Question: Green chemistry is an area of biochemistry I particularly enjoy due to the interdependence of engineering, chemistry, and biology and how they can be employed to solve real world problems of sustainability. One green chemistry concept that fascinates me is artificial photosynthesis. What is artificial photosynthesis and what are the implications of researching and developing this technology?
Answer: Chong Liu and a group of biochemists and material scientists at University of California Berkeley have developed artificial photosynthetic technology. This comes in the form of nanowire array-bacterial complexes which harvest light energy, atmospheric carbon dioxide, and water to fix the gas into usable compounds like acetate (Liu et al, 2015). Nanowire arrays are comprised of silicon and titanium oxide which generate excited electrons when light energy is absorbed, similar in function to pigments and photosystem complexes in photosynthetic organisms. Living within the nanowire “forest” are anaerobic bacteria, Sporomusa ovata, which use the excited electrons on the surface of the wires to efficiently reduce carbon dioxide gas into acetic acid. Acetate, the deprotonated form, is a biochemical intermediate which can enter into many metabolic pathways and act as a precursor to biomass like glucose, an energy-rich carbohydrate.
This technology represents a potential solution to the growing problem of atmospheric carbon dioxide gas which plays a role in the greenhouse effect and global climate change due to fossil fuel combustion. Developing nanowire-bacterial hybrid photosynthesis machines could both create usable organic compounds like acetate which can be used to synthesize drugs for research and medicine and remove atmospheric carbon to stabilize rising levels of the gas. Presently, the team achieves 0.38% efficiency, and plans to improve on design to achieve 2% and eventually 10% efficiency, at which point the technology could be employed commercially.
- Joel S.
Liu, C., Gallagher, J. J., Sakimoto, K. K., Nichols, E. M., Chang, C. J., Chang, M. C. Y., and Yang, P. (2015) Nanowire–Bacteria Hybrids for Unassisted Solar Carbon Dioxide Fixation to Value-Added Chemicals. Nano Letters. 15, 3634–3639