Cyanobacterial Biofuel Production: Current Development, Challenges and Future Needs

As the need to replace fossil fuels increases and global energy needs expand the drive to find alternative, sustainable sources of fuels have accelerated. Microbial sources are attractive because of the rapid growth rates of microorganisms and their potential techno-economic advantages. Cyanobacteria are prokaryotic photoautotrophs (utilise photosynthesis and CO2 for energy and carbon needs), which have emerged as potentially ideal candidates as sources of sustainable biofuel producers once metabolically engineered to do so. Over the past decade, there has been much interest in utilising cyanobacterial model species as proof of concept to produce and overexpress a range of biofuel candidates ranging from ethanol, butanol and other compounds ranging from hydrogen to fatty acids. Research on model biofuel candidates has revealed the potential for biofuel production but also revealed a number of challenges to future development. These challenges range from (1) biological, concerning the genetic constructs, their expression, stability and tolerance to the recombinant biofuel product, (2) production efficiency and biofuel recovery strategies and (3) economic, concerning the viability of production at a scale relative to the market price of the biofuel. Here, various technical challenges will be addressed based on experience and insights gained from the production of ethanol in model cyanobacteria, where many of these challenges are identified and strategies for future development discussed based on the current state of the art.