Bio-lipid production from lignocellulose hydrolysate by the oleaginous yeast Lipomyces starkeyi

Considering the limitation of fossil raw materials utilization of renewable resources for fuel and chemicals production is required. Biofuel production should be sustainable and not compete with food and feed production. Lignocellulose is the most abundant biomass resource on earth and its hydrolysates are commonly esteemed as promising substrates for biofuel production.

Many oleaginous yeasts are able to convert carbon sources present in lignocellulose material to lipids under nitrogen limitation. The hemicellulose fraction contains mainly xylose and is therefore, difficult to convert to bioethanol. In addition, its low content of nitrogen is advantageous for lipid accumulation. On the other hand a variety of inhibitors is present, which can suppress growth completely. Starting with a model substrate we established feeding strategies with several feeding pulses and continuous feeding to keep the level of inhibitors on a suitable level. Using the continuous feeding we were able to grow Lipomyces starkeyi on birch hydrolysate and reach an intracellular lipid content of more than forty percent, about 8g/L lipid with a yield per g consumed xylose of 0.12. The degree of saturation was higher in fatty acids extracted from lipid accumulation cells in a late stage of cultivation.