Search

Clostridium spp. produce n-butanol in the acetone/butanol/ethanol process. For sustainable industrial scale butanol production, a number of obstacles need to be addressed including choice of feedstock, the low product yield, toxicity to production strain, multiple-end products and downstream processing of alcohol mixtures. This review describes the use of lignocellulosic feedstocks, bioprocess and metabolic engineering, downstream processing and catalytic refining of n-butanol.

SO2-ethanol-water (SEW) spent liquor from spruce chips was successfully used for batch and continuous production of acetone, butanol and ethanol (ABE). Initially, batch experiments were performed using spent liquor to check the suitability for production of ABE. Maximum concentration of total ABE was found to be 8.79 g/l using 4-fold diluted SEW liquor supplemented with 35 g/l of glucose. The effect of dilution rate on solvent production, productivity and yield was studied in column reactor consisting of immobilized Clostridium acetobutylicum DSM 792 on wood pulp. Total solvent concentration of 12 g/l was obtained at a dilution rate of 0.21 h(-1). The maximum solvent productivity (4.86 g/l h) with yield of 0.27 g/g was obtained at dilution rate of 0.64 h(-1). Further, to increase the solvent yield, the unutilized sugars were subjected to batch fermentation., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Clostridium beijerinckii DSM 6423 was studied using different continuous production methods to give maximum and stable production of isopropanol and n-butanol. In a single-stage continuous culture, when wood pulp was added as a cell holding material, we could increase the solvent productivity from 0.47 to 5.52 g L⁻¹ h⁻¹ with the yield of 54% from glucose. The overall solvent concentration of 7.51 g L⁻¹ (39.4% isopropanol and 60.6% n-butanol) with the maximum solvent productivity of 0.84 g L⁻¹ h⁻¹ was obtained with two-stage continuous culture. We were able to run the process for more than 48 overall retention times without losing the ability to produce solvents.