Enhancing ergosterol production in Pichia pastoris GS115 by overexpressing squalene synthase gene from Glycyrrhiza uralensis.

The present study was designed to determine the effects of copy number variations (CNVs) of squalene synthase 1( SQS 1) gene on the mevalonate (MVA) pathway. SQS 1 gene from G. uralensis ( Gu SQS1) was cloned and over-expressed in Pichia pastoris GS115. Six recombinant P. pastoris strains containing different copy number of Gu SQS1 were constructed. HPLC was used to assay the level of ergosterol in all transgenic P. pastoris strains containing Gu SQS1. HPLC analysis showed that the contents of ergosterol in all of the transgenic P. pastoris containing Gu SQS1 were higher than that in the negative control. And with the increase of copy number of Gu SQS1, the content of ergosterol showed an increasing-decreasing-increasing pattern. The contents of ergosterol in 10-copy- Gu SQS1 P. pastoris and 47-copy- Gu SQS1 P. pastoris were significantly higher than that in the rest recombinant P. pastoris strains. In conclusion, the CNVs of Gu SQS1 influence the content of secondary metabolites in the MVA pathway. The present study provides a basis for over-expressing Gu SQS1 and increasing the content of glycyrrhizin in G. uralensis cultivars. [ABSTRACT FROM AUTHOR]