Modified Cyanobacteria for Producing Carotenoids
This disclosure describes modified photosynthetic microorganisms, including Cyanobacteria that produce carotenoids, including zeaxanthin, astaxanthin, and/or canthaxanthin. The modifications include one or more genetic modifications such as gene deletion, up regulation of an endogenous gene, and/or addition of an exogenous gene. In some embodiments the modified photosynthetic microorganisms may be subjected to stress conditions.
1 . A method of producing a carotenoid, the method comprising:
culturing a modified Cyanobacterium, the modified Cyanobacterium having decreased glycogen production; and
subjecting the modified Cyanobacterium to a stress condition during culturing, wherein the modified Cyanobacterium when subjected to the stress condition produces the carotenoid at a level greater than the corresponding wild-type Cyanobacterium subject to the same stress condition.
2 . (canceled)
3 . The method of claim 1 , wherein the carotenoid comprises zeaxanthin, astaxanthin, canthaxanthin, or a combination thereof.
4 - 6 . (canceled)
7 . The method of claim 1 , wherein the modified Cyanobacterium is modified by one of (i) deletion or inactivation of a glycogen pathway gene or (ii) by addition of a regulatable, exogenous promoter that controls transcription of a glycogen pathway gene.
8 . (canceled)
9 . The method of claim 7 , wherein the regulatable, exogenous promoter, when activated by a regulator, controls transcription of the glycogen pathway gene, the regulator comprises a nutrient, and the stress condition comprises deprivation of the nutrient.
10 . The method of claim 7 , wherein the glycogen pathway gene is glgC.
11 . The method of claim 1 , wherein the stress condition comprises at least one of high light, high salt, nutrient deprivation, nitrogen deprivation, sulfur deprivation, phosphorous deprivation, or iron deprivation.
12 - 14 . (canceled)
15 . The method of claim 1 , wherein the modified Cyanobacterium further comprises deletion of a crtG gene.
16 . The method of claim 15 , wherein the carotenoid comprises zeaxanthin.
17 . The method of claim 1 , wherein the modified Cyanobacterium further comprises an exogenous carotenoid ketolase gene.
18 - 19 . (canceled)
20 . A modified Cyanobacterium comprising:
a deleted or inactivated glycogen pathway gene,
wherein the modified Cyanobacterium, when subjected to a stress condition, produces a carotenoid at a level greater than the corresponding wild-type Cyanobacterium subject to the same stress condition.
21 - 23 . (canceled)
24 . The modified Cyanobacterium of claim 20 , further comprising an exogenous carotenoid ketolase gene.
25 - 26 . (canceled)
27 . The modified Cyanobacterium of claim 20 , wherein the glycogen pathway gene is glgC.
28 - 31 . (canceled)
32 . A method for generating modified Cyanobacterium, the method comprising:
deleting or inhibiting a glycogen pathway gene or addition of a regulatable, exogenous promoter that controls transcription of the glycogen pathway gene; and
adding an exogenous polynucleotide encoding an enzyme involved in the carotenoid biosynthesis pathway;
wherein the modified Cyanobacterium produces a carotenoid at a level greater than the corresponding wild-type Cyanobacterium.
33 - 34 . (canceled)
35 . The method of claim 32 , 33 , or 311 , wherein the glycogen pathway gene is glgC.
36 . The method of claim 32 , wherein the regulatable, exogenous promoter, when activated by a regulator, controls transcription of the one or more glycogen pathway genes and the regulator is a nutrient, and
wherein the absence of the nutrient causes the modified Cyanobacterium a stress condition.
37 . The method of claim 32 , wherein the enzyme involved in the carotenoid biosynthesis pathway is a carotenoid ketolase.
38 - 39 . (canceled)
40 . The method of claim 32 , further comprising addition of an exogenous crtZ gene and wherein the carotenoid is astaxanthin.
41 . The method of claim 32 , wherein the enzyme involved in the carotenoid biosynthesis pathway is a β-carotene hydroxylase.
42 . The method of claim 41 , wherein the carotenoid is zeaxanthin.
43 . The method of claim 32 , wherein the modified Cyanobacterium when subjected to a stress condition produces the carotenoid at the level greater than the corresponding wild-type Cyanobacterium subjected to the same stress condition.
44 - 45 . (canceled)