(388b) Metabolic Engineering of Rhizopus Oryzae for Enhanced Production of Fumaric Acid From Sugars

Fumaric acid is a dicarboxylic acid used extensively in resins, food acidulants, and other applications including oil field fluids, esters etc. Some strains of Rhizopus oryzae, which is a filamentous fungus, can produce fumaric acid from sugars under aerobic conditions but the fumarate yield is relatively low due to the co-production of ethanol and other fermentation byproducts. In this work, metabolic engineering technique is applied to optimize the fermentation for enhanced fumaric acid production. Overexpression of native enzymes fumarase and pyruvate carboxylase showed no significant effect on the fumaric acid production, suggesting that the biosynthesis of fumaric acid is not limited by these two enzymes. On the other hand, overexpression of heterologous enzyme phosphoenolpyruvate carboxylase, which converts pyruvate with CO₂ fixation to oxaloacetate, led to increased fumaric acid production compared to the wild type control. The fermentation kinetics and activities of enzymes in the fermentation pathway of these Rhizopus mutants were studied and will be reported in this paper.