Studies On Effect Of Yeast Powder And Influence Of Nitrogen Source On Riboflavin Fermentation By Bacillus Subtilis 24/pMX45

This work mainly study on the effects of yeast powder and its components on the Bacillus subtilis 24/pMX45 riboflavin fermentation, the relation between nitrogen source and riboflavin fermentation, the influence of composite nitrogen source and inorganic ions on riboflavin fermentation, and discuss the optimize of the kind of nitrogen source and its supply.Inoculation with fresh lawn is more efficient in investigating the rule of riboflavin shake-flask fermentation than with seed solution, it can reduce the steps and avoid the disturbances of seed factor on fermentation.During the fermentation of Bacillus subtilis 24/pMX45, yeast powder provide nitrogen source for cell growth and riboflavin production, supply growth factor to cell. Something of dissolvable substance has no advantage for riboflavin production in yeast powder because it can induce Carbon Catabolite Repression and overflow metabolic. Glu is 57.87% in proportion to all 17 kinds of amino acid in yeast powder. When the concentration of Glu in the culture is beyond 800mg/l, it promotes glucose consuming, induce overflow metabolic and has no advantage to producing riboflavin. So enhancing yeast concentration will enhancing the concentration of Glu, will have harm to riboflavin production.It is not enough that use 2.5% yeast powder as nitrogen source in riboflavin fermentation. Adding inorganic nitrogen source such as NH4Cl,(NH4)2SO4 to culture medium , increase glucose concentration and Carbon Catabolite Repression and have no benefit to riboflavin production. Adding 0.2% urea to 2.5% yeast powder as nitrogen source can promote 20 percent of riboflavin production. To enhance riboflavin production, the urea concentration should below 2000mg/l and maintain long time. Adding Zn2+ or Mn2+ to culture medium is of benefit to riboflavin producing. But adding urea and Zn2+ or Mn2+, the promotion of riboflavin production disappears.