Characterization of glycerol-3-phosphate dehydrogenase gene (CgGPD) from the glycerol producing Candida glycerinogenes

Abstract:

[Objective] Candida glycerinogenes, an excellent glycerol producer, has been used for commercial scale glycerol production. Recently, we cloned and sequenced the gene encoding NAD+-dependent glycerol 3-phosphate dehydrogenase (GPD) from C. glycerinogenes and this gene was named CgGPD, which plays an important role in glycerol production. However, compared with GPD1 and GPD2 from S. cerevisiae, the function of CgGPD was unclear to date. [Methods] In this study, a functional charaterization of CgGPD was undertaken, using S. cerevisiae and its isogenic gpd1/gpd2 mutant as expression host under high osmotic stress. [Results] Expression of CgGPD in wide type S. cerevisiae, using either TPI promoter from S. cerevisiae or upstream regulatory sequence of CgGPD accelerated glucose consumption rate and improved glycerol production signifcantly. In osmosensitive mutant, expresion of CgGPD including regulatory sequence increased cells osmotic tolernace and growth profile of transformants restored similar to wide type strain under the high osmotic stress condition. Furthermore, mutants harbouring CgGPD accumulated the intracellular glycerol content markedly and GPD specific enzyme activity increased abruptly when exposed to high osmolarity medium. [Conclusion] CgGPD from C. glycerinogenes compensate the GPD1 in S. cerevisiae functionally.