In bioreactor characterization, which standard method(s) can be used to determine the oxygen absorption (transfer) rate in a liquid culture system?

Introduction / Context:
Measuring oxygen transfer is central to aerobic fermentation design and scale-up. Engineers routinely estimate volumetric mass transfer coefficients and oxygen absorption rates using chemical and biological methods. This question reviews the common laboratory/plant techniques you should recognize.

Given Data / Assumptions:

• Well-mixed vessel; dissolved oxygen (DO) probe is available when needed.
• Air or oxygen-enriched gas is sparged; temperature and salinity controlled.
• Biological oxygen uptake may be present or purposely eliminated (chemical method).

Concept / Approach:
The sodium sulfite oxidation test chemically removes oxygen with a well-known stoichiometry, letting you back-calculate transfer rate. The dynamic gassing-out method strips DO to low levels and then tracks the DO rise after re-aeration to estimate kLa and absorption rate. Under steady state with known oxygen uptake rate, direct DO balance can also yield oxygen absorption/transfer rates.

Step-by-Step Solution:

Verification / Alternative check:
Cross-compare estimates from chemical vs. biological methods under identical hydrodynamics; values should agree within experimental error if probe response is accounted for.

Why Other Options Are Wrong:

• Saying only one method works ignores standard practice.
• “None”: contradicts decades of reactor testing methodology.

Common Pitfalls:
Neglecting probe lag, temperature correction, or catalyst presence in sulfite tests; misfitting DO transients.

Final Answer:
All of these.