Converting Rhodosporidium Toruloides As a New Industrial Workhorse for the Production of Terpenes and Unusual Fatty Acids

Background: Fungal species in Rhodosporidium genera (also known as Rhodotorula, red yeasts) are outstanding native producers of lipid and carotenoid. In high density fermentation process, more than 100 g/L dried cell mass with more than 70% oil (triacylglyceride) can be produced within a week using glucose as the carbon source. Some strains are also able to produce more than 200 mg/L carotenoid. Interestingly, these yeasts have low oxygen demand during high density fermentation, a feature that is not seen in popular microbial hosts such as E. coli and Saccharomyces cerevisiae.

Results: We have established efficient genetic manupluation, gene expression and gene targeting tools for red yeast. By simply over-expressing a farnesyl diphosphate synthase and a sesquiterpene synthase, a sesquiterpene titer of more than more than 350 mg/L could be achieved in shake flask cultures. Transcriptomic analysis has identified many targets that are potentially limiting the production of terpenes in this host. At least 6 targets have been confirmed to enhance terpene yields, by 50-250% each gene. We have also systemically analyzed genes involved in fatty acid biosynthesis and degradation. A large collection of knockout mutants has been created, which allowed us to generate strains for the efficient production of various polyunsaturated fatty acids and fatty alcohols using glucose as the carbon source, such as alpha-linolenic acid (ALA), Tung (Vernicia fordii) oil and fatty alcohol.

Conclusions: Rhodotorula/Rhodosporidium are promising new hosts for the production of isoprenoids, fatty acids and their derivatives.