Studies On The Propionic Acid Fermentation From Propionibaeterium Acidipropionici FS1026

According to the growth characteristic of Propionicbacterium and the chemical properties of propionic acid, a HPLC assay and an accurate screening method of strains with high production for propionic acid were built up successfully respectively. FS1026 with high production propionic acid was screened from market cheese. Through the physiological and biochemical examination and phylogenetic tree construction based on the 16s rDNA sequences, FS1026 was a strain of Propionibaeterium acidipropionici.First of all, by means of single factor test and response surface experiment the culture conditions optimization of FS1026 producing propionic acid were studied, the results showed, the culture time of seed was 72 h, the optimal temperature was 33℃, pH was 7.36, inoculum concentration was 10%, the volume of liquid was 150mL/250mL. The optimum fermentation culture medium was:glucose 56.62g/L, yeast powder 43.25g/L, peptone 7g/L, K2HPO424g/L, MgSO4 0.7g/L. The production of propionic acid reached 20.33g/L; the conversation rate of propionic acid was 35.91% in batch fermentation.Second, the immobilization fermentation of propionic acid with FS1026 cells immobilized by PVA-calcium alginate was studied. The researches included the immobilization conditions、culture conditions and stability of the immobilization fermentation. The results showed that the optimal concentration of PVA and sodium alginate was 10.8g/L and 1.5g/L respectively. The cells were immobilized in the stationary liquid containing calcium chloride (2%) and boric acid (50g/L) for 8h. The optimum culture medium was:glucose 75.41g/L, yeast powder 30g/L, peptone 16.31g/L, K2HPO4 24g/L, MgSO4 0.7g/L. The optimum method to feed glucose was that glucose concentration in liquid was added to 35g/L every 24 h.The production of propionic acid could up to 42.76g/L. The average production of propionic acid reached 26.31g/L in 10 batches of fermentation.A kind of novel immobilization material (Fe3O4 magnetic nanoparticles) was used as carrier. When the nanoparticles were modified by ammonium citrate, the fixed rate immobilized with FS1026 cells could reach 96.7%. The immobilization conditions, culture conditions and stability of the immobilization fermentation were investigated. The results showed that the optimum immobilized conditions were pH 4.5, fixed time 30min, the weight ratio of cells to Fe3O4 1:2.5, the weight ratio of Ammonium Citrate to Fe3O4 1:2.5. The optimal culture mediums were:glucose 75.53g/L, yeast powder 52.06g/L, peptone 7g/L, K2HPO4 24g/L, MgSO4 0.7g/L. The optimum method to feed glucose was that glucose concentration in liquid was added to 20g/L every 24 h. In the end the production of propionic acid could up to 37.5g/L. The average production of propionic acid was about 31.81g/L in 8 batches of fermentation, and there was still 28.30g/L level after 14 batches of fermentation.