The oxygen transfer rate as key parameter for the characterization of Hansenula polymorpha screening cultures.
Screening cultures are usually non-monitored and non-controlled due to a lack of appropriate measuring techniques. A new device for online measurement of oxygen transfer rate (OTR) in shaking-flask cultures was used for monitoring the screening of Hansenula polymorpha. A shaking frequency of 300 rpm and a filling volume of 20 ml in 250-ml flasks ensured a sufficient oxygen transfer capacity of 0.032 mol (l h)(-1) and thus a respiration not limited by oxygen. Medium buffered with 0.01 mol phosphate l(-1) (pH 6.0) resulted in pH-inhibited respiration, whereas buffering with 0.12 mol phosphate l(-1) (pH 4.1) resulted in respiration that was not inhibited by pH. The ammonium demand was balanced by establishing fixed relations between oxygen, ammonium, and glycerol consumption with 0.245+/-0.015 mol ammonium per mol glycerol. Plate precultures with complex glucose medium reduced the specific growth rate coefficient to 0.18 h(-1) in subsequent cultures with minimal glycerol medium. The specific growth rate coefficient increased to 0.26 h(-1) when exponentially growing precultures with minimal glycerol medium were used for inoculation. Changes in biomass, glycerol, ammonium, and pH over time were simulated on the basis of oxygen consumption.
Stöckmann
Christoph
C
Biochemical Engineering, RWTH Aachen University, Worringerweg 1, Sammelbau Biologie, 52056, Aachen, Germany.
Maier
Ulrike
U
Anderlei
Tibor
T
Knocke
Christof
C
Gellissen
Gerd
G
Büchs
Jochen
J
D000970:Antineoplastic Agents / Q000378:metabolism; D001709:Biotechnology / Q000379:methods*; D003001:Cloning, Molecular; D003470:Culture Media; D005285:Fermentation; D005820:Genetic Testing / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000096:biosynthesis; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism*; D010843:Pichia / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D011994:Recombinant Proteins; D014498:Uracil / Q000378:metabolism
D000970:Antineoplastic Agents; D003470:Culture Media; D000077190:Interferon alpha-2; D016898:Interferon-alpha; D000644:Quaternary Ammonium Compounds; D011994:Recombinant Proteins; D014498:Uracil; D010100:Oxygen