Practical Aspects of Butanol Production

Abstract

This chapter discusses practical approaches for biobutanol production, including strategies for reducing or eliminating butanol toxicity to the culture, as well as exploiting both physiological and nutritional aspects of the fermenting microorganisms in order to achieve better product specificity and yield. Recent developments in liquid biofuel technology, the uncertainty of petroleum supplies, the finite nature of fossil fuels, and environmental concerns have revived research efforts aimed at obtaining butanol from renewable resources. Solventogenic clostridia and many other anaerobes transport sugars into cell membranes through a phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS), and this PTS is involved in the transfer of a phosphate group from PEP to the substrate sugar. Generally, process controls during fermentations may be classified as physical (agitation speed, temperature, pressure, and aeration rate), chemical (pH, redox potential, dissolved oxygen, and dissolved CO2), and biological (biomass concentration, oxygen uptake, and production rates of H2, CO2, CH4, etc.) variables. The solventogenic clostridia have the ability to reassimilate the fermentation intermediates (acids) for solvent or butanol production and stabilize the pH in the process. pH measurement during butanol fermentation is important in order to accurately monitor the fermentation progress and in extreme cases prevent acid crash. Accurate online pH monitoring is important for early detection of poorly buffered pH media.