Structuring fats and methods of producing structuring fats
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 desaturase, 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. An oleaginous microalgal cell of the genus Prototheca , the cell comprising an exogenous heterologous gene encoding an active lysophosphatidic acid acyltransferase (LPAAT) enzyme, the cell producing an oil comprising triglycerides, wherein the oil is, by virtue of the LPAAT activity:
(a) enriched in triglycerides with midchain fatty acids; or
(b) enriched in triglycerides of the saturated-unsaturated-saturated type.
2. The cell of claim 1 , wherein the triglycerides of the oil comprise 40, 50, 60, 70, or 80% or more of C8:0, C10:0, C12:0, C14:0, or C16:0 fatty acids.
3. The cell of claim 1 , wherein the cell further comprises:
(a) an exogenous gene encoding an active fatty acyl-ACP thioesterase;
(b) recombinant nucleic acids operable to encode an exogenous KAS I or KAS IV enzyme or to reduce the activity of an endogenous KAS I enzyme; and/or
(c) nucleic acids operable to reduce the expression of a delta 12 fatty acid desaturase.
4. The cell of claim 1 , wherein the oil is enriched in SOS, POS, and/or POP, or wherein the oil comprises triglycerides comprising at least 50% SOS and less than 10% SSS.
5. The cell of claim 4 , further comprising:
(a) a knockout or knockdown of a stearoyl-ACP desaturase gene, fatty acyl-ACP thioesterase gene, or both; and/or
(b) recombinant nucleic acids operable to increase ketoacyl-ACP synthase (KAS) activity.
6. The cell of claim 4 , wherein:
(a) the ratio of stearate to oleate in oil is 3:1±20%;
(b) POP, SOS, and POS in the oil comprise at least 30% in sum;
(c) the oil comprises at least 30% POS;
(d) the oil comprises POP at 16%±20%, POS at 38%±20%, and SOS at 23%±20%; and/or
(e) the fatty acid profile of the oil comprises 1 to 4% arachidic acid.
7. The cell of claim 4 , wherein:
(a) the cell further comprises nucleic acids operable to reduce the expression of a delta 12 fatty acid desaturase;
(b) the oil has greater than 65% SOS, less than 45% unsaturated fatty acid, less than 5% polyunsaturated fatty acids, less than 1% lauric acid, and less than 2% trans fatty acids; and/or
(c) the LPAAT has the amino acid sequence of SEQ ID NO: 78 or SEQ ID NO: 79 or a sequence having at least 95% identity to SEQ ID NO:78 or SEQ ID NO: 79.
8. The cell of claim 1 , wherein the cell is Prototheca moriformis.
9. A method for producing an oil comprising providing or cultivating a cell according to claim 1 , and extracting the oil, the cell being cultivated heterotrophically.
10. A method according to claim 9 , wherein the oil comprises one or more of:
at least 10% ergosterol;
ergosterol and β-sitosterol, wherein the ratio of ergosterol to β-sitosterol is greater than 25:1;
ergosterol and brassicasterol; and
ergosterol, brassicasterol, and poriferasterol.
11. The method of claim 10 , wherein the oil:
(a) forms β polymorph crystals; or
(b) wherein the oil forms β′ polymorph crystals.
12. The method of claim 10 , wherein:
(a) the triglycerides have a fatty acid profile characterized in that the sum of the percentage of stearate and palmitate is equal to the percentage of oleate multiplied by 2.0+/−40%;
(b) the oil has greater than 65% SOS triglycerides, less than 45% unsaturated fatty acid, less than 5% unsaturated fatty acids, less than 1% lauric acid, and less than 2% trans fatty acid;
(c) the sum of the percent stearate and palmitate in the fatty acid profile is twice the percentage of oleate, ±20%;
(d) the oil is at least 40, 50, 60, 70, 80, or 90% SOS; and/or
(e) the oil is a roll-in shortening having a melting temperature of between 30° C. and 40° C.
13. A method wherein the oil obtained by the method of claim 10 is used to produce a food, fuel or chemical product.
14. A nucleic acid construct, vector, chromosome or host cell comprising nucleic acids encoding a protein having at least 90% identity to SEQ ID NOs: 77 to 79 or having at least 95% identity or at least 98% identity to SEQ ID NOs: 77 to 79.
15. The nucleic acid construct, vector, chromosome, or host cell of claim 14 , comprising nucleic acids having at least 80, 90, 95, 96, 97, 98, or 99% sequence identity to SEQ ID NOs: 80-85 or equivalent sequences by virtue of the degeneracy of the genetic code.
16. The cell of claim 1 , wherein the cell comprises an exogenous sucrose invertase gene so that the cell can grow on sucrose as a sole carbon source.
17. The method of claim 10 , wherein the oil is free from one or more of β-sitosterol, campesterol, and stigmasterol.
18. The method of claim 11 , wherein the crystals have a 2L lamellae structure or a 3L lamellae structure.