초록
β-Carotene biosynthesis in recombinant Saccharomyces cerevisiae was improved using inverse metabolic engineering. Determination of the transcriptional profiles of mevalonate pathway genes showed that transcription of HMG1, ERG8, ERG19 and ERG20 were induced in recombinant strain compared with the parent strain, whereas the expression of HMG2, ERG12 and IDI showed no significant differences. The contents of ergosterol and unsaturated fatty acids (UFAs) were decreased in recombinant yeast, and ERG9 and OLE1 involved in their syntheses were upregulated, suggesting that an increased demand exists for ergosterol and UFAs in recombinant yeast. Single overexpression of ERG19, ERG12 and ERG20 led to 11.0-32.2% increments in β-carotene content, but caused 22.9% and 13.6% decrements in overexpression of ERG8 and IDI1, respectively. In comparison, supplementation of 60mg/l oleic acid and palmitoleic acid led to 83.7% and 130.2% increments of β-carotene content, respectively, in parallel with recovery of UFA contents in cells. These results suggested that single overexpression of most genes in mevalonate pathway is not an effective approach for enhanced carotenoid production. However, intracellular UFA contents are important for carotenoid biosynthesis, and enriching UFA contents by exogenous supplementation or strengthening their biosynthesis might be a promising strategy to improve carotenoid production in recombinant S. cerevisiae.