Advancing Biotechnologies for Fuel Generation: Exploiting Transmembrane Cytochromes for Solar Energy Conversion

有关化石燃料储量减少和对燃料安全的担忧的报道经常成为新闻头条。不断上涨的燃料成本每天都在提醒人们，能源需求不断增长的全球社会所面临的挑战。在这方面，也许令人惊讶的是，我们可以利用的许多可再生能源，即阳光、风能和海浪，仍然基本上是未开发的资源。这主要是因为当我们想玩电脑游戏、开车等时，将这些能源形式转化为燃料存在着挑战，这些燃料可以根据需要释放能量。然而，在植物光合作用过程中，燃料是由阳光中的能量自然产生的。绿色叶绿素色素对光的吸收产生了一个带电的电子，该电子沿着金属中心链被引导到制造糖的催化剂上。当我们和所有动物的能量在消化后释放时，这些糖为我们和所有动物提供燃料。然而，使用种植的植物生产生物燃料是有争议的，因为农业也是养活世界的必需品。因此，受自然过程的启发，我们建议建立一个人工光合作用系统。从本质上说，我们希望在微生物身上放置微型太阳能电池板，以便利用阳光来驱动氢气的生产--氢气是一种按需释放能量的先进技术。我们将使用染料和半导体粒子作为机械和化学上坚固的材料，以捕捉阳光中的能量并产生带电的电子。我们将把这些粒子连接到生物版本的导线上。这些电线是由跨越膜的血红素蛋白制成的，这些膜为大自然提供了将充满水的房间(即细菌内部)隔开的解决方案。血红素线是由‘呼吸岩石’的微生物自然产生的，在这些线将被激发的电子传递到膜上后，它们将驱动酶催化产生氢。我们新型的仿生光催化剂将建立新的原理，用于设计具有空间分离的燃料释放位置的均相光催化剂，并提供维持这一过程所需的电子。我们设想，我们的光催化剂将具有多功能性，只要稍加修改，它们将能够利用太阳能制造药物和精细化学品。

Reports concerning dwindling reserves of fossil fuels and concerns over fuel security are frequent news headlines. The rising costs of fuel are a daily reminder of the challenges faced by a global society with ever increasing energy demands. In this context it is perhaps surprising that so many of the renewable energy supplies available to us, namely, sunlight, winds and waves, remain largely untapped resources. This is mainly due to the challenges that exist in converting these energy forms into fuels from which energy can be released 'on demand' when we wish to play computer games, drive a car and so on. However, during plant photosynthesis fuels are made naturally from the energy in sunlight. Light absorption by the green chlorophyll pigments generates an energised electron that is directed, along chains of metal centres, to catalysts that make sugars. These sugars fuel us, and all animals, when their energy is released following digestion of a meal. However, using farmed plants to produce biofuels is controversial as agriculture is also required to feed the world. As a consequence, and inspired by natural processes, we propose to build a system for artificial photosynthesis. In essence, we wish to place tiny solar-panels on microbes in order to harness sunlight to drive the production of hydrogen - a fuel from which the technologies to release energy on demand are well-advanced. We will use dyes and semi-conductor particles as mechanically and chemically robust materials to capture the energy in sunlight and generate energised electrons. We will couple these particles to biology's version of conducting wires. These wires are made from heme proteins that span membranes that provide Nature's solution to compartmentalising water-filled chambers (i.e., the inside of the bacterium). The heme-wires are produced naturally by 'rock-breathing' microorganisms and after these wires have transferred the energised electrons across the membrane they will drive enzyme catalysis to produce hydrogen Our novel bio-mimetic photocatalysts will establish new principles for the design of homogeneous photocatalysts with spatially segregated sites for fuel-evolution and the supply of electrons that is needed to sustain this process. We imagine that our photocatalysts will proove versatile and that with slight modification they will be able to harness solar energy for the manufacture of drugs and fine chemicals.