Role of pyruvate carboxylase in accumulation of intracellular lipid of the oleaginous yeast Yarrowia lipolytica ACA-DC 50109

Yarrowia lipolytica ACA-DC 50109 is an oleaginous yeast. In order to know the function of pyruvate carboxylase (PYC) in lipid biosynthesis, the PYC gene cloned from Pichia guilliermondii Pcla22 was overexpressed in the oleaginous yeast. The lipid contents in the wild-type strain ACA-DC 50109 and the transformants P4, P7, and P103 were 30.2 % (w/w) 36.5 % (w/w), 38.2 % (w/w), and 37.9 % (w/w). However, the amount of the secreted citric acids by strains ACA-DC 50109, P4, P77, and P103 were 0.5, 10.1, 11.5, and 9.4 g/L. In order to reduce the amount of the secreted citric acid, the PYC gene and endogenous ACL1 gene encoding ATP citrate lyase (ACL1) were simultaneously overexpressed in the oleaginous yeast. The lipid contents of the transformants PA19, PA56, PA124 were 44.4 % (w/w), 45.3 % (w/w), and 43.7 % (w/w). At the same time, the amount of the secreted citric acid by the transformants PA19, PA56, and PA124 was reduced to 5.4, 6.2, and 6.3 g/L. The PYC and ACL1 activities and their gene transcriptional levels in all the transformants were greatly enhanced compared to those in their wild-type strain ACA-DC 50109. During 10-L fermentation, lipid content in the transformant PA56 was 49.6 % (w/w) and the amount of secreted citric acid was 2.9 g/L. This meant that PYC and ACL1 can play an important role in accumulation of intracellular lipid of the oleaginous yeast Y. lipolytica ACA-DC 50109.