Sugar is an excellent energy source. As a culture we’ve probably known about it since before we were Homo sapiens. The problem is, unless you’re a living organism or some kind of incendiary device, extracting that energy is difficult. In nature, an enzymatic pathway is used — a production line of tailor-made enzymes that meddle with the glucose molecules until they become ATP. Because it’s easy enough to produce enzymes in large quantities, researchers have tried to create fuel cells that use artificial “metabolism” to break down glucose into electricity (biobatteries), but it has historically proven very hard to find the right pathway for maximum efficiency and to keep the enzymes in the right place over a long period of time.
Sugar-powered biobattery can achieve an energy-storage density of about 596 ampere-hours per kilogram (A-h/kg) — an order of magnitude higher than the 42 A-h/kg energy density of a typical lithium-ion battery. A sugar biobattery with such a high energy density could last at least ten times longer than existing lithium-ion batteries of the same weight.
This nature-inspired biobattery is a type of enzymatic fuel cell (EFC) — an electrobiochemical device that converts chemical energy from fuels such as starch and glycogen into electricity. While EFCs operate under the same general principles as traditional fuel cells, they use enzymes instead of noble-metal catalysts to oxidize their fuel. Enzymes allow for the use of more-complex fuels (such as glucose), and these more-complex fuels are what give EFCs their superior energy density.
For example, the complex sugar hexose — upon complete oxidation — can release 24 electrons per glucose molecule during oxidation, whereas hydrogen (a fuel used in traditional fuel cells) releases only two electrons. Until now, however, EFCs have been limited to releasing just two to four electrons per glucose molecule.
Team developing this battery constructed a synthetic catabolic pathway (a series of metabolic reactions that break down complex organic molecules) containing 13 enzymes to completely oxidize the glucose units of maltodextrin, yielding nearly 24 electrons per glucose molecule.
Team put specific thermostable enzymes into one vessel to constitute a synthetic enzymatic pathway that can perform a cascade of biological reactions to completely “burn” the sugar, converting it into carbon dioxide, water and electricity.
Unlike natural catabolic pathways for the oxidation of glucose in cells, the designed synthetic pathway does not require costly and unstable cofactors, such as adenosine triphosphate (ATP, critical for energy processes in human cells), coenzyme A, or a cellular membrane.
Team used two redox enzymes that generate reduced nicotinamide adenine dinucleotide (NADH) from sugar metabolites. NADH, a reducing agent involved in redox reactions, is a natural electron mediator that carries electrons from one molecule to another.
This new synthetic pathway enables the biobattery to extract the entire theoretical number of electrons per glucose unit and thereby use all the chemical energy in the sugar. This is a significant breakthrough.
In addition to its superior energy density, the sugar biobattery is also less costly than the lithium-ion battery, refillable, environmentally friendly, and nonflammable.
Credit to :chief researcher, Y.H. Percival Zhang