Question

What is the purpose of a fed-batch culture in bioprocess technology?

• A. To feed the cells with nutrients continuously
• B. To maintain a constant volume of the culture
• C. To induce stress on the cells
• D. To stop the bioprocess abruptly

Hint:

• Batch culture Closed system, initial nutrients, no addition/removal during run (except gas).
• Fed-batch culture Nutrients are added during cultivation, volume usually increases, product harvested at end.
• Continuous culture (e.g., chemostat) Fresh medium continuously added, and culture (with cells and products) continuously removed to maintain constant volume and steady state.
• Fed-batch is used to achieve high cell densities, prolong production, or control substrate levels.

Answer 1

The Correct Option is A

Fed-batch culture is a biotechnological process where, after an initial batch phase, one or more nutrients (substrates) are fed (either intermittently or continuously) to the bioreactor, while the products remain in the reactor until the end of the run. The volume of the culture typically increases over time due to the feed addition. The main purposes of a fed-batch culture strategy include:

• Prolonging the productive phase of cells: By supplying limiting nutrients, cell growth and/or product formation can be extended beyond what is possible in a simple batch culture where nutrients deplete and waste products accumulate.
• Controlling substrate concentration: Feeding can maintain substrate concentration at an optimal level, avoiding substrate inhibition (if substrate is toxic at high concentrations) or catabolite repression.
• Achieving high cell densities and product yields: By extending the growth/production phase and managing nutrient levels, higher overall productivity can often be achieved.
• Overcoming limitations of batch culture: Such as nutrient depletion, accumulation of toxic byproducts (though fed-batch does not remove byproducts, it can manage their formation rate relative to cell mass).

Let's analyze the options: (a) "To feed the cells with nutrients continuously" (or intermittently): This is a core aspect of fed-batch operation, aiming to supply nutrients to sustain or enhance cell activity. This is TRUE. (b) "To maintain a constant volume of the culture": This is generally FALSE. In fed-batch, volume usually increases as feed is added. Constant volume is a characteristic of a chemostat (continuous culture with outflow). (c) "To induce stress on the cells": While some bioprocesses might use controlled stress to induce product formation, the primary purpose of fed-batch nutrient feeding is generally to support or optimize growth/production, not primarily to induce stress via nutrient manipulation in a general sense. (d) "To stop the bioprocess abruptly": This is incorrect. Fed-batch aims to extend the process. Option (a) best describes a primary purpose of fed-batch culture. \[ \boxed{\text{To feed the cells with nutrients continuously}} \]