Down-regulation of a polynucleotide encoding a Sou2 sorbitol utilization protein to modify lipid production in microbial cells

1. A recombinant microbial cell comprising:

(i) a down-regulation of an endogenous polynucleotide sequence encoding Sou2 sorbitol utilization protein comprising the amino acid sequence of an Sou2 sorbitol utilization protein selected from the group consisting of Asperqillus niger, Bifidobacterium dentium, Candida albicans, Candida dubliniensis, Candida orthopsilosis, Candida parapsilosis, Cordyceps militaris, Debaryomyces hansenii, Enterobacter hormaechei, Gaeumannomvces graminis, Glarea lozovensis, Lodderomyces elonqisporus, Maqnaporthe oryzae, Metarhizium acridum, Metarhizium anisopliae, Mycobacterium smeqmatis, Neurospora crassa, Neurospora tetrasperma, Paracoccidioides brasiliensis, Penicillium chrysoqenum, Scheffersomvces stipitis, Uncinocarpus reesii, Verticillium dahliae , and Yarrowia lipolytica , and

(ii) a polyunsaturated fatty acid (PUFA) biosynthetic pathway, wherein said down-regulation increases the lipid content of the microbial cell and/or decreases the total amount of sugar alcohols produced by the microbial cell, as compared to a suitable control cell.

2. The recombinant microbial cell of claim 1 , wherein said down-regulation is due to a mutation of said endogenous polynucleotide sequence.

3. The recombinant microbial cell of claim 2 , wherein said mutation is selected from the group consisting of a substitution, deletion and insertion.

4. The recombinant microbial cell of claim 3 , wherein said mutation is a deletion that removes

(i) one or more nucleotides from an open reading frame encoding said Sou2 sorbitol utilization protein, and/or

(ii) one or more nucleotides of a non-protein-coding sequence located within 500 base pairs of the 5′-end of said open reading frame.

5. The recombinant microbial cell of claim 3 , wherein said mutation is an insertion that occurs within

(i) an open reading frame encoding said Sou2 sorbitol utilization protein, or

(ii) a non-protein-coding sequence located within 500 base pairs of the 5′-end of said open reading frame.

6. The recombinant microbial cell of claim 1 , wherein said PUFA pathway produces at least one PUFA selected from the group consisting of linoleic acid, alpha-linolenic acid, gamma-linolenic acid, stearidonic acid, eicosadienoic acid, dihomo-gamma-linolenic acid, arachidonic acid, eicosatrienoic acid, eicosatetraenoic acid, eicosapentaenoic acid, docosatetraenoic acid, omega-3 docosapentaenoic acid, omega-6 docosapentaenoic acid and docosahexaenoic acid.

7. The recombinant microbial cell of claim 6 , wherein said PUFA pathway produces eicosapentaenoic acid.

8. The recombinant microbial cell of claim 1 , wherein said sugar alcohols comprise arabitol or mannitol.

9. The recombinant microbial cell of claim 1 , wherein said microbial cell is an oleaginous yeast cell.

10. The recombinant microbial cell of claim 9 , wherein said oleaginous yeast is a Yarrowia lipolytica cell.

11. The recombinant microbial cell of claim 10 , wherein the Sou2 sorbitol utilization protein comprises the amino acid sequence set forth in SEQ ID NO:10.

12. The recombinant microbial cell of claim 10 , wherein said endogenous polynucleotide sequence comprises the nucleotide sequence set forth in SEQ ID NO:9.

13. A method of producing a microbial oil comprising a polyunsaturated fatty acid (PUFA), said method comprising:

a) culturing the recombinant microbial cell of claim 1 , wherein a microbial oil comprising a PUFA is produced; and

b) optionally recovering the microbial oil of step (a).

14. The method of claim 13 , wherein the microbial oil comprises eicosapentaenoic acid.