Team:Johns Hopkins/Project/VitA


VitaYeast - Johns Hopkins University, iGEM 2011

Vitamin A

beta-Carotene (Vitamin A) and other carotenoids are present in many plants and share a common metabolic precursor with critical compounds including chlorophyll, tocopherol (Vitamin E), phylloquinone (Vitamin K1), squalene, and other sterols. Humans cannot naturally produce beta-Carotene, but require it for color vision.

betacarotene beta-Carotene


The Vitamin A production pathway template integrated into Saccharomyces cerevisiae was obtained from another strain of beta-Carotene-producing yeast, Xanthophyllomyces dendrorhous. S. cerevisiae has endogenous machinery to produce farnesyl diphosphate, but the rest of the pathway must be engineered. The missing caretenogenic genes included carotene desaturase, GGPP synthase, and phytoene synthase. The pathway for Vitamin A production is as follows:

Beta-carotene schematic (1).jpg

To make sure that the cells were indeed producing beta-Carotene, we verified beta-Carotene production using HPLC analysis. Once we were sure the strains containing the missing genes were expressing beta-Carotene, we tested its efficiency on a watered-down combination of dough, our intended final substrate, and agar. We characterized the yeast's beta-Carotene absorption over time on both YPD and dough media plates to observe the effects of substrate change on the beta-Carotene yield from the cells.

René Verwaal, Jing Wang, Jean-Paul Meijnen, Hans Visser, Gerhard Sandmann, Johan A. van den Berg, and Albert J. J. van Ooyen High-Level Production of Beta-Carotene in Saccharomyces cerevisiae by Successive Transformation with Carotenogenic Genes from Xanthophyllomyces dendrorhous Appl. Envir. Microbiol., July 1, 2007; 73: 4342 - 4350.

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