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Probing Control of Glucose Feeding in Cultivation of <em>Saccharomyces cerevisiae</em>

Fredriksson, John (2001) In MSc Theses
Department of Automatic Control
Abstract
In order to maximize the biomass yield in fed-batch cultivations of Saccharomyces cerevisiae, a pulse feeding strategy originally developed by Mats Åkesson at the department of automatic con-trol (Åkesson, 1999), was implemented. The controller was intended to keep the specific glucose uptake rate, qs, below the critical specific glucose uptake rate qs crit , to avoid over-flow metabolism. Simulations, made to see if the method worked, and to find optimal working conditions, were done before the experiments. A robust PID controller was developed in order to regulate the dis-solved oxygen tension at 30%, by changing the stirrer speed.
Two different commercial strains of yeast (from Jästbolaget AB, Sweden) were used: the so-called blue... (More)
In order to maximize the biomass yield in fed-batch cultivations of Saccharomyces cerevisiae, a pulse feeding strategy originally developed by Mats Åkesson at the department of automatic con-trol (Åkesson, 1999), was implemented. The controller was intended to keep the specific glucose uptake rate, qs, below the critical specific glucose uptake rate qs crit , to avoid over-flow metabolism. Simulations, made to see if the method worked, and to find optimal working conditions, were done before the experiments. A robust PID controller was developed in order to regulate the dis-solved oxygen tension at 30%, by changing the stirrer speed.
Two different commercial strains of yeast (from Jästbolaget AB, Sweden) were used: the so-called blue yeast, for ordinary doughs, and the so-called red yeast, for sweet doughs. Glucose was the carbon source in the cultivations. The specific glucose uptake rate, qs, was controlled by the feed rate. If an up pulse in the feed rate resulted in a decrease of the DOT, below a certain point, the feed rate was increased in proportion to .DOT. If qs exceeded qs crit no decrease in DOT would be
seen, and therefore the feed rate was decreased. When the stirrer speed was close to its maximum value, a safety net in the regulator prevented further feed rate increase.
With the implemented control strategy growth was fully respirative. This was shown by high bio-mass yield values, low glucose and ethanol concentrations during the fed-batch cultivations, and also by a RQ, close to 1.08, throughout the fed-batch experiments. In some of the fed batch ex-periments, indications of synchronization of the culture could be seen.
The µ values were slightly lower than expected. Therefore one may suspect that qs never reached
qs crit , before the feed rate was decreased due to saturation in the oxygen transfer. In order to im-prove
the method, parameters like pulse length and initial cell mass concentration will have to be
adjusted. (Less)
Please use this url to cite or link to this publication:
author
Fredriksson, John
supervisor
organization
year
type
H3 - Professional qualifications (4 Years - )
subject
publication/series
MSc Theses
report number
TFRT-5660
ISSN
0280-5316
language
English
id
8848220
date added to LUP
2016-03-20 11:30:15
date last changed
2016-03-20 11:30:15
@misc{8848220,
  abstract     = {In order to maximize the biomass yield in fed-batch cultivations of Saccharomyces cerevisiae, a pulse feeding strategy originally developed by Mats Åkesson at the department of automatic con-trol (Åkesson, 1999), was implemented. The controller was intended to keep the specific glucose uptake rate, qs, below the critical specific glucose uptake rate qs crit , to avoid over-flow metabolism. Simulations, made to see if the method worked, and to find optimal working conditions, were done before the experiments. A robust PID controller was developed in order to regulate the dis-solved oxygen tension at 30%, by changing the stirrer speed.
Two different commercial strains of yeast (from Jästbolaget AB, Sweden) were used: the so-called blue yeast, for ordinary doughs, and the so-called red yeast, for sweet doughs. Glucose was the carbon source in the cultivations. The specific glucose uptake rate, qs, was controlled by the feed rate. If an up pulse in the feed rate resulted in a decrease of the DOT, below a certain point, the feed rate was increased in proportion to .DOT. If qs exceeded qs crit no decrease in DOT would be
seen, and therefore the feed rate was decreased. When the stirrer speed was close to its maximum value, a safety net in the regulator prevented further feed rate increase.
With the implemented control strategy growth was fully respirative. This was shown by high bio-mass yield values, low glucose and ethanol concentrations during the fed-batch cultivations, and also by a RQ, close to 1.08, throughout the fed-batch experiments. In some of the fed batch ex-periments, indications of synchronization of the culture could be seen.
The µ values were slightly lower than expected. Therefore one may suspect that qs never reached
qs crit , before the feed rate was decreased due to saturation in the oxygen transfer. In order to im-prove
the method, parameters like pulse length and initial cell mass concentration will have to be
adjusted.},
  author       = {Fredriksson, John},
  issn         = {0280-5316},
  language     = {eng},
  note         = {Student Paper},
  series       = {MSc Theses},
  title        = {Probing Control of Glucose Feeding in Cultivation of <em>Saccharomyces cerevisiae</em>},
  year         = {2001},
}