Pushing the Boundaries of Biofuels and Oleochemicals Production in Oleaginous Yeasts

Authors: 

Pushing the boundaries of biofuels and oleochemicals production in oleaginous yeasts

Rodrigo Ledesma-Amaro1,2 and Jean-Marc Nicaud1,2

rodrigo.ledesma@grignon.inra.fr

1INRA, UMR1319, MICALIS, Domaine de Vilvert, F-78352 Jouy-en-Josas, France 2AgroParisTech, UMR Micalis, Jouy-en-Josas, France

Microbial oils have emerged as promising alternatives to fossil oils, with substantial advantages over plant, animal and algae oils. Among the oleaginous microorganisms, Yarrowia lipolytica is by far the most studied and used by the industry. Additionally, in the last years, the natural capacity of this yeast to produced lipids has been maximized by sequential metabolic engineering approaches and culture optimization. Nonetheless, the cost of the process still limits its industrial production to high value compounds and therefore, more research is required to reduce these costs. Our lab is facing this issue by two independent and combinable approaches; expanding the usage of non-expensive substrates and improving lipid production by strain engineering. Both strategies are based on the use of metabolic engineering, synthetic biology, systems biology, metabolic modelling and process optimization techniques.

On the one hand, although Y. lipolytica can perfectly grow and produce lipids from glucose it is inefficient or incapable of using other preferred non-expensive carbon sources. We used metabolic engineering to expand the range of use of different hexoses, pentoses or polymeric sugars. The construction of this “Swiss army knife” is a combination of heterologous pathways expression and the awakening of endogenous and limiting sleeping genes. Some of these desired carbon sources are starch and lignocellulosic materials, which are inexpensive and widely spread in both nature and wastes. Therefore, we engineered Y. lipolytica to cope with these and other sugars. The results of these metabolic engineering approaches will be discussed.

On the other hand, we have combined previously known target with novel modifications in order to boost lipid accumulation. Additionally we identified the most favourable bioreactor conditions to maximize lipid production. We have recently achieved the highest lipid content described so far in a strain able to accumulate more than 90% of the DCW as lipids. The strategies leading to these strains will be presented and discussed.

The increasing researches in using microbial lipids to produce fuels and chemicals are spreading world wide in the last years, both in public and private sector, pointing out to a general interest and desire. This combined global effort brings us to a future independent of the undesired, limited, and pollutant fossil fuels.