The recent breakthrough achieved in a steadily expanding field of the enzyme biofuel cell development1 and the predicted exhaustion of the earth Li and Pt resources actually change the public attitude to the future role of the biofuel cells. They appeared to be highly attractive alternative for a number of special applications, such as disposable implantable power suppliers for medical sensor-transmitters and drug delivery/activator systems and self-powered enzyme-based biosensors; and they do offer practical advantages of using abundant organic raw materials for clean and sustainable energy production. Progress in enzyme biotechnology and electrochemistry enables now construction of biofuel cells exploiting a wide spectrum of enzymes wired to electrodes, able of prolonged for up to several months function.1-3 One of the most attractive designs exploits direct electronic communication between the biocatalysts and electrodes,3 a good example is a simple in preparation and practically useful 1.7 V biobattery based on the traditional battery-type Zn anode and a bi-enzyme biocathode operating for 82 h using glucose/O2 couple as an oxidizer (3 days of continuous operation are recommended for continuous in vivo glucose monitoring in diabetes patients). However, the most attractive are oxygen-reducing enzymes such as blue-copper-containing laccases coupled to electrodes, which provide the 4e- bioelectroreduction of O2 to H2O (1.23 V vs. NHE) at potentials approaching the thermodynamic ones. Exploitation of laccase-based biocathodes in the biofuel cells and in the hybrid biobattery-type or photovoltaic power sources could essentially broaden their application, enabling extraction of energy from the sea water/water dissolved oxygen. Here we demonstrate up to 0.8 mW cm-2 extracted power densities and 1.5 month operation of domestic devices exploiting cheap and simple hybrid bio-batteries based on fungal laccases covalently attached to carbon materials. The main technological drawback of such systems is that the activity of fungal laccases is restricted to acidic media, which makes them inappropriate for operation in physiological fluids or sea water, having basic/neutral pH. We have studied several bacterial laccases that might enable biocathode operation in basic media, and for which hitherto their wiring to electrodes was not successful. We demonstrate that the absence of bioelectrocatalysis was connected with the orientation of laccases at electrodes inappropriate for efficient electron transfer between the electrode and enzyme.5 To achieve the proper orientation of laccases at electrodes we used carbon nanomaterials coupled to bio-mimicking promoters, and that allowed to get efficient electronic coupling between laccases and electrodes, which resulted in highly efficient bioelectrocatalysis of O2 reduction. The hybrid biobattery exploiting the bacterial laccase biocathode is shown to efficiently operate in basic media.
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1st International Conference on Bioinspired Materials for Solar Energy Utilization, 2011