Evaluation Of The Yeast Promoters In Kluyveromyces Marxianus

The unique features of Kluyveromyces marxianus, including broad substrate spectrum, thermo-tolerance, high growth rate, and so on, make this yeast a promising biotechnological tool for future applications. However, the application of K. marxianus is still limited by a lack of engineering tools. One of the limitations is that the promoters of K. marxianus are not well characterized yet.In this study, six constitutive promoters (PTDH3,PPGK, and PADHI from S. cerevisiae and K. marxianus) were evaluated in K.marxianus through expression of the heterologous KILACZ, GUSA, and SH BLE genes. While the transcription of all the promoters decreased at higher temperatures.the order of their promoting strength at various temperatures was determined as PKmPGK>PKmTDH3> PScPGK>PScTDH3> PKmADH1> PScADH1 with glucose as the carbon source. At 45 ℃,PKmPGK and PKmTDH3 from K. marxianus maintained a comparatively stronger promoting ability. However, when glycerol was supplied as the carbon source, the strength of PKmTDH3 decreased significantly while the promoting ability of PKmADH1 and PScADH1 increased. The promoting ability of all promoters decreased with xylose as the carbon source, while PKmPGK maintained a relatively higher strength. The promoters from K. marxianus were stronger than those from S. cerevisiae with glucose as the carbon source. However, when glycerol was supplied as the carbon source,PKmTDH3 was found to be weaker than PScTDH3. These results provide useful information for the selection of appropriate promoters in the metabolic engineering of K. marxianus at various temperatures.