Enhanced pyruvate production in Candida glabrata by overexpressing the CgAMD1 gene to improve acid tolerance.

ABSTRACT

OBJECTIVES: To enhance acid tolerance of Candida glabrata for pyruvate production by engineering AMP metabolism. RESULTS: The physiological function of AMP deaminase in AMP metabolism from C. glabrata was investigated by deleting or overexpresseing the corresponding gene, CgAMD1. At pH 4, CgAMD1 overexpression resulted in 59 and 51% increases in biomass and cell viability compared to those of wild type strain, respectively. In addition, the intracellular ATP level of strain Cgamd1Δ/CgAMD1 was down-regulated by 22%, which led to a 94% increase in pyruvate production. Further, various strengths of CgAMD1 expression cassettes were designed, thus resulting in a 59% increase in pyruvate production at pH 4. Strain Cgamd1Δ/CgAMD1 (H) was grown in a 30 l batch bioreactor at pH 4, and pyruvate reached 46.1 g/l. CONCLUSION: CgAMD1 overexpression plays an active role in improving acid tolerance and pyruvate fermentation performance of C. glabrata at pH 4.