Yeast is, above all, a single-celled fungus — and some of its genetically modified strains already operate as tiny refineries capable of converting sugar into molecules almost identical to petroleum-derived aviation fuels. Metabolic engineering of yeast has become one of the most promising routes to bio-based fuel.
The problem of toxicity
Monoterpenes — compounds with physical properties similar to those of Jet-A aviation fuel — are toxic to the very yeast that produces them. Researchers determined the minimum inhibitory concentrations for five monoterpenes in Saccharomyces cerevisiae and developed a two-phase extractive fermentation system that reduced toxicity by up to 700 times for some compounds, allowing for viable industrial-scale fermentations.
From used cooking oil to aviation fuel
Another study designed a biosynthetic pathway in the oleaginous yeast Yarrowia lipolytica to produce alpha-pinene — a monoterpene with high energy density used in renewable fuels — achieving a 218-fold improvement over the initial yield. Notably, the strain produced alpha-pinene using waste cooking oil and lignocellulosic hydrolysate as carbon sources, instead of cane or corn sugar.
What's at stake
Aviation is one of the most difficult sectors to decarbonize: there is no viable electric alternative yet for long-haul flights. Fuels derived from modified yeasts, produced from agricultural or kitchen waste, offer a realistic way to reduce dependence on fossil fuels without completely redesigning existing aeronautical infrastructure.
References
- Brennan TCR, Turner CD, Krömer JO, Nielsen LK. Alleviating monoterpene toxicity using a two-phase extractive fermentation for the bioproduction of jet fuel mixtures in Saccharomyces cerevisiae. Biotechnol Bioeng. 2012;109(10):2513-2522. PMID: 22539043. DOI: 10.1002/bit.24536
- Wei LJ, Zhong YT, Nie MY, Liu SC, Hua Q. Biosynthesis of alpha-Pinene by Genetically Engineered Yarrowia lipolytica from Low-Cost Renewable Feedstocks. J Agric Food Chem. 2021;69(1):275-285. PMID: 33356235. DOI: 10.1021/acs.jafc.0c06504