Enhancing production of ergosterol in Pichia pastoris GS115 by over-expression of 3-hydroxy-3-methylglutaryl CoA reductase from Glycyrrhiza uralensis

The rate-limiting enzyme in the mevalonic acid (MVA) pathway which can lead to triterpenoid saponin glycyrrhizic acid (GA) is 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR). In order to reveal the effect of copy number variation in the HMGR gene on the MVA pathway, the HMGR gene from Glycyrrhiza uralensis Fisch. (GuHMGR) was cloned and over-expressed in Pichia pastoris GS115. Six recombinant P. pastoris strains containing different copy numbers of the GuHMGR gene were obtained and the content of ergosterol was analyzed by HPLC. The results showed that all the recombinant P. pastoris strains contained more ergosterol than the negative control and the strains with 8 and 44 copies contained significantly more ergosterol than the other strains. However, as the copy number increased, the content of ergosterol showed an increasing–decreasing–increasing pattern. This study provides a rationale for increasing the content of GA through over-expressing the GuHMGR gene in cultivars of G. uralensis.

Graphical abstractSix recombinant Pichia pastoris strains containing different copy numbers of the GuHMGR gene were obtained in this paper. HPLC analysis showed that the content of ergosterol in all recombinant P. pastoris strains containing the GuHMGR gene was higher than in negative control. And with the increase of copy number of the GuHMGR gene, the content of ergosterol was presented in an increasing–decreasing–increasing pattern.Figure optionsDownload full-size imageDownload as PowerPoint slide