Continuous culture definitions — An open system where growth rate is controlled by feeding a limiting nutrient at the same rate that culture is withdrawn is called what?

Introduction:
Continuous culture systems maintain cells in a defined physiological state for extended periods. This question distinguishes the chemostat from other control modes by focusing on limiting-nutrient feed and matching effluent withdrawal.

Given Data / Assumptions:

• Perfect mixing; constant volume.
• Single limiting nutrient in feed controls mu.
• Effluent removal rate equals feed rate (dilution rate D).

Concept / Approach:
In a chemostat, mu = D at steady state, set by the concentration of the limiting nutrient in the feed and the chosen flow rate. This differs from a turbidostat, which controls biomass via turbidity feedback, and perfusion systems, which retain cells using filters or settlers.

Step-by-Step Solution:
1) Identify control variable: limiting nutrient in the feed.2) Recognize mass balance: F_in = F_out keeps volume constant; D = F/V.3) At steady state, mu adjusts to equal D given substrate limitation; biomass remains approximately constant.

Verification / Alternative check:
Steady-state equations predict X and S as functions of D and feed substrate; laboratory chemostats confirm stable operation at fixed D below mu_max.

Why Other Options Are Wrong:

• (a) Manostat is not the standard term for this configuration.
• (c) Turbidostat maintains constant turbidity with feedback, not fixed limiting nutrient.
• (d) Culturostat is a nonstandard/rarely used term in this context.
• (e) Perfusion retains cells and decouples residence time of cells from medium, unlike a classical chemostat.

Common Pitfalls:
Confusing chemostat (nutrient-limited) with turbidostat (biomass-controlled); ignoring washout limits when D approaches mu_max.

Final Answer:
Chemostat