Using a System Identification based Framework to Elucidate How Scheffersomyces stipitis Shifts Redox in Response to Reduced Oxygen Supply

Abstract

Scheffersomyces stipitis has been recognized as an important yeast species in the field of biorenewables due to its native capacity for utilizing xylose. It has been well-recognized that redox (im)balance plays an important role for S. stipitis under oxygen limited conditions, in terms of ethanol production and xylitol (a by-product) production. However, there has not been any systems level understanding on how the shift in redox balance contribute to the overall metabolic shift in S. stipitis to cope with reduced oxygen uptake. In this work, with our recently developed genome-scale metabolic model (GEM) for S. stipitis, iDH814, we apply a system identification (SID) based framework to elucidate how the cellular metabolism of S. stipitis shifts in response to reduced oxygen supply. The systems level analysis indicates that S. stipitis uses a concerted approach to cope with the stress associated with reduced oxygen supply, and the shift of reducing power from NADPH to NADH seems to be the center theme that directs the overall shift in metabolic states.