Improvement of coenzyme Q₁₀ production by increasing the NADH/NAD⁺ ratio in agrobacterium tumefaciens

Previously screened CoQ₁₀-overproducing Agrobacterium tumefaciens A603-35 showed a relatively high NADH/NAD⁺ ratio (1.1), as compared to parental strain C58 (0.2) when we increased the expression levels of NADH-generating enzymes. Also, the intracellular NADH/NAD⁺ ratio showed a positive correlation with the CoQ₁₀ content in A603-35. Overexpression of glyceraldehyde 3-phosphate dehydrogenase in A603-35 shifted the NADH/NAD⁺ ratio at 48 h from 0.8 to 1.2, and thus the CoQ ₁₀ content in flask culture increased from 2.16 to 3.63 mg/g DCW. Due to the addition of hydroxybutyrate to the culture media, the intracellular NADH/NAD⁺ ratio in A603-35-gapA shifted from 1.2 to 1.4, which led to an increase CoQ₁₀ content (5.27 mg/g DCW).