Team:Macquarie Australia/Project/Background

Does money make the world go round? For engineers, it's energy.

The ability to effectively generate, store and conveniently access energy is the hallmark of the developed world. These systems are integral to our everyday lives including: transport, heating, industrial production, control of water supply and recreation.

The requirement for alternative energy sources

Fossil fuels have been the staple of energy needs throughout the 20th century. Their consumption far exceeds the rate which they can be formed and this has led theorists to predict the catastrophic economic consequences of exhausting the non-recyclable resource, culminating in theories such as the famous 'peak oil' proposition [1]. While advances in technology for gas and oil exploration and extraction have resolved the scarcity of energy resources in the short-term[2]. Furthermore our capacity to withstand the release of carbon by-products remains a pertinent challenge to our generation.

Alternate green sources harvest their energy from naturally replenished, or renewable, sources. Methods of harvesting can be direct or indirect including converting photons to electricity in solar cells or harnessing the power of the wind or the waves. These are characteristically producing few harmful byproducts. One of humanity's first energy sources was also renewable: the usage of biofuels, organisms that harvested solar energy and stored them as energetic organic compounds. These were burnt, and in the present time, fermented, allowing a useful conversion of solar energy to that useful for human purposes.

Solar Energy Redux: Obtaining Usable Energy

Despite the higher efficiency of direct photovoltaic conversion of photons to electrical energy, biofuels remain a relevant option. Concerns have been raised regarding the industrial processes and hazardous materials involved in the creation of photovoltaic systems, often requiring significant fossil fuel energy to produce [3] [4]. Biofuels are cheaper, requiring less capital and energy to produce. They are self-replicating and require uncomplicated maintenance. The drawbacks are in efficiency: high efficiency biofuels produce fuels capturing a peak of 6% of solar energy, whereas the thermodynamic limit of photovoltaics is around 14%[5].

The salient difference is how the energy is used; biofuels provide an efficient mechanism for storing energy, sealing it within energetic organic compounds such as ethanol or hydrogen gas, enabling relatively easy transportation and storage of energy in comparison to batteries, that are often heavy and lose energy over time. The place for biofuels in the 21st century is producing a convenient storage mechanism for energy, particularly for vehicles, where there is a need to carry fuel for long distances without opportunity to refuel on electrical power. Biofuel research and development in the 21st century has focused around high efficiency bioethanol production for these purposes[6].

Our Response

The Macquarie iGEM team aims to give synthetic biologists the tools for a bacterial powerhouse that can harvest solar energy. By developing an enzyme pathway capable of synthesising the primary component of photosystem-II, namely chlorophyll-a, the first step toward an entirely synthetic photosynthetic pathway is taken. These parts will also be expressed in a foreign but well characterised host, namely, E. coli K 12 strain.

It is hoped that by successfully engineering and demonstrating the capacity for this organism to express the relevant enzymes, and produce chlorophyll-a, that the ATP and NADPH produced by the photosystem can be used to produce biofuel substrates. Successfully coupling the photosystems products to known proteins for the production of substrates is one such future use, with proteins available to manufacture hydrogen [7], which may be transfected into an expression host to create an entire synthetic system for the production of hydrogen gas.

References

• Hsu, J. Oil Production to Peak in 2014, Scientists Predict.
• Technology, J.R., Energy Innovation: Policy and We Will Not Run Out of Fossil Fuels (Op-Ed).
• Mohr, N., Meijer, A., Huijbregts, M.A.J., and Reijnders, L. (2009). Environmental impact of thin-film GaInP/GaAs and multicrystalline silicon solar modules produced with solar electricity. Int. J. Life Cycle Assess. 14, 225–235.
• Fthenakis, V.M., Kim, H.C., and Alsema, E. (2008). Emissions from Photovoltaic Life Cycles. Environ. Sci. Technol. 42, 2168–2174.
• Sydney, D.T.S.L. in A. at U. of For efficient energy, do you want solar panels or biofuels
• Liew, W.H., Hassim, M.H., and Ng, D.K.S. (2014). Review of evolution, technology and sustainability assessments of biofuel production. J. Clean. Prod. 71, 11–29.
• Australian National University, Water and sunlight the formula for sustainable fuel - Newsroom – ANU.