Metabolic engineering of oleaginous yeast in the lipogenic phase enhances production of nervonic acid

Insufficient biosynthesis efficiency during the lipogenic phase can be a major obstacle to engineering oleaginous yeasts to overproduce very long-chain fatty acids (VLCFAs). Taking nervonic acid (NA, C24:1) as an example, we overcame the bottleneck to overproduce NA in an engineered Rhodosporidium toruloides by improving the biosynthesis of VLCFAs during the lipogenic phase. First, evaluating the catalytic preferences of three plantderived ketoacyl-CoA synthases (KCSs) rationally guided reconstructing an efficient NA biosynthetic pathway in R. toruloides. More importantly, a genome-wide transcriptional analysis endowed clues to strengthen the fatty acid elongation (FAE) module and identify/use lipogenic phase-activated promoter, collectively addressing the stagnation of NA accumulation during the lipogenic phase. The best-designed strain exhibited a high NA content (as the major component in total fatty acid [TFA], 46.3%) and produced a titer of 44.2 g/L in a 5 L bioreactor. The strategy developed here provides an engineering framework to establish the microbial process of producing valuable VLCFAs in oleaginous yeasts.

Automated summary

Insufficient biosynthesis efficiency during the lipogenic phase is a major obstacle to overproducing very long-chain fatty acids. This study successfully engineered an oleaginous yeast to overproduce nervonic acid by improving the biosynthesis of very long-chain fatty acids during the lipogenic phase. By evaluating different ketoacyl-CoA synthases and conducting a genome-wide transcriptional analysis, the researchers were able to optimize the biosynthetic pathway and overcome the bottleneck of fatty acid accumulation. The engineered strain achieved high levels of nervonic acid production.