NADH-regulated metabolic model for growth of methylosinus trichosporium OB3b. Model presentation, parameter estimation, and model validation

• Published in: Biotechnology progress 2000-03, Vol.16 (2), p.176-188
• Main Authors: SIPKEMA, E. M, DE KONING, W, GANZEVELD, K. J, JANSSEN, D. B, BEENACKERS, A. A. C. M
• Format: Article
• Language: English
• Subjects: Adenosinetriphosphate; BIODEGRADATION; Biological and medical sciences; BIOLOGICAL PATHWAYS; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; Biotechnology - methods; carbon dioxide; CHLORINATED ALIPHATIC HYDROCARBONS; Computer Simulation; Culture Media; ENVIRONMENTAL SCIENCES; Enzyme kinetics; Formaldehyde; Formaldehyde - metabolism; Formates - metabolism; formic acid; Fundamental and applied biological sciences. Psychology; Fungi; GROWTH; Growth kinetics; Hydroxybutyrates - metabolism; Mathematical models; METABOLISM; METHANE; Methane - metabolism; Methanol; Methanol - metabolism; METHANOTROPHIC BACTERIA; Methylosinus trichosporium; Methylosinus trichosporium - growth & development; Methylosinus trichosporium - metabolism; Mission oriented research; Models, Biological; NAD - metabolism; NADH; NADH2; Nucleic acids; Physiology and metabolism; Polyesters - metabolism; polyhydroxybutyric acid; PQQ Cofactor; Quinolones - metabolism; Quinones - metabolism; REMEDIAL ACTION; Reproducibility of Results; Sensitivity and Specificity
• ISSN: 8756-7938; 1520-6033
• DOI: 10.1021/bp9901567

A biochemical model is presented that describes growth of Methylosinus trichosporium OB3b on methane. The model, which was developed to compare strategies to alleviate NADH limitation resulting from cometabolic contaminant conversion, includes (1) catabolism of methane via methanol, formaldehyde, and formate to carbon dioxide; (2) growth as formaldehyde assimilation; and (3) storage material (poly-beta-hydroxybutyric acid, PHB) metabolism. To integrate the three processes, the cofactor NADH is used as central intermediate and controlling factor-instead of the commonly applied energy carrier ATP. This way a stable and well-regulated growth model is obtained that gives a realistic description of a variety of steady-state and transient-state experimental data. An analysis of the cells' physiological properties is given to illustrate the applicability of the model. Steady-state model calculations showed that in strain OB3b flux control is located primarily at the first enzyme of the metabolic pathway. Since no adaptation in V(MAX) values is necessary to describe growth at different dilution rates, the organism seems to have a "rigid enzyme system", the activity of which is not regulated in response to continued growth at low rates. During transient periods of excess carbon and energy source availability, PHB is found to accumulate, serving as a sink for transiently available excess reducing power.