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Fina A, Millard P, Albiol J, Ferrer P, Heux S. High throughput 13C-metabolic flux analysis of 3-hydroxypropionic acid producing Pichia pastoris reveals limited availability of acetyl-CoA and ATP due to tight control of the glycolytic flux. Microb Cell Fact 2023; 22:117. [PMID: 37380999 DOI: 10.1186/s12934-023-02123-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 05/27/2023] [Indexed: 06/30/2023] Open
Abstract
BACKGROUND Production of 3-hydroxypropionic acid (3-HP) through the malonyl-CoA pathway has yielded promising results in Pichia pastoris (Komagataella phaffii), demonstrating the potential of this cell factory to produce this platform chemical and other acetyl-CoA-derived products using glycerol as a carbon source. However, further metabolic engineering of the original P. pastoris 3-HP-producing strains resulted in unexpected outcomes, e.g., significantly lower product yield and/or growth rate. To gain an understanding on the metabolic constraints underlying these observations, the fluxome (metabolic flux phenotype) of ten 3-HP-producing P. pastoris strains has been characterized using a high throughput 13C-metabolic flux analysis platform. Such platform enabled the operation of an optimised workflow to obtain comprehensive maps of the carbon flux distribution in the central carbon metabolism in a parallel-automated manner, thereby accelerating the time-consuming strain characterization step in the design-build-test-learn cycle for metabolic engineering of P. pastoris. RESULTS We generated detailed maps of the carbon fluxes in the central carbon metabolism of the 3-HP producing strain series, revealing the metabolic consequences of different metabolic engineering strategies aimed at improving NADPH regeneration, enhancing conversion of pyruvate into cytosolic acetyl-CoA, or eliminating by-product (arabitol) formation. Results indicate that the expression of the POS5 NADH kinase leads to a reduction in the fluxes of the pentose phosphate pathway reactions, whereas an increase in the pentose phosphate pathway fluxes was observed when the cytosolic acetyl-CoA synthesis pathway was overexpressed. Results also show that the tight control of the glycolytic flux hampers cell growth due to limited acetyl-CoA biosynthesis. When the cytosolic acetyl-CoA synthesis pathway was overexpressed, the cell growth increased, but the product yield decreased due to higher growth-associated ATP costs. Finally, the six most relevant strains were also cultured at pH 3.5 to assess the effect of a lower pH on their fluxome. Notably, similar metabolic fluxes were observed at pH 3.5 compared to the reference condition at pH 5. CONCLUSIONS This study shows that existing fluoxomics workflows for high-throughput analyses of metabolic phenotypes can be adapted to investigate P. pastoris, providing valuable information on the impact of genetic manipulations on the metabolic phenotype of this yeast. Specifically, our results highlight the metabolic robustness of P. pastoris's central carbon metabolism when genetic modifications are made to increase the availability of NADPH and cytosolic acetyl-CoA. Such knowledge can guide further metabolic engineering of these strains. Moreover, insights into the metabolic adaptation of P. pastoris to an acidic pH have also been obtained, showing the capability of the fluoxomics workflow to assess the metabolic impact of environmental changes.
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Affiliation(s)
- Albert Fina
- Department of Chemical, Biological and Environmental Engineering, Universitat Autònoma de Barcelona, Bellaterra, Catalonia, 08193, Spain
| | - Pierre Millard
- TBI, Université de Toulouse, CNRS, INRAE, INSA, Toulouse, 31077, France
| | - Joan Albiol
- Department of Chemical, Biological and Environmental Engineering, Universitat Autònoma de Barcelona, Bellaterra, Catalonia, 08193, Spain
| | - Pau Ferrer
- Department of Chemical, Biological and Environmental Engineering, Universitat Autònoma de Barcelona, Bellaterra, Catalonia, 08193, Spain.
| | - Stephanie Heux
- TBI, Université de Toulouse, CNRS, INRAE, INSA, Toulouse, 31077, France
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2
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De Brabander P, Uitterhaegen E, Delmulle T, De Winter K, Soetaert W. Challenges and progress towards industrial recombinant protein production in yeasts: A review. Biotechnol Adv 2023; 64:108121. [PMID: 36775001 DOI: 10.1016/j.biotechadv.2023.108121] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 02/07/2023] [Accepted: 02/07/2023] [Indexed: 02/12/2023]
Abstract
Recombinant proteins (RP) are widely used as biopharmaceuticals, industrial enzymes, or sustainable food source. Yeasts, with their ability to produce complex proteins through a broad variety of cheap carbon sources, have emerged as promising eukaryotic production hosts. As such, the prevalence of yeasts as favourable production organisms in commercial RP production is expected to increase. Yet, with the selection of a robust production host on the one hand, successful scale-up is dependent on a thorough understanding of the challenging environment and limitations of large-scale bioreactors on the other hand. In the present work, several prominent yeast species, including Saccharomyces cerevisiae, Pichia pastoris, Yarrowia lipolytica, Kluyveromyces lactis and Kluyveromyces marxianus are reviewed for their current state and performance in commercial RP production. Thereafter, the impact of principal process control parameters, including dissolved oxygen, pH, substrate concentration, and temperature, on large-scale RP production are discussed. Finally, technical challenges of process scale-up are identified. To that end, process intensification strategies to enhance industrial feasibility are summarized, specifically highlighting fermentation strategies to ensure sufficient cooling capacity, overcome oxygen limitation, and increase protein quality and productivity. As such, this review aims to contribute to the pursuit of sustainable yeast-based RP production.
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Affiliation(s)
- Pieter De Brabander
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Department of Biotechnology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium; Bio Base Europe Pilot Plant (BBEPP), Rodenhuizekaai 1, 9042 Ghent (Desteldonk), Belgium
| | - Evelien Uitterhaegen
- Bio Base Europe Pilot Plant (BBEPP), Rodenhuizekaai 1, 9042 Ghent (Desteldonk), Belgium
| | - Tom Delmulle
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Department of Biotechnology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Karel De Winter
- Bio Base Europe Pilot Plant (BBEPP), Rodenhuizekaai 1, 9042 Ghent (Desteldonk), Belgium.
| | - Wim Soetaert
- Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Department of Biotechnology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium; Bio Base Europe Pilot Plant (BBEPP), Rodenhuizekaai 1, 9042 Ghent (Desteldonk), Belgium
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3
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Tan LR, Liu JJ, Deewan A, Lee JW, Xia PF, Rao CV, Jin YS, Wang SG. Genome-wide transcriptional regulation in Saccharomyces cerevisiae in response to carbon dioxide. FEMS Yeast Res 2022; 22:6595876. [PMID: 35640892 DOI: 10.1093/femsyr/foac032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 04/30/2022] [Accepted: 05/26/2022] [Indexed: 11/12/2022] Open
Abstract
Sugar metabolism by Saccharomyces cerevisiae produces ample amounts of CO2 under both aerobic and anaerobic conditions. High solubility of CO2 in fermentation media, contributing to enjoyable sensory properties of sparkling wine and beers by S. cerevisiae, might affect yeast metabolism. To elucidate the overlooked effects of CO2 on yeast metabolism, we examined glucose fermentation by S. cerevisiae under CO2 as compared to N2 and O2 limited conditions. While both CO2 and N2 conditions are considered anaerobic, less glycerol and acetate but more ethanol were produced under CO2 condition. Transcriptomic analysis revealed that significantly decreased mRNA levels of GPP1 coding for glycerol-3-phosphate phosphatase in glycerol synthesis explained the reduced glycerol production under CO2 condition. Besides, transcriptional regulations in signal transduction, carbohydrate synthesis, heme synthesis, membrane and cell wall metabolism, and respiration were detected in response to CO2. Interestingly, signal transduction was uniquely regulated under CO2 condition, where up-regulated genes (STE3, MSB2, WSC3, STE12 and TEC1) in the signal sensors and transcriptional factors suggested that MAPK signaling pathway plays a critical role in CO2 sensing and CO2-induced metabolisms in yeast. Our study identifies CO2 as an external stimulus for modulating metabolic activities in yeast and a transcriptional effector for diverse applications.
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Affiliation(s)
- Lin-Rui Tan
- School of Environmental Science and Engineering, Shandong University, Qingdao 266237, P. R. China.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Jing-Jing Liu
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Anshu Deewan
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.,Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Jae Won Lee
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Peng-Fei Xia
- School of Environmental Science and Engineering, Shandong University, Qingdao 266237, P. R. China
| | - Christopher V Rao
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.,Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Yong-Su Jin
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.,Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Shu-Guang Wang
- School of Environmental Science and Engineering, Shandong University, Qingdao 266237, P. R. China.,Sino-French Research Institute for Ecology and Environment, Shandong University, Qingdao 266237, P. R. China
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Robustness: linking strain design to viable bioprocesses. Trends Biotechnol 2022; 40:918-931. [PMID: 35120750 DOI: 10.1016/j.tibtech.2022.01.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 01/05/2022] [Accepted: 01/05/2022] [Indexed: 12/18/2022]
Abstract
Microbial cell factories are becoming increasingly popular for the sustainable production of various chemicals. Metabolic engineering has led to the design of advanced cell factories; however, their long-term yield, titer, and productivity falter when scaled up and subjected to industrial conditions. This limitation arises from a lack of robustness - the ability to maintain a constant phenotype despite the perturbations of such processes. This review describes predictable and stochastic industrial perturbations as well as state-of-the-art technologies to counter process variability. Moreover, we distinguish robustness from tolerance and discuss the potential of single-cell studies for improving system robustness. Finally, we highlight ways of achieving consistent and comparable quantification of robustness that can guide the selection of strains for industrial bioprocesses.
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Eigenfeld M, Kerpes R, Becker T. Recombinant protein linker production as a basis for non-invasive determination of single-cell yeast age in heterogeneous yeast populations. RSC Adv 2021; 11:31923-31932. [PMID: 35495491 PMCID: PMC9041608 DOI: 10.1039/d1ra05276d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 09/16/2021] [Indexed: 11/30/2022] Open
Abstract
The physiological and metabolic diversity of a yeast culture is the sum of individual cell phenotypes. As well as environmental conditions, genetics, and numbers of cell divisions, a major factor influencing cell characteristics is cell age. A postcytokinesis bud scar on the mother cell, a benchmark in the replicative life span, is a quantifiable indicator of cell age, characterized by significant amounts of chitin. We developed a binding process for visualizing the bud scars of Saccharomyces pastorianus var. carlsbergensis using a protein linker containing a polyhistidine tag, a superfolder green fluorescent protein (sfGFP), and a chitin-binding domain (His6-SUMO-sfGFP-ChBD). The binding did not affect yeast viability; thus, our method provides the basis for non-invasive cell age determination using flow cytometry. The His6-SUMO-sfGFP-ChBD protein was synthesized in Escherichia coli, purified using two-stage chromatography, and checked for monodispersity and purity. Linker-cell binding and the characteristics of the bound complex were determined using flow cytometry and confocal laser scanning microscopy (CLSM). Flow cytometry showed that protein binding increased to 60 455 ± 2706 fluorescence units per cell. The specific coupling of the linker to yeast cells was additionally verified by CLSM and adsorption isotherms using yeast cells, E. coli cells, and chitin resin. We found a relationship between the median bud scar number, the median of the fluorescence units, and the chitin content of yeast cells. A fast measurement of yeast population dynamics by flow cytometry is possible, using this protein binding technique. Rapid qualitative determination of yeast cell age distribution can therefore be performed.
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Affiliation(s)
- Marco Eigenfeld
- Technical University of Munich, Chair of Brewing and Beverage Technology, Research Group Beverage and Cereal Biotechnology Weihenstephaner Steig 20 85354 Freising Germany
| | - Roland Kerpes
- Technical University of Munich, Chair of Brewing and Beverage Technology, Research Group Beverage and Cereal Biotechnology Weihenstephaner Steig 20 85354 Freising Germany
| | - Thomas Becker
- Technical University of Munich, Chair of Brewing and Beverage Technology, Research Group Beverage and Cereal Biotechnology Weihenstephaner Steig 20 85354 Freising Germany
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6
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Liu Y, Esen O, Pronk JT, van Gulik WM. Uncoupling growth and succinic acid production in an industrial Saccharomyces cerevisiae strain. Biotechnol Bioeng 2021; 118:1576-1586. [PMID: 33410171 PMCID: PMC8048565 DOI: 10.1002/bit.27672] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 12/13/2020] [Accepted: 12/29/2020] [Indexed: 12/12/2022]
Abstract
This study explores the relation between biomass‐specific succinic acid (SA) production rate and specific growth rate of an engineered industrial strain of Saccharomyces cerevisiae, with the aim to investigate the extent to which growth and product formation can be uncoupled. Ammonium‐limited aerobic chemostat and retentostat cultures were grown at different specific growth rates under industrially relevant conditions, that is, at a culture pH of 3 and with sparging of a 1:1 CO2–air mixture. Biomass‐specific SA production rates decreased asymptotically with decreasing growth rate. At near‐zero growth rates, the engineered strain maintained a stable biomass‐specific SA production rate for over 500 h, with a SA yield on glucose of 0.61 mol mol−1. These results demonstrate that uncoupling of growth and SA production could indeed be achieved. A linear relation between the biomass‐specific SA production rate and glucose consumption rate indicated the coupling of SA production rate and the flux through primary metabolism. The low culture pH resulted in an increased death rate, which was lowest at near‐zero growth rates. Nevertheless, a significant amount of non‐viable biomass accumulated in the retentostat cultures, thus underlining the importance of improving low‐pH tolerance in further strain development for industrial SA production with S. cerevisiae.
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Affiliation(s)
- Yaya Liu
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands
| | - Osman Esen
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands
| | - Jack T Pronk
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands
| | - Walter M van Gulik
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands
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7
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Impact of Altered Trehalose Metabolism on Physiological Response of Penicillium chrysogenum Chemostat Cultures during Industrially Relevant Rapid Feast/Famine Conditions. Processes (Basel) 2021. [DOI: 10.3390/pr9010118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Due to insufficient mass transfer and mixing issues, cells in the industrial-scale bioreactor are often forced to experience glucose feast/famine cycles, mostly resulting in reduced commercial metrics (titer, yield and productivity). Trehalose cycling has been confirmed as a double-edged sword in the Penicillium chrysogenum strain, which facilitates the maintenance of a metabolically balanced state, but it consumes extra amounts of the ATP responsible for the repeated breakdown and formation of trehalose molecules in response to extracellular glucose perturbations. This loss of ATP would be in competition with the high ATP-demanding penicillin biosynthesis. In this work, the role of trehalose metabolism was further explored under industrially relevant conditions by cultivating a high-yielding Penicillium chrysogenum strain, and the derived trehalose-null strains in the glucose-limited chemostat system where the glucose feast/famine condition was imposed. This dynamic feast/famine regime with a block-wise feed/no feed regime (36 s on, 324 s off) allows one to generate repetitive cycles of moderate changes in glucose availability. The results obtained using quantitative metabolomics and stoichiometric analysis revealed that the intact trehalose metabolism is vitally important for maintaining penicillin production capacity in the Penicillium chrysogenum strain under both steady state and dynamic conditions. Additionally, cells lacking such a key metabolic regulator would become more sensitive to industrially relevant conditions, and are more able to sustain metabolic rearrangements, which manifests in the shrinkage of the central metabolite pool size and the formation of ATP-consuming futile cycles.
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8
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Predicting By-Product Gradients of Baker’s Yeast Production at Industrial Scale: A Practical Simulation Approach. Processes (Basel) 2020. [DOI: 10.3390/pr8121554] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Scaling up bioprocesses is one of the most crucial steps in the commercialization of bioproducts. While it is known that concentration and shear rate gradients occur at larger scales, it is often too risky, if feasible at all, to conduct validation experiments at such scales. Using computational fluid dynamics equipped with mechanistic biochemical engineering knowledge of the process, it is possible to simulate such gradients. In this work, concentration profiles for the by-products of baker’s yeast production are investigated. By applying a mechanistic black-box model, concentration heterogeneities for oxygen, glucose, ethanol, and carbon dioxide are evaluated. The results suggest that, although at low concentrations, ethanol is consumed in more than 90% of the tank volume, which prevents cell starvation, even when glucose is virtually depleted. Moreover, long exposure to high dissolved carbon dioxide levels is predicted. Two biomass concentrations, i.e., 10 and 25 g/L, are considered where, in the former, ethanol production is solely because of overflow metabolism while, in the latter, 10% of the ethanol formation is due to dissolved oxygen limitation. This method facilitates the prediction of the living conditions of the microorganism and its utilization to address the limitations via change of strain or bioreactor design or operation conditions. The outcome can also be of value to design a representative scale-down reactor to facilitate strain studies.
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9
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Understanding gradients in industrial bioreactors. Biotechnol Adv 2020; 46:107660. [PMID: 33221379 DOI: 10.1016/j.biotechadv.2020.107660] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 10/22/2020] [Accepted: 11/14/2020] [Indexed: 01/07/2023]
Abstract
Gradients in industrial bioreactors have attracted substantial research attention since exposure to fluctuating environmental conditions has been shown to lead to changes in the metabolome, transcriptome as well as population heterogeneity in industrially relevant microorganisms. Such changes have also been found to impact key process parameters like the yield on substrate and the productivity. Hence, understanding gradients is important from both the academic and industrial perspectives. In this review the causes of gradients are outlined, along with their impact on microbial physiology. Quantifying the impact of gradients requires a detailed understanding of both fluid flow inside industrial equipment and microbial physiology. This review critically examines approaches used to investigate gradients including large-scale experimental work, computational methods and scale-down approaches. Avenues for future work have been highlighted, particularly the need for further coordinated development of both in silico and experimental tools which can be used to further the current understanding of gradients in industrial equipment.
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10
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Uncovering mechanisms of greengage wine fermentation against acidic stress via genomic, transcriptomic, and metabolic analyses of Saccharomyces cerevisiae. Appl Microbiol Biotechnol 2020; 104:7619-7629. [DOI: 10.1007/s00253-020-10772-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 06/15/2020] [Accepted: 07/02/2020] [Indexed: 02/08/2023]
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11
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Xiberras J, Klein M, de Hulster E, Mans R, Nevoigt E. Engineering Saccharomyces cerevisiae for Succinic Acid Production From Glycerol and Carbon Dioxide. Front Bioeng Biotechnol 2020; 8:566. [PMID: 32671027 PMCID: PMC7332542 DOI: 10.3389/fbioe.2020.00566] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/11/2020] [Indexed: 12/11/2022] Open
Abstract
Previously, our lab replaced the endogenous FAD-dependent pathway for glycerol catabolism in S. cerevisiae by the synthetic NAD-dependent dihydroxyacetone (DHA) pathway. The respective modifications allow the full exploitation of glycerol’s higher reducing power (compared to sugars) for the production of the platform chemical succinic acid (SA) via a reductive, carbon dioxide fixing and redox-neutral pathway in a production host robust for organic acid production. Expression cassettes for three enzymes converting oxaloacetate to SA in the cytosol (“SA module”) were integrated into the genome of UBR2CBS-DHA, an optimized CEN.PK derivative. Together with the additional expression of the heterologous dicarboxylic acid transporter DCT-02 from Aspergillus niger, a maximum SA titer of 10.7 g/L and a yield of 0.22 ± 0.01 g/g glycerol was achieved in shake flask (batch) cultures. Characterization of the constructed strain under controlled conditions in a bioreactor supplying additional carbon dioxide revealed that the carbon balance was closed to 96%. Interestingly, the results of the current study indicate that the artificial “SA module” and endogenous pathways contribute to the SA production in a highly synergistic manner.
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Affiliation(s)
- Joeline Xiberras
- Department of Life Sciences and Chemistry, Jacobs University Bremen gGmbH, Bremen, Germany
| | - Mathias Klein
- Department of Life Sciences and Chemistry, Jacobs University Bremen gGmbH, Bremen, Germany
| | - Erik de Hulster
- Department of Biotechnology, Delft University of Technology, Delft, Netherlands
| | - Robert Mans
- Department of Biotechnology, Delft University of Technology, Delft, Netherlands
| | - Elke Nevoigt
- Department of Life Sciences and Chemistry, Jacobs University Bremen gGmbH, Bremen, Germany
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12
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Hakkaart X, Liu Y, Hulst M, El Masoudi A, Peuscher E, Pronk J, van Gulik W, Daran-Lapujade P. Physiological responses of Saccharomyces cerevisiae to industrially relevant conditions: Slow growth, low pH, and high CO 2 levels. Biotechnol Bioeng 2020; 117:721-735. [PMID: 31654410 PMCID: PMC7028085 DOI: 10.1002/bit.27210] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 10/12/2019] [Accepted: 10/22/2019] [Indexed: 12/21/2022]
Abstract
Engineered strains of Saccharomyces cerevisiae are used for industrial production of succinic acid. Optimal process conditions for dicarboxylic‐acid yield and recovery include slow growth, low pH, and high CO2. To quantify and understand how these process parameters affect yeast physiology, this study investigates individual and combined impacts of low pH (3.0) and high CO2 (50%) on slow‐growing chemostat and retentostat cultures of the reference strain S. cerevisiae CEN.PK113‐7D. Combined exposure to low pH and high CO2 led to increased maintenance‐energy requirements and death rates in aerobic, glucose‐limited cultures. Further experiments showed that these effects were predominantly caused by low pH. Growth under ammonium‐limited, energy‐excess conditions did not aggravate or ameliorate these adverse impacts. Despite the absence of a synergistic effect of low pH and high CO2 on physiology, high CO2 strongly affected genome‐wide transcriptional responses to low pH. Interference of high CO2 with low‐pH signaling is consistent with low‐pH and high‐CO2 signals being relayed via common (MAPK) signaling pathways, notably the cell wall integrity, high‐osmolarity glycerol, and calcineurin pathways. This study highlights the need to further increase robustness of cell factories to low pH for carboxylic‐acid production, even in organisms that are already applied at industrial scale.
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Affiliation(s)
- Xavier Hakkaart
- Department of Biotechnology, Delft University of Technology, van der Maasweg, Delft, The Netherlands
| | - Yaya Liu
- Department of Biotechnology, Delft University of Technology, van der Maasweg, Delft, The Netherlands
| | - Mandy Hulst
- Department of Biotechnology, Delft University of Technology, van der Maasweg, Delft, The Netherlands
| | - Anissa El Masoudi
- Department of Biotechnology, Delft University of Technology, van der Maasweg, Delft, The Netherlands
| | - Eveline Peuscher
- Department of Biotechnology, Delft University of Technology, van der Maasweg, Delft, The Netherlands
| | - Jack Pronk
- Department of Biotechnology, Delft University of Technology, van der Maasweg, Delft, The Netherlands
| | - Walter van Gulik
- Department of Biotechnology, Delft University of Technology, van der Maasweg, Delft, The Netherlands
| | - Pascale Daran-Lapujade
- Department of Biotechnology, Delft University of Technology, van der Maasweg, Delft, The Netherlands
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