Abstract: The invention relates to a process for the conversion of corrinoids produced by microorganisms into cyanocorrinoids by reaction with cyanides. According to the invention a fermentation broth obtained by disruption of microorganism cells in a known manner, preferably by heat treatment in the presence or absence of sulfite ions, optionally after purification steps known per se, is contacted with a suitable adsorbent or ion exchange resin, the corrinoids adsorbed on the surface of the adsorbent or ion exchange resin are treated with an aqueous solution containing cyanide ions or a compound capable of supplying cyanide ions, in an amount providing cyanide ions in a 1.1 to 2.0-fold molar excess related to the corrinoids, the adsorbent or ion exchange resin is washed with water, and the cyanocorrinoids obtained is eluted in a known manner, preferably with aqueous ethanol.

Abstract: A process is disclosed for the treatment of fermentation broths containing vitamin B.sub.12 and other corrinoids, and for the preparation of vitamin B.sub.12 concentrates or crystalline vitamin B.sub.12 wherein the fermentation broth is contacted with a nonionic, macroreticular, adsorption resin having a pore size of 10.sup.-8 to 10.sup.-7 meters, a grain diameter of at least 10.sup.-4 m, and a specific surface area of at least 200 m.sup.2 /g so that the macromolecular adsorption resin adsorbs fermentation broth additives and metabolites of fermentation, whereas the intact microorganism cells containing the vitamin B.sub.12 remain in solution. The solution of intact vitamin B.sub.12 -containing cells is then treated further to obtain vitamin B.sub.12 in still purer form.