The nutritive values o f propionic acid bacteria (Pb) grown in whey media as mixed cultures and as a 2-stage fermentation with a lactosefermenting yeast (Y-Pb) were determined. Yields were 14 g o f cells per liter f o r Pb cultures and 16 g/liter for Y-Pb fermentations. When the fermentation medium and cells were dried together, total solids equalled 28 glliter. The BOD of the whey was reduced over 90% in both fermentations. Adequate yields o f vitamins, particularly B1 , were obtained in both fermentations. The in vitro enzymatic digestibility of the cultures was increased by mechanical disruption o f cells; however, this cell breakage did not affect Biological Value (BV). The essential amino acid composition was equal to or better than the F A 0 Standard Reference Protein. The BV o f the Y-Pb was 25% higher than Pb and 10-40% higher than other microbial cell masses, including Torula yeast, commercial yeast and BP yeast from n-para f f in.

Summary -Cobalt occurs in nature usually at very low concentrations and is accompanied by much higher concentrations of various metals. In order to acquire cobalt under such unfavorable conditions, living systems evolved effective uptake mechanisms based on high affinity to cobalt and distinguishing this element from among the others. Taking Propionibacterium arabinosum as the bacterial rnodel, which is known for its cobalt requirement, the performance of microorganisms has been examined in this regard. By using radiolabeled cobalt and a filter technique, the uptake capability of these bacteria at the stage of cobalt binding has been characterized in terms of binding capacity, and dissociation and equilibrium constants. Monovalent and divalent ions inhibit cobalt binding to bacteria. Divalent metal ions showed a competitive mode of inhibition, and the inhibitory constants for some of the toxic and biologically important divalent metal ions were determined. The chelating agent EDT A diminishes cobalt binding to bacteria already at concentration 10-5 Ilmoi/i. Bacteria

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