17-29: Reconstruction of the central carbon metabolism of Pichia stipitis

In view of rising concerns over energy sustainability and global warming, lignocellulosic ethanol has been identified as one of the most promising long-term renewable energy sources. However, many barriers exist for industrializing lignocellulosic ethanol processes, and the conversion of the pentoses (i.e., xylose and arabinose) to ethanol is one of the major barriers of industrializing lignocellulosic ethanol processes. Since Pichia stipitis is the most promising native strain for pentoses fermentation and it has shown good overall performance on hydrolysate, we aim to reconstruct the central carbon metabolism of P. stipitis to help understand its metabolic capabilities.

In this work, the topology of central carbon metabolism of P. stipitis was identified and the metabolic network was reconstructed by integrating genomic (P. stipitis v2.0, KEGG), biochemical (ChEBI, KEGG) and physiological information available for this microorganism and other related yeast. The stoichiometry of the metabolic reactions was used in combination with biosynthetic requirements for growth and pseudo-steady state mass balances over intracellular metabolites for the quantification of metabolic fluxes using metabolite balancing. This model was employed to perform an in silico characterization of the phenotypic behavior of P. stipitis grown on different carbon sources (glucose and xylose) and the model predictions are in general agreement with published experimental results. The effects on growth of single reaction deletions were assessed and essential biochemical reactions were identified for different carbon sources.