Delta-9 fatty acid desaturase overexpression enhanced lipid production and oleic acid content in Rhodosporidium toruloides for preferable yeast lipid production.

The oil plants provide a sufficient source of renewable lipid production for alternative fuel and chemical supplies as an alternative to the depleting fossil source, but the environmental effect from these plants' cropping is a concern. The high oleic acid (OA; C18:1) content in plant-derived products provide advantages of multiple uses with improved oxidative stability and a wide range of applicable temperature. Here we used a promising lipid producer, the oleaginous yeast Rhodosporidium toruloides, to attempt to obtain an OA-enriched lipid. Saccharomyces cerevisiae OLE1 (ScOLE1) gene encodes Δ9 fatty acid desaturase (Δ9FAD), which is generally known to synthesize palmitoleic acid (POA; C16:1) and OA, but the functions of putative R. toruloides Δ9FAD gene are not well understood. In a complementary test, the RtΔ9FAD gene rescued the survival of an OA-deficient Scole1Δ mutant, and we introduced the RtΔ9FAD gene into R. toruloides strains for the production of OA-enriched lipid. Increasing lipid production was observed in ScOLE1 and genomic RtΔ9FAD gene-overexpressing R. toruloides strains. The ScOLE1 transformant output fivefold more OA content in total amount, with >70% of total lipid. Different enhancing effects from the protein coding sequence and genomic sequence of RtΔ9FAD genes were also observed. Overall, this study resulted in ScOLE1 and RtΔ9FAD gene overexpression in R. toruloides to obtain OA-enriched lipid as a candidate source of designed biodiesel and lipid-related chemicals.