OPTIMIZATION OF A PROPIONIBACTERIUM-ACIDIPROPIONICI CONTINUOUS-CULTURE UTILIZING SUCROSE

To produce propionic acid and vitamin B-12 from sucrose, the strain Pr opionibacterium acidipropionici NRRL B3569 was selected by screening a number of Propionibacterium strains. The nutrient composition and the fermentation conditions for this strain were optimized in continuous culture. The investigations show that within a concentration range of 30-170 g l(-1) of sucrose in the fermentation medium, no significant s ubstrate inhibition occurred. For the production of propionic acid and vitamin B-12, concentrations of 1.5 mg FeSO4 . 7H(2)O g(-1) dry bioma ss, 0.75 mg cobalt ions g(-1) dry biomass, 0.3 mg 5,6-dimethylbenzimid azole g(-1) dry biomass, and 12 g yeast extract l(-1) were necessary a dditions to the sources of nitrogen, phosphate, and magnesium ions. Th e extra addition of up to 2.8 g betaine g(-1) dry biomass significantl y increases the production of vitamin B-12. In the optimization of the pH value, temperature, and aeration, it was established that the cond itions for propionic acid production and vitamin B,, production are di fferent. Whereas the optimal production of propionic acid took place u nder completely anaerobic conditions with a pH value of 6.5 and a temp erature of 37 degrees C, optimal vitamin B-12 production required a te mperature of 40 degrees C and aerobic conditions (0.5 vvm aeration at 100 rpm) with a pH value of 6.5.