[Biosynthesis of isocitric acid by the yeast yarrowia lipolytica and its regulation].

We studied the biosynthesis of isocitric acid from rapeseed (canola) oil by the yeast Yarrowia lipolytica and its regulation. We determined a fundamental possibility for directed biosynthesis of isocitric acid by Y lipolytica yeast, with only minimal amounts of citric acid byproduct, when grown on a medium containing canola oil. Wild type strains of Y lipolytica were mutagenized by UV irradiation and treatment with N-methyl-N'-nitro-N-nitrosoguanidine (NG). Subsequent selection on media with acetate and isocitrate resulted in isolation of a UV/NG Y lipolytica UV/NG mutant that synthesized isocitrate and citrate at a ratio of 2.7:1. In the parent strain, this ratio is 1:1. Inhibition of isocitrate lyase, a key enzyme in the metabolism of isocitric acid, by the addition of itaconic acid resulted in increased synthesis of isocitrate with a ratio of isocitrate to citrate reaching 6:1. Culturing of the Y lipolytica UV/NG mutant in a pilot industrial fermenter in the presence of itaconic acid resulted in the production of 88.7 g/L of isocitric acid with a yield of 90%.