In this work, we analysed the efficiency of xylose consumption and lipid production in three recombinant strains of Y. lipolytica, bearing the isomerase pathway, the reductase pathways, or both at the same time, at laboratory bioreactor scale: The strain with the isomerase pathway showed higher intracellular lipid accumulation when oxygen levels were limited. The strain with the xylose reductase pathway showed the highest overall yield, producing 12.8 g/L lipids (43% of dry weight) and 0.13 g lipid/g xylose. The strain combining both pathways was less effective than the strain with the xylose reductase pathway alone.
ABSTRACT
Xylose is a common monosaccharide in lignocellulosic residues that Yarrowia lipolytica cannot naturally metabolise for lipid production and therefore, heterologous xylose metabolic pathways must be engineered in this yeast to facilitate its consumption. We have compared the metabolic efficiency of two xylose metabolic pathways by developing three recombinant Y. lipolytica strains: one harbouring a xylose reductase pathway, one with a xylose isomerase pathway, and one combining both pathways, and the strains were tested for xylose consumption and lipid production at different scales. The recombinant strain with the reductase pathway that was directly isolated in selective xylose medium showed the highest lipid yield, producing up to 12.8 g/L of lipids, or 43% of the biomass dry weight, without requiring any other xylose consumption adaptive evolution process. This strain achieved a lipid yield of 0.13 g lipids/g xylose, one of the highest yields in yeast reported so far using xylose as the sole carbon and energy source. Although the strain harbouring the isomerase pathway performed better under oxygen-limiting conditions and led to higher lipid intracellular accumulation, it showed a lower xylose uptake and biomass production, rendering a lower yield under non-limiting oxygen conditions. Unexpectedly, the combination of both pathways in the same strain was less effective than the use of the reductase pathway alone.
Microbial Biotechnology, Volume 18, Issue 3, March 2025. Read More
