Effect of high 2-KLG concentration on expression of pivotal genes involved in 2-KLG synthesis in Gluconobacter oxydans WSH-003

Objective: To analyze the effect of high 2-keto-L-gulonic acid (2-KLG) on important dehydrogenase, cofactor and transport proteins involved in 2-KLG synthesis. Methods: First, the growth of Gluconobacter oxydans under high 2-KLG was observed. The real-time PCR was used to detect the expression of key sorbitol dehydrogenase gene sldAB, pyrroloquinoline quinone (PQQ) biosynthesis gene cluster pqqABCDE, and five genes encoding hypothetic PQQ transport proteins. Results: According to results of the growth of G. oxydans under different 2-KLG concentration, 40, 80 and 120 g/L 2-KLG were decided to stimulate strains. Real-time PCR showed that PQQ synthesis genes pqqABCDE were not affected by high 2-KLG, but sorbitol dehydrogenase genes sldAB and part of genes encoding PQQ transport proteins were down-regulated under high 2-KLG stress. Conclusion: The expression of sorbitol dehydrogenase genes was restrained by high 2-KLG, PQQ transport was probably inhibited, but PQQ synthesis was not affected.