Chapter 29 : Applications of Stress Response Studies: Biofuel Production

Abstract:

This chapter gives examples of unintentional or unwanted chemical and physical stresses and nutrient or physical stresses, and describes general strategies that are used to manage or to sidestep them. This is followed by a discussion of metabolic imbalances as a universal stress associated with microbial biofuel production. Although, currently, the amount of H2 produced by these systems is relatively small and insufficient to consider scaling up, it is a starting point that can likely be improved on. Strategies that have targeted photosystem II activity have yielded mutants that produce H2 in the presence of sulfur and have favorable H2 production rates compared to the parent strain. This illustrates that it is possible to capitalize on detailed knowledge of a stress response to design strategies for enhanced biofuel production. Most fermentative microbes, particularly those that produce longer chain length alcohols such as butanol, produce a mixture of reduced and more oxidized organic fermentation products as a strategy to capture additional ATP by substrate level phosphorylation. Diversion or enhancement of one particular set of reactions toward excreting an energy rich, highly reduced compound can lead to either an excess or insufficiency of key intermediary metabolites. Such metabolic imbalances are another form of cellular stress that can compromise growth.