Genetically engineered Escherichia coli FBR5: part II. Ethanol production from xylose and simultaneous product...

In these studies, concentrated xylose solution was fermented to ethanol using Escherichia coli FBR5 which can ferment both lignocellulosic sugars (hexoses and pentoses). E. coli FBR5 can produce 40-50 g L(-1) ethanol from 100 g L(-1) xylose in batch reactors. Increasing sugar concentration beyond this level results in the loss of sugar with the reactor effluent thus affecting the process yield adversely. In a nonintegrated system without simultaneous product removal more than 120 g L(-1) xylose was left unused of the 220 g L(-1) that was fed into the reactor. In contrast to this, application of simultaneous product removal by gas stripping was able to relieve product inhibition and the culture was able to use 216.6 g L(-1) xylose thus producing 140 g L(-1) (based on reactor volume) ethanol resulting in a product yield of 0.48. The product stream achieved an ethanol concentration up to 148.41 g L(-1). This process has potential for greatly improving the performance of E. coli FBR5 where the strain can ferment all the lignocellulosic sugars to ethanol and gas stripping can be applied to recover product.