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Figure 1: Cancer incidence in Kentucky, all sites of cancer, all races, ages and genders, 2010-2014. High incidence counties are concentrated in Appalachia where low socioeconomic status coincides with environmentally destructive mining practices. Generate this map and others like it.
 

Figure 2: Microbial and enzymatic electrodes in a fuel cell, from Higgins et al (2011) ACS Catal. 1(9) 994-997. Link to the paper.
 

Figure 3: Risk posed by agricultural insecticides in runoff. From the Helmholtz Centre for Environmental Research - UFZ (2015) Link to the Press release of 25 Feb. 2015.
 

Figure 4: Lignin Valorization. Enzymes (coloured circles) are depicted catalyzing the depolymerization of lignin fragments, and other enzymes are then used to modify lignin monomers converting them to fuel or value-added compounds. Immobilization of the enzymes in pores of a membrane (grey) permits efficient real-time adjustment of duration of contact between enzymes and lignin stream via the flow rate through the membrane, and the polymer matrix (black waves) entrapping the enzymes extents their active lifetimes. Lignin structure is from Anderson et al (2016) ACS Sus. Chem. Eng. 4 6940-6950. Link to the paper.

0. Motivation.

There is no planet B.

We must adopt ways to live lighter on our precious earth. Fortunately many new technologies are available to help us consume less energy and water while also living higher-quality lives. However implementation remains a challenge. The Miller lab seeks to make solutions from nature practical for industrial and domestic use. Out twin foci are energy and water. In both cases, we turn to enzymes. We are learning about energy conservation at the level of electrons from enzymes that employ a recently-appreciated mechanism to enable organisms to flourish in meager environments. We are also putting enzymes to work, cleaning up used water so that it can be used again, and again, and again....

1. Energy.

Life has been here before. Organisms present today retain a heritage of enzymes that evolved under severe selection for energy efficiency when organisms were anaerobic and unable to tap the huge energy bonanza made possible by the combination of oxygenic photosynthesis and respiration. These enzymes employ a newly appreciated mechanism of energy conserving electron transfer called electron bifurcation (or confurcation in reverse). We are working to elucidate the molecular mechanisms of electron bifurcation, so that these principles can be incorporated in the design of new materials and devices to confer upon them the enviable energy efficiency of anaerobes.
             Confurcation allows enzymes to combine the energies of electrons with different reducing potentials in such a way that the minimum sufficient energy is used to execute needed chemistry. Using the analogy of currency, one saves 15 ¢ by paying 35 ¢ using a quarter and a dime, as opposed to two quarters. Confurcating enzymes are able to draw electrons from two different sources equivalent to accepting coins of two different values.
            Bifurcation allows enzymes to accept a pair of electrons of the same reducing power and reallocate energy among them to yield a stepped-up electron with much higher reducing power (more negative reduction potential). This super-reducing electron can make chemical reactions possible that would otherwise not be accessible to the organism. The cost is that the left-over electron is releases with very little reducing power. However the benefit is greater, as essential resources such as fixed nitrogen are limiting in many environments. The organisms able to fix their own nitrogen from atmospheric N2 gained access to an inexaustible resource that was inaccessible to their competitors. We seek to make such game-changing versatility possible for man-made devices by elucidating the mechanism and principles that can be implemented in synthetic systems.

2. Water.

Water is our other focus. The problem is different in that most of our uses do not actually consume water, but return it to the environment in a condition that prevents it re-use. We are advancing technologies that will be easy to implement in modular, versatile devices that can be deployed at the sources before contaminated water enters the watershed and the volumes become large, or at the point of use where only the water that is to be drunk need be brought to potable standards. Here we exploit the fact that enzymes are non-toxic, native to water and able to retrieve contaminants present at very low concentrations. Thus the implementation of enzymes instead of incineration saves energy costs of drying, eliminates need for concentration or separation and can focus the treatment on the specific compounds that pose the problems.
            Agricultural runoff carries herbicides, pesticides and veterinary antibiotics into the waterways spread over large rural areas. Thus large volumes of water are affected over a vast area. We envision portable modules that act as a short stretch of culvert or drain pipe, but are filled with membranes and filters decorated with appropriate enzymes. These would be placed at the site of generation such as outflows of drainage ditches that run alonside fields and drains of CAFO facilities. As the water passes through the filters, the resident enzymes would transform their toxin targets. There would be no need for containment. To permit such devices to be maintenance-free we are working with chemical engineers to optimize membrane supports and immobilization methods that minimize clogging, fouling and enzyme inactivation in use. Moreover because our enzymes are redox enzymes, we are developing ways to monitor performance and effluent water quality via electrochemical currents such as those we measure for eletrode-immobilized enzymes.
            The waste streams of cellulose extraction contain vast amounts of lignin, making it an exciting underexploited resource. We are using enzyme functionalized membranes to convert lignin fragments into valuable food additives. Such an approachs confers value on the waste stream, incentivizing its conservation and diminishing the new resources needed by maximizing the utilization of what we already have. While such projects would have been fantasy 10 years ago, enzymes are now active ingredients of laundry detergents and industrial formulations. Enzymes can provide many of the benefits of microbes but without the biohazards. Legislating reduction and decontamination of waste is laborious, however if waste becomes a source of energy and value-added products that are convenient and economical to access, then we will have transaformed the issue from waste to opportunity.

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Updated: Oct. 2017                                                                                               

Copyright 2017 A.-F. Miller     

Comments: A.-F. Miller