Effects of temperature on alcohol tolerance of microbes
By Neil Stacey
It has been established that dissolution of membrane lipids plays a role in the toxicity of ethanol and butanol to micro-organisms; a matter of particular importance for the production of bio-alcohol fuels using fermentation by microbial activity. However, solubility is a phenomenon heavily governed by temperature.
It follows that microbial tolerance of these substances will tend to vary with temperature, a phenomenon that has not been studied outside of a narrow range of temperatures in which fermentation is typically conducted, largely because fermentation rate is optimized within that range. However, the main costs involved in bio-alcohol production are feedstock material followed by separation costs. The former of these cost factors is determined by fermentation yield relative to mass and the latter is determined by alcohol product purity which is in turn governed by alcohol tolerance. Fermentation rate only affects reactor sizing, a moderate factor in capital cost with little bearing on operating cost. Hence, compromising fermentation rate in pursuit of alcohol tolerance by exploring unconventional temperature ranges could potentially offer improvements in overall economic performance of bio-alcohol production.