Ergosterol production from molasses by genetically modified Saccharomyces cerevisiae

• Published in: Applied microbiology and biotechnology Vol. 75; no. 1; pp. 55 - 60
• Main Authors: He, Xiuping, Guo, Xuena, Liu, Nan, Zhang, Borun
• Format: Journal Article
• Language: English
• Published: Berlin Berlin/Heidelberg : Springer-Verlag 01-05-2007; Springer; Springer Nature B.V
• Subjects: Acyltransferases - genetics; Acyltransferases - metabolism; Bioengineering; Biological and medical sciences; Biomass; Bioreactors; Biosynthesis; Biotechnology; Biotechnology - methods; Carbon; Carbon sources; Combined overexpression; Culture Media; Economic importance; ergosterol; Ergosterol - biosynthesis; Ethanol; Fed-batch fermentation; Fermentation; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Enzymologic; Genetic engineering; Genetically altered foods; Metabolites; Molasses; Oxidoreductases - genetics; Oxidoreductases - metabolism; Plasmids; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - growth & development; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Sterol acyltransferase; Sterol C-24 reductase; Sterols; Studies; Sugar; Syrups & sweeteners; Up-Regulation; Urea; Yeast; Yeasts; Fungi; Ergosterol; Yeast; Molasses; Production; Ascomycetes; Genetically modified organism; Saccharomyces cerevisiae; Thallophyta
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-006-0807-6

Ergosterol is an economically important metabolite produced by fungi. Recombinant Saccharomyces cerevisiae YEH56(pHXA42) with increased capacity of ergosterol formation was constructed by combined overexpression of sterol C-24(28) reductase and sterol acyltransferase in the yeast strain YEH56. The production of ergosterol by this recombinant strain using cane molasses (CM) as an inexpensive carbon source was investigated. An ergosterol content of 52.6 mg/g was obtained with 6.1 g/l of biomass from CM medium containing 60 g/l of total sugar in 30 h in shake flask. The ergosterol yield was enhanced through the increasing cell biomass by supplementation of urea to a concentration of 6 g/l in molasses medium. Fermentation was performed in 5-l bioreactor using the optimized molasses medium. In batch fermentation, the effect of agitation velocity on ergosterol production was examined. The highest ergosterol yield was obtained at 400 rpm that increased 60.4 mg/l in comparison with the shake flask culture. In fed-batch fermentation, yeast cells were cultivated, firstly, in the starting medium containing molasses with 20 g/l of total sugar, 1.68 g/l of phosphate acid, and 6 g/l of urea (pH 5.4) for 5 h, then molasses containing 350 g/l of total sugar was fed exponentially into the bioreactor to keep the ethanol level in the broth below 0.5%. After 40 h of cultivation, the ergosterol yield reached 1,707 mg/l, which was 3.1-fold of that in the batch fermentation.