Tailored oils
Recombinant DNA techniques are used to produce oleaginous recombinant cells that produce triglyceride oils having desired fatty acid profiles and regiospecific or stereospecific profiles. Genes manipulated include those encoding stearoyl-ACP desturase, delta 12 fatty acid desaturase, acyl-ACP thioesterase, ketoacyl-ACP synthase, and lysophosphatidic acid acyltransferase. The oil produced can have enhanced oxidative or thermal stability, or can be useful as a frying oil, shortening, roll-in shortening, tempering fat, cocoa butter replacement, as a lubricant, or as a feedstock for various chemical processes. The fatty acid profile can be enriched in midchain profiles or the oil can be enriched in triglycerides of the saturated-unsaturated-saturated type.
1. A method comprising:
(a) providing a recombinant oleaginous microalgal cell of the class Trebouxiophyte, the cell comprising an exogenous delta-12 fatty acid desaturase gene under control of an amt03 promoter and an allelic disruption of an endogenous delta-12 fatty acid desaturase gene;
(b) cultivating the cell under a first environmental condition wherein the exogenous delta-12 fatty acid desaturase gene is expressed, linoleic acid is produced and the cell divides, increasing the number of cells;
(c) cultivating the cells under a second environmental condition of reduced pH relative to the first environmental condition wherein expression of the exogenous delta-12 fatty acid desaturase gene and consequently production of linoleic acid is reduced and oil accumulates in the cells; and
(d) extracting the oil from the cells, wherein the oil is characterized by a polyunsaturated fatty acid profile with 5% linoleic acid or less.
2. The method of claim 1 , wherein the cell comprises 23S rRNA having at least 65% nucleotide sequence identity to SEQ ID NO:76.
3. The method of claim 1 , wherein the cell is an obligately heterotrophic microalga.
4. The method of claim 3 , wherein the cell is of the genus Prototheca.
5. The method of claim 1 , wherein the linoleic acid is reduced in the oil by at least 50%.
6. The method of claim 1 , wherein the cell is cultivated heterotrophically.
7. The method of claim 1 , wherein the cell produces at least 40% oil by dry cell weight.
8. The method of claim 1 , wherein, when extracted from the cell, the oil is stable at 110° C. so that the inflection point in conductance is not yet reached by 20 hours under conditions of the AOCS Cd 12b-92 Rancimat test.
9. The method of claim 1 , wherein, when extracted from the cell, the oil is stable at 110° C. so that the inflection point in conductance is not yet reached by 5 days under conditions of the AOCS Cd 12b-92 Rancimat test, when 1050 ppm of tocopherol and 500 pm of ascorbyl palmitate are added to the oil.
10. The method of claim 1 , wherein the cell comprises an exogenous gene encoding a KAS II enzyme.
11. The method of claim 10 , wherein the cell further comprises a knockout or knockdown of a FatA gene.
12. The method of claim 1 , wherein the oil is characterized by a fatty acid profile with greater than 60% oleic acid and less than 3% polyunsaturates.
13. The method of claim 1 , wherein the oil is characterized by a fatty acid profile with greater than 70% oleic acid and less than 2% polyunsaturates.
14. The method of claim 1 , wherein the oil is characterized by a fatty acid profile with greater than 80% oleic acid and less than 1% polyunsaturates.
15. The method of claim 1 , wherein the oil is characterized by a fatty acid profile with less 3% polyunsaturates or less.
16. The method of claim 1 , wherein the oil is characterized by a fatty acid profile with less than 2% polyunsaturates or less.
17. The method of claim 1 , wherein the oil is characterized by a fatty acid profile with less than 1% polyunsaturates or less.
18. The method of claim 1 , further comprising frying a food in the oil.
19. The method of claim 1 , wherein the cell division rate is decreased by more than 40% under the second environmental condition.