Engineered yeast Yarrowia lipolytica as a chassis for biosynthesis of fatty acids from mannitol and macroalgal biomass extracts.

BACKGROUND

Yarrowia lipolytica possesses the capability to utilize many unconventional carbon sources, such as crude glycerol, alkanes and fatty acids. Despite producing polyols, such as erythritol, arabitol and mannitol, the re-utilization of mannitol is not as efficient as erythritol utilization. Genes involved in mannitol uptake and metabolism in Y. lipolytica remain undescribed. However, deletion of the EYD1 gene (YALI0F01650g), believed to encode erythritol dehydrogenase, has been found to result in a high rate of growth on media containing mannitol as the sole carbon source. Therefore this unique feature was used for further fermentation studies on media containing macroalgal mannitol extracts, obtained from the brown alga Fucus vesiculosus, to produce value-added products.

RESULTS

The obtained strain AJD Δeyd1Dga1 was able to uptake pure and algal mannitol efficiently and produce high amounts of lipids, thanks to overexpression of the DGA1 gene (YALI0E32769g), encoding diacylglycerol (DAG) acyltransferase. The lipid content reached almost 32% of the overall dry biomass as compared to the wild type strain, where this value was more than 4 times lower. Additionally, the biomass at the end of the experiment was the highest among all of the tested strains, reaching 12.67 g/L, more than 50% higher than the control strain.

CONCLUSIONS

The results of this study shed new light on the potential for the yeast Y. lipolytica to utilize macroalgae biomass as a carbon source for production of value-added products, including biomass and lipids. Moreover, the increased mannitol utilization capabilities can provide new insight into mannitol metabolism, including its uptake, which is especially crucial, as the metabolic pathways for all polyols produced by this organism seem to be closely intertwined.