Key Process Conditions for Production of C4 Dicarboxylic Acids in Bioreactor Batch Cultures of an Engineered Saccharomyces cerevisiae Strain

Zelle, R.M.; De Hulster, E.; Kloezen, W.; Pronk, J.T.; Van Maris, A.J.A.

doi:doi:10.1128/AEM.02396-09

Key Process Conditions for Production of C4 Dicarboxylic Acids in Bioreactor Batch Cultures of an Engineered Saccharomyces cerevisiae Strain

Title

Key Process Conditions for Production of C4 Dicarboxylic Acids in Bioreactor Batch Cultures of an Engineered Saccharomyces cerevisiae Strain

Author

Zelle, R.M.
De Hulster, E.
Kloezen, W.
Pronk, J.T.
Van Maris, A.J.A.

Faculty

Applied Sciences

Department

Biotechnology

Date

2009-12-11

Abstract

A recent effort to improve malic acid production by Saccharomyces cerevisiae by means of metabolic engineering resulted in a strain that produced up to 59 g liter?1 of malate at a yield of 0.42 mol (mol glucose)?1 in calcium carbonate-buffered shake flask cultures. With shake flasks, process parameters that are important for scaling up this process cannot be controlled independently. In this study, growth and product formation by the engineered strain were studied in bioreactors in order to separately analyze the effects of pH, calcium, and carbon dioxide and oxygen availability. A near-neutral pH, which in shake flasks was achieved by adding CaCO3, was required for efficient C4 dicarboxylic acid production. Increased calcium concentrations, a side effect of CaCO3 dissolution, had a small positive effect on malate formation. Carbon dioxide enrichment of the sparging gas (up to 15% [vol/vol]) improved production of both malate and succinate. At higher concentrations, succinate titers further increased, reaching 0.29 mol (mol glucose)?1, whereas malate formation strongly decreased. Although fully aerobic conditions could be achieved, it was found that moderate oxygen limitation benefitted malate production. In conclusion, malic acid production with the engineered S. cerevisiae strain could be successfully transferred from shake flasks to 1-liter batch bioreactors by simultaneous optimization of four process parameters (pH and concentrations of CO2, calcium, and O2). Under optimized conditions, a malate yield of 0.48 ± 0.01 mol (mol glucose)?1 was obtained in bioreactors, a 19% increase over yields in shake flask experiments.

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DOI

https://doi.org/10.1128/AEM.02396-09

Publisher

American Society for Microbiology

ISSN

1098-5336

Source

APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Feb. 2010, p. 744–750

Part of collection

Institutional Repository