A metabolic engineering approach to increase lipid accumulation in yeast grown on glycerol
It was recently demonstrated that the yeast Yarrowia lipolytica , is capable of growing on industrial glycerol, a byproduct of biodiesel production, and converting it into large amounts of intracellular lipid particles. Yeast lipids could serve as a potential source for additional biodiesel production. This research explored the effects of enhanced cytoplasmic glycerol 3-phosphate dehydrogenase activity on lipid accumulation during growth on glycerol. Cytoplasmic glycerol 3-phosphate dehydrogenase catalyzes the reaction between dihydroxyacetone phosphate and glycerol 3-phosphate. Glycerol 3-phosphate serves as a precursor for triacylglyceride synthesis and was recently demonstrated to be a key metabolite in lipid accumulation. The continuous fermentation reactor was performed under nitrogen limiting conditions to induce lipid storage. A low dilution rate (0.04 hr-1) was employed for optimal cell mass accumulation and nitrogen exhaustion. The system was agitated, aerated (1.8 L-air L-medium -1 min-1), isothermal (28°C), with constant pH (6.00). At steady-state conditions the wild-type strain reached an average value of 2.70 g L-1 dry mass with 1.12 g L -1 lipid mass. The modified strain with enhanced glycerol 3-phsophate dehydrogenase activity reached an average value of 2.75 g L-1 dry mass with 1.11g L-1 lipid mass. These values are not statistical significantly different and suggest enhanced cytoplasmic glycerol 3-phosphate dehydrogenase activity does not have an affect lipid accumulation in this system. ^
Bernard Y. Tao, Purdue University.