Hi.
I found glucose concentration used for biofuel cell testing varies from ~ 5 mM to 200 mM, with a case of 27 mM, a uncommon value. Should it be around blood glucose concentration (less than 10 mM)?
So my doubt is how to make a decision on testing glucose concentration. Is it where the anodic current saturated?
Thanks!
It would make sense to measure the saturation point, as even with an enzyme of fixed Km the cell construction will vary the response characteristics widely. If you just want to measure at a single point maybe it depends on your application of interest for the biofuel cell. If it needs to run off blood, then 5mM is a normal value before a meal and you can double that after. 27mM may be a high extreme, though I believe someone has survived a recorded 144mM! If you want your fuel cel to run off soft drinks, then 280mM is a fairly typical glucose concentration (5g/dl).
I think that Marcus has offered a good answer. In general, the issue depends on: 1) what purpose is your biofuel cells (i.e., where are you going to use themt)? 2) the immobilization methods of enzymes, the Km values very sensitively rely on the enzyme immobilization modes and support materials. You could adjust Km values through using various nanomaterials and covalent or non-covalent immobilization management.
Marcus and Chi, Thanks for your kind answers.
Regarding to your answer, Chi, another question arises for me. Does Km make sense for immobilized enzymes? Generally, the Km for immobilized one is lower than free enzyme. And in my case, sometimes the Km obtained on nanoporous gold is larger than planar one. Are there some publications describing immobilized Km comprehensively?
http://www.electrochemsci.org/papers/vol8/80709242.pdf
Int. J. Electrochem. Sci., 8 (2013) 9242 - 9255
Biofuel Cells Composed by Using Glucose Oxidase on Chitosan Coated Carbon Fiber Cloth
The glucose concentration of a biofuel cell should be an appropriate concentration for the application of the biofuel cell. If implantable, 5-10mM, but if considering portable power biobattery application, then as close to concentrated glucose as possible, although 100mM is a common test case. If you are making a sealed glucose bio-battery, then concentrated fuel is needed to have high energy density of the biobattery.
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