SBIR Phase I: High-Power and High-Energy-Density Enzymatic Fuel Cell through an In Vitro Synthetic Enzymatic Pathway

This Small Business Innovation Research Phase I project will develop high-power and high-energy-density enzymatic fuel cells (EFCs) that can completely oxidize low-cost maltodextrin (i.e., a partially hydrolyzed starch fragment). EFCs have received increasing interest as a next-generation, environmentally friendly (micro-)power source. Compared to microbial fuel cells, EFCs have much higher power densities suitable for more applications. However, current EFCs are limited by the partial oxidization of hexose molecules by one or two redox enzymes (i.e., 2-4 mol of electrons produced per mol of glucose) and a short enzyme lifetime. The goal of this project is to demonstrate the technical feasibility of the complete oxidation of maltodextrin in EFCs through a patent-pending synthetic enzymatic pathway. The technological innovation of this project is the construction of an ATP-free and CoA-free pathway by an assembly of thermostable enzymes to generate 24 electrons per glucose unit and increase power density. As a result, EFCs are expected to feature high energy density due to the complete oxidization of the fuel, high-power density due to substrate channeling among cascade enzymes and the mitigation of product inhibition of the enzymes, and a long lifetime due to the use of thermostable enzymes. The broader impact/commercial potential of this project is developing bio-inspired sugar biobatteries featuring four appealing advantages: (i) biodegradability, (ii) safety, (iii) high energy storage density (e.g., 400 Wh electricity/kg for a 20% (w/v) maltodextrin solution, nearly three times that of lithium ion batteries), and (iv) fast refilling by adding a sugar solution. EFCs would have broad potential applications, such as rechargeable battery chargers (e.g., cellular phone chargers for outdoor uses or portable military devices), educational toy kits, and disposable (primary) batteries. In the future, miniaturized sugar-powered EFCs could potentially replace some secondary (rechargeable) batteries. Sugar-powered EFCs would be nearly 100% biodegradable, with the exception of the electrodes and wires, and are based on non-toxic and earth-abundant elements. The maltodextrin solution is neither toxic nor flammable. The innovation of EFCs equipped with this in vitro synthetic pathway would greatly promote the concept of in vitro synthetic biology and demonstrate another advantage a faster reaction rate than that of microbes due primarily to the absence of a cellular membrane. In addition, the generation of electricity from renewable and low-cost sugars, namely maltodextrin or future cellulosic materials, would decrease greenhouse gas emissions, increase national energy security, and promote rural economies.