[Isolation of cobalt-resistant strains of propionic acid bacteria, potent producers of vitamin B12].

A method of adaptation to cobalt nitrate at high concentrations allowed us to isolate 46 strains of propionic acid bacteria Propionibacterium acidipropionici, resistant to excessive amounts of Co2+ in the medium. Studies of these strains revealed cultures that were most potent in synthesizing vitamin B12. The yield of vitamin B12 was increased 3 times, compared to parent strains.

[NAD-metabolizing capacity of Saccharomyces cerevisiae mutants].

The activity of the key enzymes of the salvage synthesis and degradation of NAD (nicotinic acid mononucleotide pyrophosphorylase and NAD glycohydrolase) was studied in Saccharomyces cerevisiae mutants selected earlier as potential producers of NAD. An enhanced NAD-producing ability of the mutants was shown to be related to their reduced NAD-degrading activity: thus, NAD glycohydrolase in mutants 110, 118, and 206 was inactive in all growth phases regardless of the level of NAD biosynthesis.