| 1,3-Propanediol(1,3-PD)is an important chemical compound with wide range of applications.It is mainly used as a monomer for the synthesis of PTT.Nowadays,the main methods of producing 1,3-PD are chemical synthesis and microbial fermentation.Microbial production of 1,3-PD has attracted wide attentions as it uses renewable resources and dose not generate pollutants.In this paper,industrial raw glycerol was used as the substrate to produce 1,3-PD by Clostridium butyricum,in order to reduce the cost of 1,3-PD production.The contents of paper include fed-batch cultures progress optimization,metabolic evolution,scale-up fermentation and electrodialysis desalting.1.Fed-batch cultures were carried out by controlling the glycerol concentration under 20 g/L.The effects of inoculum rates,stirring speed,initial glycerol concentration and sterilization operation on fed-batch cultures were investigated.Results are as follows:(1)Increasing inoculum rates didn't affect the final concentration,yield and productivity of 1,3-PD;(2)Though increase the stirring speed could increase the biomass,it didn't affect the final concentration,yield and productivity of 1,3-PD.While the time of fed-batch cultures grew longer and reduced the productivity of 1,3-PD when without stirring.The productivity of 1,3-PD was 0.36 g/L/h merely.Therefore,the stirring speed of 100-150 rpm was the most suitable to fed-batch cultures.(3)Experiments showed that too high initial glycerol concentration was disadvantage to the biomass,or the generation of 1,3-PD.The results of initial glycerol concentration of about 45 g/L were the best.The final concentration and yield of 1,3-PD was 32.8 g/L and 0.44 g/g.What's more,sterilization or not had not obvious influence on Clostridium butyricum anaerobic fermentation system under stirring and nitrogen.2.Firstly,we obtained the stain Clostridium butyricum M80 through the metabolic evolution,which could tolerate up to 100 g/L of raw glycerol.As a result,the tolerance and growth efficiency of strains improved significantly.The fermentation time of M80 was shortened from 60 h to 43 h.And the biomass was enhanced from 2.4 g/L to 2.9 g/L.The concentration of 1,3-PD was enhanced from 32.8 g/L to 41.5 g/L.The productivity were improved from 0.55 g/L/h to 0.97 g/L/h.Secondly,the effects of increase glycerol concentration in feeding broth and temperature on fed-batch cultures were investigated.As a result,increase glycerol concentration in feeding broth could enhance 1,3-PD concentration from 41.5 g/L to 46.64 g/L.The results of fed-batch cultures indicated that reducing temperature could improve the 1,3-PD concentration a little,but the fermentation time of fed-batch culture grew longer and the productivity of 1,3-PD was reduced from 1.09 g/L/h to 0.88 g/L/h.3.Through investigate scale-up fermentation in 50 L fermentator basic on the fermentation progress of 5 L fermentator,we drew the conclusion that the results of 50 L fermentator were better than 5 L fermentator.Then,50 g/L of glycerol was used as the substrate to produce 1,3-PD by C.butyricum M80.The results of fed-batch cultures were that the concentration,yield and productivity of 1,3-PD were 59.36 g/L,0.53 g/g and 2.52 g/L/h,respectively.And the fermentation time was only 23.5 h.4.Firstly,the rates of cell and protein removing respectively were 99%? 98.1%by ceramic membrane and ultrafiltration.Secondly,the equipment of electrodialysis desalting was operated to test the performance of the salt removing effect in the ferment with different factors.The results indicated that the best operation voltage was 10 V and the best ratio of conductivity in dilute and concentrated compartment was 1:1.The results of electrodialysis indicated that the desalination rate of fermentation broth was above 99%and loss rate of 1,3-PD was 3.90%under these operating conditions. |
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