Acetone/Butanol Fermentation Coupled With Pervaporation Separation Based On Hollow Fiber Membrane

In this paper, firstly, PDMS/PVDF hollow fiber composite membrane was prepared for recovery of acetone and butanol from dilute aqueous solutions. The effects of feed temperature, organics concentration and pH on pervaporation performance were investigated. The results indicate that, the composite membrane exhibites good performance for the separation of acetone, butanol and ethanol. At 40℃, the selectivity of actone, butanol and ethanol is 20.09,22.95 and 3.93, respectively,under nature pH.The screening of appropriate cassava was followed in this paper, and South China 205 cassava was selected as the raw material for this study. The results show that, during butanol batch fermentation coupled with pervaporation, the average and the largest productivity of total solvents are 0.68gL-1h-1 and 1.55gL-1h-1, increasing 41.7% and 44.9%, respectively. Acetone, butanol and the total solvent concentration in the penetrant are 50gL-1, 100gL-1 and 170gL-1, respectively. Comparing to batch fermentation without pervaporation, solvent concentration and starch utilization increase 123.9% and 69.3%, respectively.The hydrolysis conditions of tapioca were optimized and the results are as follows:the ratio of cassava and water is 1:1.5, the dosage of liquefaction enzyme is lOUg-1, and the high starch concentration cassava hydrolysate can be prepared after liquefied 60min under natural pH and 75℃.The fed mode, substrate concentration and separation coupled time during fermentation-separation process were also studied in this study when using cassava hydrolyzate as raw material. By continuous fed mode, controlling the total sugar concentration in fermentation broth at 60gL-1 and starting the pervaporation process when the butanol concentration in fermentation broth is 7gL-1,the higher productivity can be obtained during fed-batch fermentation-separation coupling operation.The fed-batch fermentation coupling pervaporation was researched in 5L fermenter. The average productivity of total solvents during the whole fermentation process is 0.62gL-1h-1 while during the feeding process is 0.9gL-1h-1, the maximum value is 1.33gL-1h-1. The total solvents and butanol concentration in the fermentation broth are under 11gL-1 and 6gL-1, respectively. While in the penetrant, the average total solvents and butanol concentration are 220gL-1 and 126.6gL-Therefore, the PDMS/PVDF hollow fiber composite membrane can separate and condence acetone, butanol and ethanol from aqueous solution effectively. ABE fermentation coupled with pervaporation process can reduce the inhibitory effect of butanol significantly, and improve the fermentationproductivty.