(378a) Cofermentation of Mixed Sugars to Bioethanol with Single and Multiple Yeast Strains: Model Development

Bioethanol is an energy resource with a promising future for its superiority in high flammability, lesser pollution, and reduced greenhouse gas emissions. In this work, we initiate modeling to investigate the production efficiency of bioethanol with single and multiple yeast strains from mixed sugars. Our approach is based on hybrid cybernetic model (HCM) (Kim et al., 2008; Song and Ramkrishna, 2009; Song et al., 2009) which combines the cybernetic regulatory mechanisms with elementary mode (EM) analysis based on quasi-steady-state approximation on intracellular metabolites, viewing uptake flux to be distributed in a regulated way among different EMs. With this feature, HCM provides a suitable framework for simulating the fermentation of mixed sugars which can be consumed sequentially or simultaneously. As case studies, HCM is applied to cofermentation of glucose, xylose, mannose and galactose using three different individual yeast strains, respectively, i.e., Saccharomyces cerevisiae, Pichia stipitis and Kluyveromyces marxianus, showing satisfactory fits to experimental data. The model is now being extended to coculture of mixed strains which are often considered to create a synergistic effect in producing bioethanol. It is expected that the developed model will be a valuable tool for optimizing the fermentation process towards maximizing bioethanol productivity.

References:

Kim JI, Varner JD, Ramkrishna D. 2008. A hybrid model of anaerobic E. coli GJ T001: Combination of elementary flux modes and cybernetic variables. Biotechnol Prog 24(5):993?1006.

Song HS, Ramkrishna D. 2009a. Reduction of a set of elementary modes using yield analysis. Biotechnol Bioeng 102(2):554?568.

Song HS, Morgan JA, Ramkrishna D. 2009. Systematic Development of Hybrid Cybernetic Models: Application to Recombinant Yeast Co-consuming Glucose and Xylose, Biotechnology and Bioengineering 103(5): 984-102