Método Dinámico -Transferencia de Oxígeno

8/11/2019 Mtodo Dinmico -Transferencia de Oxgeno

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VINTAGE PAPER

Introduction

Fermentation and cell culture are at the heart of drugs andbiologics manufacturing. However, unlike most manufac-turing processes in contemporary electronics or automobileindustries, manufacturing in the biotechnology industry isnot well-defined. Indeed, it has been observed that processesfor manufacturing potato chips are more robust than thosefor proteins. In part, the complexity of living systems isresponsible for this situation. The other part is that tools forprocess monitoring are not as widely available in order to geta better understanding of the complex relationship betweengene expression and environmental factors. In order to obtainconsistent production from bioreactors, it is necessary tocarefully monitor and control the process. Consistent scale-up also requires that bioreactor operation conditions be kept

uniform across different scales. One of the most commonscale-up parameters employed is the volumetric oxygentransfer coefficient, or kLa which essentially is a measureof how much oxygen can be supplied to cells growing in abioreactor. Since oxygen is typically the limiting nutrientdue to its poor aqueous solubility, in general cells grown intwo dissimilar bioreactors (e.g., a shake flask and a stirredtank) but operated at equalkLawill show similar growth andproduct formation kinetics (Gupta and Rao, 2003).

However, until the advent of dissolved oxygen electrodes,measuringkLa was not easy. In contrast to prior methods,the Bandyophadhyay article provided a simple and elegant

means to dynamically measurekLa

(Bandyophadhyay et al.,1967). Only a fast responding dissolved oxygen probewas needed and the technique used was based on a briefinterruption in the air (oxygen) supply to the bioreactorand recording the subsequent dissolved oxygen trace. Thetechnique was rapidly adopted and became textbookmaterial (Pirt, 1975). Several articles followed over the

years to improve on the original method. Fred Heinekenpublished a article that carefully considered the quantitativeeffect of probe response time on the accuracy of the kLa

measurement (Heineken, 1971). A few years later, Hill andRobinson (1974) showed how the simple technique could befurther extended to estimate specific growth rate of the

culture. A further study by Tribe et al. (1995) led toquantitation of the errors resulting in kLa measurements ifprobe response time was accounted for. This entire body ofwork is now being applied to the quantitative determinationofkLain present day bioreactor systems such as bag systems

and minibioreactors that use non-invasive oxygen sensors(Hanson et al., 2009).

Here is what Professor Arthur Humphrey himself had tosay via email about his perspective on the article. He recallsthat Professor Taguchi and I wanted to devise a way tomeasure oxygen transfer rates in small and medium sizedfermenters in order to calculatekLas and then to be able tocorrelate these coefficients with agitation and aeration ratesplus fermenter design. This was in the days before on-linecomputers. He then goes on to say that My motivation forthe concept was that you only needed a fast response oxygenprobe (the MIT group had developed a cheap and easy wayfor students to make these probes) to make the measure-ments. Hence, any laboratory could make oxygen transfer

rate measurements and these could be compared withgrowth rate measurements. In my subsequent visits tovarious biotech labs throughout the worldJapan, China,India, Taiwan, Australia, etc., I was amazed at how manylaboratories were using the technique. After publication atleast two dozen articles appeared refining the theory anddefining its application limits. One of the best follow-uparticles was written by Fred Heineken.

So there it isthis article, by virtue of its impact on thepractice of modern biochemical engineering, is a true classicand is one that continues to stand the test of time as thetechnology for bioreactors and oxygen measurement evolves.

Govind RaoCenter for Advanced Sensor Technology & Department ofChemical and Biochemical EngineeringUniversity of Maryland, Baltimore CountyBaltimore, Maryland

References

Bandyopadhyay B, Humphrey AE, Taguchi H. 1967. Dynamic measure-

ment of the volumetric oxygen transfer coefficient in fermentation

systems. Biotechnol Bioeng 9:533544.Gupta A, Rao G. 2003. A study of oxygen transfer in shake flasks using a

non-invasive oxygen sensor. Biotechnol Bioeng 84:351358.Hanson M, Brorson K, Moreira AR, Rao G. 2009. Comparisons of optically

monitored small-scale stirred tank vessels to optically controlled dis-posable bag bioreactors. Microbial Cell Factories 8:44.

Heineken FG. 1971. Oxygen mass transfer and oxygen respiration rate measure-

ments utilizing fast response oxygen electrodes. Biotechnol Bioeng 13:599618.Hill GA, Robinson CW. 1974. Measurement of aerobic batch culture

maximum specific Growth rate and respiration coefficient using a

dissolved oxygen probe. Biotechnol Bioeng 16:531538.Pirt SJ. 1975. Principles of microbe and cell cultivation. London: Blackwell

Scientific.Tribe LA, Briens CL, Margaritis A. 1995. Determination of the volumetric

mass transfer coefficient (kLa) using the dynamic gas out-gas in

method: Analysis of errors caused by dissolved oxygen probes. Bio-

technol Bioeng 46:388392.

Correspondence to: Govind Rao, Center for Advanced Sensor Technology & Depart-

ment of Chemical and Biochemical Engineering, TRC, UMBC, Baltimore, Maryland

21250; telephone: 410-455-3415; fax: 410-455-1049; e-mail: [email protected]

Published online in Wiley InterScience (www.interscience.wiley.com).

DOI 10.1002/bit.22566

2009 Wiley Periodicals, Inc. Biotechnology and Bioengineering, Vol. 104, No. 5, December 1, 2009 841


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842 Biotechnology and Bioengineering, Vol. 104, No. 5, December 1, 2009


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Bandyopadhyay et al.: Vintage Paper 843

Biotechnology and Bioengineering


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Método Dinámico -Transferencia de Oxígeno

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