초록
<P>The yeast Yarrowia lipolytica is able to produce high amounts of several organic acids such as pyruvic, citric, isocitric, alpha-ketoglutaric, and succinic acid. Here we report on the influence of the reduced activity of succinate dehydrogenase in Y. lipolytica on its ability to produce succinate. The recombinant strains Y. lipolytica H222-AZ1 and H222-AZ2 were created by exchange of the native promoter of the succinate dehydrogenase subunit 2 encoding gene by inducible promoters. During the cultivation of the strain Y. lipolytica H222-AZ1 in shaking flask experiments, it was found that the promoter exchange resulted in an increase in succinic acid (SA) production. Moreover, it was found that the production of SA depends on an additional limitation of oxygen. Fed-batch cultivations in 1-l bioreactors confirmed this fundamental finding. Y. lipolytica H222-AZ1 produced 2??g??l(-1) of SA with oxygen supply and 9.2??g??l(-1) under the limitation of oxygen after 165??h. By using a less active promoter in Y. lipolytica H222-AZ2, the production of SA was increased to 25??g??l(-1) with a productivity of 0.152??g???(l*h)(-1) and a selectivity of 67??% after 165??h. Yields of 2.39??g SA per gram biomass and 0.26??g SA per gram glycerol were found.</P>