Study On Continuous Butanol Fermentation Of Immobilization

Butanol has been regarded as an advanced bio fuel. As a substitute for petroleum fuel, butanol has a higher energy density than ethanol, and better compatibility with gasoline. The biggest problem of biobutanol production is the low butanol yield and productivity because of the inhibiton of butanol production. One of the methods to solve the problem is to establish multiple stage continuous fermentation system. And coupling continuous fermentation system with membrane separation technique could provide a high productivity and relieve the product inhibition.In this study, the focus on building an efficient continuous fermentation system integrated with membrane separation technique to improve the efficiency of butanol production. The three-stage continuous fermentation system and the membrane separation technique was studied before the integrated process is completed. On the basis of above works, the following are details:(1) The technique of the immobilized cell has been used in three-stage continuous ABE fermentation. The sugar concentration of feed supplement and dilution rate has been optimized.13 g·L-1 bio-butanol and 20 g·L-1 ABE were yield with 80 g·L-1 sugar in the feed supp;ement at a dilute rate of 0.12·h-1. And～12.5 g·L-1 butanol and～20.5 g·L- total ABE solvents were yield on conditions of operation at 0.16·h-1. The butanol space-time yield is 1.56 g-(L·h)-1 and the ABE yield is 2.4 g·(L·h)-1 (the previous is 0.97 g-(L·h)-1). The sugar into butanol conversion rate is 0.22g/g.(2) In the pervaporation process,40wt% bio-butanol is get from the 1.5wt% butanol when the feed temperature was 55℃. And the acetone concentration of ABE solution will inhibit the butanol separation.(3) A novel gas stripping assisted vapor permeation (GSVP) process was established. The impacts of the feed temperature and membrane temperature with feed concentration of the GSVP process were evaluated. In general, the feed temperature was the key factors.35wt% bio-butanol is get from 1.5wt% ABE(acetone:butanol:ethanot=3:6:1) when the feed temperature was 35℃.(4) A new process of single-stage continuous ABE fermentation in the immobilized cell mode coupled with GSVP was established. The butanol concentration on the permeate side was approximate 200～280 g·L-1, and the ABE concentration was 400～550 g·L-1.