Print Email Facebook Twitter Maintenance-energy requirements and robustness of Saccharomyces cerevisiae at aerobic near-zero specific growth rates Title Maintenance-energy requirements and robustness of Saccharomyces cerevisiae at aerobic near-zero specific growth rates Author Vos, T. (TU Delft BT/Industriele Microbiologie) Hakkaart, X.D.V. (TU Delft BT/Industriele Microbiologie) de Hulster, A.F. (TU Delft BT/Industriele Microbiologie) van Maris, A.J.A. (TU Delft BT/Industriele Microbiologie) Pronk, J.T. (TU Delft BT/Industriele Microbiologie) Daran-Lapujade, P.A.S. (TU Delft BT/Industriele Microbiologie) Date 2016-06-17 Abstract Background: Saccharomyces cerevisiae is an established microbial platform for production of native and non-native compounds. When product pathways compete with growth for precursors and energy, uncoupling of growth and product formation could increase product yields and decrease formation of biomass as a by-product. Studying non-growing, metabolically active yeast cultures is a first step towards developing S. cerevisiae as a robust, non-growing cell factory. Microbial physiology at near-zero growth rates can be studied in retentostats, which are continuous-cultivation systems with full biomass retention. Hitherto, retentostat studies on S. cerevisiae have focused on anaerobic conditions, which bear limited relevance for aerobic industrial processes. The present study uses aerobic, glucose-limited retentostats to explore the physiology of non-dividing, respiring S. cerevisiae cultures, with a focus on industrially relevant features. Results: Retentostat feeding regimes for smooth transition from exponential growth in glucose-limited chemostat cultures to near-zero growth rates were obtained by model-aided experimental design. During 20 days of retentostats cultivation, the specific growth rate gradually decreased from 0.025 h-1 to below 0.001 h-1, while culture viability remained above 80 %. The maintenance requirement for ATP (mATP) was estimated at 0.63 ± 0.04 mmol ATP (g biomass)-1 h-1, which is ca. 35 % lower than previously estimated for anaerobic retentostats. Concomitant with decreasing growth rate in aerobic retentostats, transcriptional down-regulation of genes involved in biosynthesis and up-regulation of stress-responsive genes resembled transcriptional regulation patterns observed for anaerobic retentostats. The heat-shock tolerance in aerobic retentostats far exceeded previously reported levels in stationary-phase batch cultures. While in situ metabolic fluxes in retentostats were intentionally low due to extreme caloric restriction, off-line measurements revealed that cultures retained a high metabolic capacity. Conclusions: This study provides the most accurate estimation yet of the maintenance-energy coefficient in aerobic cultures of S. cerevisiae, which is a key parameter for modelling of industrial aerobic, glucose-limited fed-batch processes. The observed extreme heat-shock tolerance and high metabolic capacity at near-zero growth rates demonstrate the intrinsic potential of S. cerevisiae as a robust, non-dividing microbial cell factory for energy-intensive products. Subject AerobicEnergeticsHeat-shockMaintenanceRetentostatRobustnessYeastZero growth To reference this document use: http://resolver.tudelft.nl/uuid:a02bdca1-8fdd-4325-9115-1322ae953034 DOI https://doi.org/10.1186/s12934-016-0501-z ISSN 1475-2859 Source Microbial Cell Factories, 15 Part of collection Institutional Repository Document type journal article Rights © 2016 T. Vos, X.D.V. Hakkaart, A.F. de Hulster, A.J.A. van Maris, J.T. Pronk, P.A.S. Daran-Lapujade Files PDF art_10.1186_s12934_016_0501_z.pdf 3.21 MB Close viewer /islandora/object/uuid:a02bdca1-8fdd-4325-9115-1322ae953034/datastream/OBJ/view