EPPENDORF_Nov2021_UpstreamBioprocessingImprovingEfficiency - 11

analyzers are two examples for substrate analyzers.
Feeding based on the substrate concentration
allows a particularly close control of one specific
nutrient, in most cases the major carbon source.
3) Feeding based on the respiratory quotient
Principle: The respiratory quotient is the quotient of
carbon dioxide produced and oxygen consumed by a
culture. It specifies which carbon source is primarily
consumed by the culture, expressed as the carbon
dioxide transfer rate (CTR) and the oxygen uptake
rate (OUR). For example:
* Glucose: The RQ for the metabolization of
glucose is 1, because per mol glucose, 6 mol
are needed and 6 mol CO2
are produced.
* Ethanol: As ethanol is more reduced than
glucose, the use of ethanol as substrate results
in a RQ value below 1.
As an example, the RQ in a Pichia pastoris bioprocess
with glucose as the main carbon source could
develop as follows:
If glucose is metabolized, the RQ is 1 (see above).
Once glucose is fully metabolized the culture starts
to consume fermentation by-products. These
by-products mainly consist of ethanol which is
produced under aerobic conditions at high glucose
concentrations in respiro-fermentative yeasts. Therefore,
the RQ drops below 1.
Implementation: To automate feeding based on
How to improve
your bioprocess by
integrating sensors?
the RQ, a script can be implemented in the bioprocess
control software (e.g. DASware control). A drop
of the RQ below 1 indicates glucose depletion and
triggers the initiation of a feed pump. The implementation
of RQ-based feeding is described in detail in
the next article of this eBook.
Sensor: RQ calculation requires information on
the gas led into the bioreactor and the exhaust
composition. The Eppendorf DASGIPĀ® GA exhaust
analyzer provides automatic calculation of oxygen
and carbon dioxide transfer rates (OTR, CTR) and
respiratory quotient as well as feedback control.
We have presented different examples of automated
culture feeding programmed using software scripts.
In the example of time-based feeding, a mathematical
equation was implemented to control culture feeding.
In the example of sensor-based feeding, the control
loop employed external values from integrated
sensors. Scripts can also be used to implement logical
combinations, process staging to separate the process
into different phases, and more. Like this, software
scripts allow for flexible and customized process control.
A Beginner's Guide to Bioprocess Modes - Batch, FedBatch, and Continuous
Fermentation. Ying Yang and Ma Sha. Eppendorf Application Note 408.
GENengnews.com | 11
https://www.eppendorf.com/fileadmin/knowledgebase/asset/OC-en/763594.pdf https://www.eppendorf.com/fileadmin/knowledgebase/asset/OC-en/763594.pdf https://www.eppendorf.com/MY-en/service-support/eppendorf-training-center/webinars/recorded-webinars/recorded-webinar-increasing-upstream-bioprocessing-efficiency-through-process-analytical-technology/ http://www.GENengnews.com


Table of Contents for the Digital Edition of EPPENDORF_Nov2021_UpstreamBioprocessingImprovingEfficiency

EPPENDORF_Nov2021_UpstreamBioprocessingImprovingEfficiency - 1
EPPENDORF_Nov2021_UpstreamBioprocessingImprovingEfficiency - 2
EPPENDORF_Nov2021_UpstreamBioprocessingImprovingEfficiency - Contents
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