An Engineered Saccharomyces Cerevisiae for Producing (S)-3-Hydroxybutyrate

(S)-3-Hydroxybutyrate (S-3HB) can be used as an initial material for the synthesis of biodegradable polymers such as polyhydroxyalkanoate and stereo-specific fine chemicals such as antibiotics, vitamins, perfumes, and pheromones. To produce S-3HB in yeast, the biosynthetic pathway for the production of S-3HB from acetyl-CoA was introduced into Saccharomyces cerevisiae. The synthetic pathway of S-3HB involves the three enzymes from different microbial sources, acetyl-CoA C-acetyltransferase (ACCT), acetoacetyl-CoA reductase (ACR), and 3-hydroxybutyryl-CoA thioesterase (HBT) originating from S. cerevisiae, Clostridium acetobutylicum, and Escherichia coli, respectively. An engineered yeast strain overexpressing ERG10, hbd, and tesB genes not only exhibited enzyme activities of ACCT, ACR, and HBT, but also produced S-3HB from ethanol. To get a higher titer of S-3HB, a fed-batch fermentation based on pulse feeding of C2 compound (e.g., ethanol or acetate) as a carbon source was conducted, and a final S-3HB titer was 12.0g/L. To our knowledge, this is the first report on the production of 3HB by engineered yeast, utilizing ethanol as the carbon source, suggesting that the industrially preferred S. cerevisiae can be a promising host for producing S-3HB.