Abstract
BACKGROUND: Yarrowia lipolytica, one of the most charming chassis cells in synthetic biology, is unable to use xylose and cellodextrins. RESULTS: Herein, we present work to tackle for the first time the engineering of Y. lipolytica to produce lipids from cellodextrins and xylose by employing rational and combinatorial strategies. This includes constructing a cellodextrin-phosphorolytic Y. lipolytica by overexpressing Neurospora crassa cellodextrin transporter, Clostridium thermocellum cellobiose/cellodextrin phosphorylase and Saccharomyces cerevisiae phosphoglucomutase. The effect of glucose repression on xylose consumption was relieved by installing a xylose uptake facilitator combined with enhanced PPP pathway and increased cytoplasmic NADPH supply. Further enhancing lipid production and interrupting its consumption conferred the obese phenotype to the engineered yeast. The strain is able to co-ferment glucose, xylose and cellodextrins efficiently, achieving a similar μ(max) of 0.19 h(-1), a q(s) of 0.34 g-s/g-DCW/h and a Y(X/S) of 0.54 DCW-g/g-s on these substrates, and an accumulation of up to 40% of lipids on the sugar mixture and on wheat straw hydrolysate. CONCLUSIONS: Therefore, engineering Y. lipolytica capable of assimilating xylose and cellodextrins is a vital step towards a simultaneous saccharification and fermentation (SSF) process of LC biomass, allowing improved substrate conversion rate and reduced production cost due to low demand of external glucosidase.