of cells in culture?

Correct option is A

Correct Answer: (a) A and B
Explanation:
Healthy cell growth in culture requires continuous availability of nutrients and effective dilution or removal of toxic metabolites.
Procedure A represents a fed-batch system, where fresh medium is gradually added, delaying nutrient depletion and reducing toxic buildup.
Procedure B represents continuous or semi-continuous culture (chemostat-like), where used medium is regularly replaced with fresh medium, maintaining stable growth conditions.
Together, A and B ensure sustained nutrient supply and controlled metabolite levels, supporting healthy and prolonged cell growth.
Information Booster
· Fed-batch culture extends the exponential growth phase without washing out cells
· Continuous replacement of medium maintains near-steady-state conditions
· Accumulation of toxic metabolites is a major limiting factor in batch cultures
· Balanced nutrient replenishment is more effective than sporadic supplementation
· Culture longevity depends on both nutrient supply and waste management
Additional knowledge
Option (b) B and C is incorrect because reducing growth factors (C) directly limits cell proliferation even if fresh medium is added
Option (c) C and D is incorrect because reducing growth factors counteracts the benefit of adding serum and growth factors, and waste products are not adequately controlled
Option (d) A and D is incorrect because adding serum and growth factors alone does not remove toxic metabolites; without medium replacement, growth will still eventually decline.