Increased product formation induced by a directed secondary substrate limitation in a batch Hansenula polymorpha culture |
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Authors: | Kirsten Kottmeier Carsten Müller Robert Huber Jochen Büchs |
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Institution: | 1. Chair of Biochemical Engineering, RWTH Aachen University, Worringerweg 1, Sammelbau Biologie, 52056, Aachen, Germany 2. Institute of Genetics, Technische Universit?t Dresden, Zellscher Weg 20b, 01062, Dresden, Germany 3. m2p-labs GmbH, Forckenbeckstra?e 6, 52074, Aachen, Germany
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Abstract: | By the use of directed limitations of secondary substrates, the metabolic flux should be deflected from biomass production
to product formation. In order to study the impact of directed limitations caused by various secondary substrates on the growth
and product formation of the methylotrophic yeast Hansenula polymorpha, the cultivation systems respiration activity monitoring system (RAMOS) and BioLector were used in parallel. While the RAMOS
device allows the online monitoring of the oxygen transfer rate in shake flasks, the BioLector enables in microtiter plates
the monitoring of scattered light and the fluorescence intensity of the green fluorescent protein (GFP). Secondary substrate
limitations of phosphate, potassium, and magnesium were analyzed in batch fermentations. The sole carbon source was either
10 g/L glucose or 10 g/L glycerol. The expression of the GFP gene is controlled by the FMD promoter (formate dehydrogenase). In batch cultures with glucose as carbon source, a directed limitation of phosphate increased
the GFP production 1.87-fold, compared to phosphate unlimited conditions. Under potassium-limited conditions with glycerol
as sole carbon source, the GFP production was 1.41-fold higher compared to unlimited conditions. A limitation of the substrate
magnesium resulted in a 1.22-fold increase GFP formation in the case of glycerol as carbon source. |
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