Production of isoprenoids
Provided herein are methods for a robust production of isoprenoids via one or more biosynthetic pathways. Also provided herein are nucleic acids, enzymes, expression vectors, and genetically modified host cells for carrying out the subject methods. Also provided herein are fermentation methods for high productivity of isoprenoids from genetically modified host cells.
1. A method for producing a heterologous C 5 -C 20 isoprenoid compound in a yeast host cell, the method comprising:
(a) obtaining a plurality of yeast host cells that are capable of making the heterologous C 5 -C 20 isoprenoid compound, each said yeast host cell comprising one or more heterologous nucleic acids capable of expressing each enzyme of the MEV pathway or each enzyme of the DXP pathway;
(b) culturing the yeast host cells in media comprising glucose and glucose-converted ethanol and an ethanol-only feed, wherein the culturing includes a period of time where the host cells are carbon-limited to yield a fermentation reaction mixture comprising medium, cells, and the heterologous C 5 -C 20 isoprenoid compound; and
(c) recovering the heterologous C 5 -C 20 isoprenoid compound from the medium,
wherein the yeast host cells produce from 10 to 40 grams of the heterologous C 5 -C 20 isoprenoid compound per liter of fermentation reaction mixture after 4 to 12 days of culturing, and
wherein the heterologous C5-C20 isoprenoid compound is farnesene.
2. The method of claim 1 , wherein the yeast host cells produce between 30 and 40 grams/liter of farnesene.
3. The method of claim 1 , wherein the yeast host cells produce greater than about 10 grams/liter of farnesene.
4. The method of claim 1 , wherein the yeast host cells produce greater than about 20 grams/liter of farnesene.
5. The method of claim 1 , wherein the yeast host cells are S. cerevisiae.
6. The method of claim 1 , wherein each said yeast host cell comprises one or more heterologous nucleic acids capable of expressing an acetyl-CoA acetyltransferase, an HMG-COA synthase, an HMG-CoA reductase, a mevalonate kinase, a phosphomevalonate kinase and a mevalonate pyrophosphate decarboxylase.
7. The method of claim 1 , wherein the medium comprises a batch medium and a feed medium.
8. The method of claim 7 , wherein the batch medium is supplied with 30 to 35 grams/liter phosphate.
9. The method of claim 1 , wherein the yeast host cells are maintained under carbon-limited conditions after the glucose and glucose-converted ethanol are depleted from the batch medium.
10. The method of claim 7 , comprising an overall ethanol consumption rate of 0 to 2.1 grams ethanol per gram of dry cell weight per day.
11. The method of claim 7 , wherein the batch medium is supplied with 30 to 35 grams/liter phosphate.
12. The method of claim 7 , wherein the feed medium is supplied at a maximum feed rate of 5 grams/hour/liter and a stationary feed rate of 1.25 grams/hour/liter to 2.5 grams/hour/liter.
13. The method of claim 7 , wherein the batch medium comprises glucose at 39.03 grams/liter and the feed medium is ethanol.
14. The method of claim 13 , wherein the feed medium is 95% ethanol.
15. The method of claim 8 , wherein the phosphate is supplied to the batch medium as potassium dihydrogen phosphate (KH 2 PO 4 ).