Enhancement of oxygen mass transfer in stirred bioreactors using oxygen-vectors 2. Propionibacterium shermanii broths.

The previous works on simulated broths are continued and developed for Propionibacterium shermanii broths. The obtained results indicated the considerable increase of kLa in presence of n-dodecane as oxygen-vector and the existence of a certain value of hydrocarbon concentration that corresponds to the maximum mass transfer rate of oxygen. The magnitude of the positive effect of the oxygen-vector strongly depends on operational conditions of the bioreactor, on broth characteristics and on P. shermanii concentration.

[Separation of vitamins by non-conventional techniques. Facilitated pertraction of vitamin C]. / Separarea vitaminelor prin procedee neconventionale pertractia facilitata a vitaminei C.

Pertraction (permeation through liquid membranes) is one of the new techniques applied for separation and advanced purification of bioactive compounds. The study on the facilitated pertraction of vitamin C with Amberlite LA-2 underlined the significant influences of the pH-gradient between the aqueous phases, carrier concentration and mixing intensity. Thus, for reaching the maximum efficiency of vitamin C pertraction, the pH-value of the initial aqueous phase below 2, the pH-value of the final aqueous solution greater than 11 and the Amberlite LA-2 concentration in solvent layer over 80 g/l are required.