(86c) Assessing the Metabolic Capabilities of the Yeast Issatchenkia Orientalis SD108 and Its Application to Biochemical Production

Many platform chemicals can be produced from renewable biomass by microorganisms, with organic acids making up a large number of these chemicals. Intolerance to the resulting low pH growth conditions, however, remains a challenge for the industrial production of organic acids by microorganisms. The yeast Issatchenkia orientalis SD108 is a promising host for industrial production because it is tolerant of low pH conditions. Here, we explore carbon substrate utilization capacity of I. orientalis SD108 by quantitatively measuring the growth rates, and examine differences with other strains. To systematically assess the metabolic capabilities of this non-model organism, we develop a genome-scale metabolic model for I. orientalis SD108 spanning 1,022 genes, 1,997 reactions, and 1,892 metabolites. In order to improve the quantitative predictions of the model, organism-specific macromolecular composition and ATP maintenance requirements were generated experimentally as part of this study, making use of chemostat data performed under carbon limited growth conditions. We examine its metabolic network topology, including essential genes, and draw comparisons with Saccharomyces cerevisiae. We also employ the model to survey the growth impact of targeted gene deletions and compare to the in vivo results we obtained by using a CRISPR/cas system. Next, we investigate and propose production pathways for succinic acid, through the use of the OptKnock framework to discern knockouts which link production of the targeted chemical to biomass production, and examine outcomes in vivo. Finally, we discuss implications for other industrially-relevant organic acids.