Study On The New Technics Of Citric Acid Production

Using Aspergillus niger Wsy which preserved in lab as original strain breeded a high citric acid producing strain Wsy-03.In flask fermenter,observed the mycelium pellet change of high citric acid producing strain Wsy-03 and low citric acid producing strain Wsy-01.Proved the co -nclusion that the higher Aspergillus niger producted citric acid the small mycelium pellet it was.At the same time,the author observed that as fermented the mycelium pellet winded more loose.And proved that if we used spore to inoculate the fermentation period wold be prolong.In the article,drawed the growth cures of Aspergillus niger.And pass to experiment the research,choosed the best timing of inoculation.In flask fermenter,detemined the best fermentation medium:18% of initial sugar in batch fermentation,added 17% unfiltered cornmeal liquid in order to complement nitrogen,and added 0.3% (NH₄)₂SO₄.Detemined the best fermentation medium of fed -batch fermentation was 14% of initial sugar.Pass to experiment the research,detemined the best fermentation medium situation:the most fitting fermentation temperature 35℃,the most fitting fermentation pH4.5,the most fitting fermentation inoculum size 10%.In 10L automatic fermention, detemined the best fermentation ven-tilation quantity:0²4h:0.12vvm,24⁷2h:0.15vvm.With the optimized fermentation situateio n,Aspergillus niger Wsy-03 citric acid yield was 13.99%,invert rate was 89.91%.Based on the optimized batch-fermentation condition,researched the best fed-batch fermentation situation:fed medium at 24h and 48h,added 0.3% (NH₄)₂SO₄ in glucose solution,the best fed batch fermentation is 3% glucose solution.In flask fermenter, Aspergillus niger Wsy-03 citric acid yield was 16.33%, incubation time was 65h, invert rate was 89.91%.The incubation time was 5h shorter than flask fermenter.