Conference Dates

March 8-13, 2009

Abstract

Technology for the production of alternative fuels is receiving increased attention owing to concerns on global energy and environmental problems. Using higher carbon alcohols as gasoline substitutes has several advantages compared to ethanol, the first generation biofuel. Higher carbon alcohols also have other applications as flavor/aroma compounds and as building blocks for several other products. Two different pathways for the production of higher carbon alcohols have been recently reported. This work looks at evaluating the different pathways for higher carbon alcohol production and identification of metabolic bottlenecks for their production using Saccharomyces cerevisiae .

Quantitative characterization of the metabolic pathways of Saccharomyces cerevisiae is essential for understanding the metabolic behavior of the microorganism. Several mathematical modeling frameworks have been developed to describe and analyze the metabolic behavior of an organism. Stoichiometric modeling is one such approach which relies on mass balances over intracellular metabolites and the assumption of pseudo-steady-state conditions to determine intracellular metabolic fluxes. The development of stoichiometric models (metabolic models) and analysis of intracellular metabolic fluxes have several applications in metabolic engineering and strain improvement.

The production of higher carbon alcohols (such as 1-butanol, isobutanol, isopropanol) was analyzed by introducing the pathways into the genome scale metabolic model of Saccharomyces cerevisiae . The yield of higher carbon alcohols obtained from the fermentative and non-fermentative pathways was calculated and compared with maximum theoretical yield. The effect of different industrially relevant carbon sources on the production of higher carbon alcohols was also analyzed. Constraint based analysis was carried out on the genome scale metabolic model to obtain the intracellular metabolic flux distribution during the production of these alcohols. Detailed analysis of the metabolic flux distribution was carried out based on the shadow prices and reduced costs obtained from metabolic flux analysis. The metabolic bottlenecks for the production of higher carbon alcohols and the rate limiting steps in the metabolism were identified based on these analyses. Strategies for enhancing the yield of higher carbon alcohols will be proposed based on these analyses.

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