Biohybrids for Solar Chemicals and Fuels: Whole-cell Photocatalysis by Non-photosynthetic Organisms.

点击翻译按钮获取中文摘要

From news headlines to social media streams, we are constantly reminded of the need to help secure a healthy planet for future generations. The abundance of solar panels in urban and rural landscapes immediately illustrates how, nationally and as individuals, we are embracing technology to do this. Solar panels absorb sunlight and convert its energy to electricity. This helps to mitigate against climate change by lowering our use of fossil carbon reserves and harnessing sunlight is very sensible; in just two hours the sun provides Earth with sufficient energy to meet its present annual energy demand. However, solar panels are not without problems since they are constructed with toxic materials and suffer from intermittent output, which may not match patterns of energy demand. Developing more sustainable routes to harness the energy of sunlight is a global challenge. To help meet this challenge, and inspired by photosynthesis in green plants, we aim to combine the best of natural and synthetic approaches to solar energy conversion for the sustainable production of chemicals including fuels.Photosynthesis is Nature's way of harnessing solar energy. Using abundant and non-toxic elements assembled as environmentally benign proteins, green plants absorb sunlight to drive the synthesis of fats and sugars. Amazingly, the only side-product of this reaction is the oxygen we need to breath. Fats and sugars provide fuels that we, like plants, can use for energy whether it is day or night, sunny or cloudy. Natural photosynthesis is a self-sustaining, renewable model for solar energy conversion but it is not without bottlenecks. The light-harvesting systems absorb only a small fraction of the solar spectrum and are easily damaged - during the day they are usually replaced every 30 minutes. By contrast, synthetic light-harvesting materials like those in solar panels, are more robust than natural photosystems. In addition 'rainbow absorbers' can harness much more of the solar spectrum. Our research will combine robust, synthetic light-harvesting materials with non-photosynthetic bacteria in a powerful, sustainable solution to delivering complex chemical transformations. We aim to develop systems producing fuels, for example, ethanol (from a major underutilised by-product of biodiesel production), hydrogen (from water) and formate (from carbon dioxide a greenhouse gas). Importantly our biohybrids will simultaneously produce two different fuels but no side products so they are true mimics of natural photosynthesis in their chemical efficiency. How will we do this? We will use detailed knowledge of the structure of a protein conducting electrons from the inside to the outside of Shewanella bacteria. This knowledge allows us to engineer the external surface of the Shewanella bacteria for selective labelling with light-harvesting electrocatalysts. Then, powered by the energy of sunlight, electrons will move between enzyme catalysts inside the bacteria and the synthetic catalyst outside the bacteria in order to couple the production of one fuel inside the bacterium and a different fuel outside the bacterium. Our approach allows us to use enzymes to deliver complex transformations without expensive purification that can result in fragile systems. By using bacteria there is also the possibility that the performance of our systems will benefit from natural processes of enzyme self-repair and regeneration.