Towards a Microbial Production of Fatty Acids as Precursors of Biokerosene from Glucose and Xylose

Abstract

The aviation industry considers the development of sustainable biofuelsas one of the biggest challenges of the next ten years. The aim is tolower the environmental impact of the steadily increasing use of fossilfuels on climate change, yielding greater energy independence and fuelsecurity. Thus, the development of a new route for the production oflipids from renewable non-food resources is now being promoted with therecent ASTM certification of hydrotreated oils. Our study focuses on thepotential of growth of the oleaginous yeast Rhodotorula glutinis usingglucose and xylose which can come from renewable lignocellulosicsubstrates and of lipid accumulation using glucose as substrate.Experiments were carried out in fed-batch mode which allowed feed fluxmanagement. Carbon fluxes were controlled with modifying xylose/glucoseratios to quantify metabolism in optimal growth condition. Besides, themanagement of carbon and nitrogen fluxes allowed characterizing lipidaccumulation. Thus, it has been shown that the yeast Rhodotorulaglutinis can simultaneously consume glucose and xylose. When the ratioxylose/glucose increased, the growth rate and the carbon conversionyield into biomass decreased: it was of 0.36 h(-1) and 0.64 C-mol(X{*}).C-mol (-1)(glu) for pure glucose, it was of 0.15 h(-1) and 0.56C-mol.C-mol(-1) for 10% xylose and it was of 0.037 h(-1) and 0.18C-mol.C-mol(-1) for pure xylose. The necessity to maintain residualgrowth and to manage carbon fluxes to optimize lipid accumulationperformance was revealed. Lipid accumulation on glucose engendered afinal biomass concentration of 150 g(CDW).L-1, microbial production(72% of lipids) and maximal productivity over 1.48 g(lip).L-1.h(-1).The culture temperature is an important parameter to modulate the lipidprofile. The results were encouraging. Lipid accumulation usinglignocellulosic feedstock was shown to be a highly promising route.