Redirecting the lipid metabolism of the yeast Starmerella bombicola from glycolipid to fatty acid production
Free fatty acids are basic oleochemicals implemented in a range of applications including surfactants, lubricants, paints, plastics, and cosmetics. Microbial fatty acid biosynthesis has gained much attention as it provides a sustainable alternative for petrol- and plant oil-derived chemicals. The yeast Starmerella bombicola is a microbial cell factory that naturally employs its powerful lipid metabolism for the production of the biodetergents sophorolipids (> 300 g/L). However, in this study we exploit the lipidic potential of S. bombicola and convert it from the glycolipid production platform into a free fatty acid cell factory. We used several metabolic engineering strategies to promote extracellular fatty acid accumulation which include blocking competing pathways (sophorolipid biosynthesis and β-oxidation) and preventing free fatty acid activation. The best producing mutant (Δcyp52m1Δfaa1Δmfe2) secreted 0.933 g/L (± 0.04) free fatty acids with a majority of C18:1 (43.8%) followed by C18:0 and C16:0 (40.0 and 13.2%, respectively). Interestingly, deletion of SbFaa1 in a strain still producing sophorolipids also resulted in 25% increased de novo sophorolipid synthesis (P = 0.0089) and when oil was supplemented to the same strain, a 50% increase in sophorolipid production was observed compared to the wild type (P = 0.03). We believe that our work is pivotal for the further development and exploration of S. bombicola as a platform for synthesis of environmentally friendly oleochemicals.
KeywordsStarmerella bombicola Yeast Free fatty acid Lipid metabolism Sophorolipid
This work was funded by the Strategic Basic Research from the Research Foundation Flanders (FWO), (Sylwia Jezierska PhD Grant Number 151610). We would like to thank the Centre for Advanced Light Microscopy at Ghent University (Belgium) for the use of the fluorescence microscope during BodiPy staining experiments. We would also like to thank the Laboratory for Animal Nutrition and Animal Product Quality (Lanupro) at Ghent University for FID-MS analysis. The authors would like to acknowledge Dries Duchi for the excellent technical support during HPLC and UPLC analysis. The authors have no conflict of interest to declare.
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