[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%.

[Study of genetic control of pediocins synthesis].

Plasmid profiles of 2 strains of Pediococcus acidilactici and 3 strains of P. pentosaceus were studied. Synthesis of bacteriocins in 2 strains of P. acidilactici was coded on the plasmid which was confirmed by experiment with elimination of plasmids and subsequent electrophoregram, which demonstrated synchronous disappearance of bacteriocins synthesis characteristic in plasmid-lacking variants. In 3 strains of P. pentosaceus plasmids were not found which points to chromosomal localization of genes for bacteriocins production.