Methods in Molecular Biology (2022) 2436: 17–25

DOI 10.1007/7651_2021_415

© Springer Science+Business Media, LLC 2021

Published online: 10 August 2021

Volumetric Mass Transfer Coefficient Measurement in a

Stirred Tank Reactor

Aysegul Inam, Ezgi Rojda Taymaz, Mehmet Emin Uslu, Baris Binay,

and Irem Deniz

Abstract

A bioreactor is a controlled vessel which provides biological conversions into bioactive components using

cells or enzymes. In the aerobic processes, it is important to know oxygen requirements of the cells which

may vary during fermentation as a result of microbial activity, aging, substrate depletion and product

formation, etc. Here we describe the measurement of volumetric mass transfer coefficient (kLa) in a stirred

tank reactor using dynamic method based on unsteady state which is also one of the significant parameter

especially in scaling-up. The equipment in the measurement according to dynamic method has low cost

compared to steady-state methodology. This method is reliable in the determination of kLa when the gas

residence time and probe measuring the oxygen concentration of response time are in specific requirements.

Key words Aerobic processes, Dissolved oxygen concentration, Dynamic method, Stirred tank reac-

tor, Volumetric mass transfer coefficient

1

Introduction

Gas transfer is defined as the process in which gas moves from one

phase to another. This phenomenon is used in mass transfer and

oxygen transfer for the continuity of biological processes during

bioproduction in bioreactors. The transition of oxygen from gas

phase to liquid phase is crucial for aerobic process especially for:

enzyme production, biomass related product formation, wastewa-

ter treatment, and animal cell cultures [1].

Aerobic microorganisms in fermentation broth produce the

energy required for their survival and growth by using dissolved

oxygen molecules. Oxygen, like all gases in the atmosphere, dis-

solve in water

to a certain degree [2]. Dissolved oxygen

(DO) concentration is highly depended on temperature, pressure,

and salinity level of the water. Maximum DO concentration at

1 atm and room temperature is 8.26 mg/L for pure water [3].

In bioprocesses where aerobic microorganisms are involved, it

is very important to maintain the desired level of DO concentration

in the fermentation broth [4]. Several organisms need very high

17