Soil Remediation With Plant-Fungal Combinations

There is a significant need for an inexpensive biological approach to recover specific, targeted metals and other target materials in e-waste or other aqueous solutions that requires minimal input of resources, including energy. This invention is a method of removing or adsorbing a target substance or material, for example, a metal, non-metal toxin, dye, or small molecule drug, from solution, by functionalizing a substrate with a peptide configured to selectively bind to the target substance or material and to bind to the substrate. The substrate is fungal mycelium, and the naturally-occurring or bioengineered peptide is called a target-binding domain, which is chemically bonded to a selected solid substrate. The target chemical species binds to the target-binding domain and is removed from solution. The target can be any chemical species dissolved or suspended in the solution. Capture of the target by the substrate can isolate and allow removal of the target substance from solution, or for utilization in water filtration, or recovery of targeted chemical species from solution, particularly aqueous solution applications. The peptides used include (i) fusion peptides and/or proteins containing metal-binding domain sequence and optionally containing substrate-binding domain sequence; (ii) fusion peptides/proteins containing a metal-binding domain and a chitin-binding domain; and (iii) nucleic acids encoding fusion peptides and/or proteins containing metal-binding domain sequence. The technology enables simple scale up to a level that could be successfully implemented in an environment with limited resources, such as on a space mission or on earth in developing countries with poor access to clean water.

Because resupply of commodities for long duration space missions would be prohibitively expensive and could take an extensive length of time to reach habitats in orbit around or on other planetary bodies, it is critical that astronauts have the ability to recycle and reuse local waste streams to provide resources such as clean water, fuel, and nutrients for growing plants. Scientists at Kennedy Space Center and the University of South Florida have developed a technology that addresses this critical mission need. The modular system design incorporates all wastewater streams and some food waste including urine water, hygiene water, humidity condensate, Sabatier water, fecal waste, laundry water, and organic food waste. These sources are fed simultaneously into the system, and a function-driven, sequential purification process occurs. The primary processes include carbon conversion, phase separation (solid/liquid/gas), disinfection, nutrient/salts management, and salts balancing to generate a clean water stream. The heart of the closed-loop bio-regenerative system is an anaerobic membrane bioreactor (AnMBR), which takes raw wastewater streams and utilizes an anaerobic microbial consortium to carry out the breakdown of the organic matter. An ultrafiltration membrane captures and destroys pathogenic bacteria and viruses. The AnMBR system generates a clean water stream containing fertilizer constituents which can be used to cultivate either microalgae (for food, pharma/nutraceuticals, fuel or bioplastics) in photobioreactors or crops in hydroponic systems. The system also generates methane and hydrogen gas which can be used for fuel (or conversion to bioplastics), and CO2 which can be used to support plant growth.

The Surface-Adhering BioReactor (SABR) is a novel microbial cell cultivation platform that mimics the way vascular plants use transpiration to deliver nutrients to their cells. In this biomimetic platform, microbial cells are cultivated as immobilized cells on a porous substrate where transpiration is used to passively deliver water and nutrients as well as harvest and concentrate secreted biomolecules by the microbial cells. The SABR transports nutrients to microorganisms without using a pump. Instead, evaporation and the cohesive property of water are exploited to pull the nutrient medium through the device, with a high degree of control, on an as needed basis. It eliminates the hydrodynamic shear stress on the cells and decreases the working volume of water needed for cultivation by a factor of 25 compared to planktonic bioreactors. Furthermore, the transpiration mechanism allows for the concentration of secreted products in areas of relatively fast evaporation, thus providing a passive means of secreted product harvesting. By matching the time scales of nutrient medium delivery and product harvesting with the time scales of growth and product formation, minimal energy is wasted in bioreactor operation. Transpiration enables a passive cooling system for the cells where either externally imposed or internally generated heat due to cellular activity is mitigated, thus preventing overheating that can lead to decreased productivity or even cell death. This technology enables significant reductions in energy input for cultivating microorganisms.

Early exploratory research with the plasma treatment of water and inedible biomass revealed problems with both efforts. Plasma treatment of water lowered the pH of the water below acceptable levels for plants. Additionally, inedible biomass treated with plasma for nutrient recovery has to be dissolved in acid to enhance that nutrient recovery, and acid can be difficult and dangerous to handle. The technology described here utilizes a single plasma torch to treat both water and inedible biomass. Plasma treatment of the water creates useful species, such as nitrates, to the water which are beneficial for plant growth. However, plasma treatment of water also forms nitric acid, causing the water to be too acidic for plants. Plasma treatment of inedible biomass breaks down the cellulose inside the plant material and reduces it to ash, liberating nutrients such as potassium, calcium, sodium, and phosphorus. Researchers determined that careful dosage of the appropriate amount of the recycled ash to the plasma treated water balances the water's pH level and also adds nutrients that can further enhance plant growth. This method eliminates the need for acid treatment of the plasma treated biomass. For cleaning applications, water can be treated with plasma to either high or low pH extremes for shock sanitation treatment. The system requires a high voltage power supply and a plasma torch. The torch requires a tube for gas transportation, an electrode inside the tube, and an electrode outside the tube. Air can be used for both treatments. The plasma system can be optimized to condense the system into a lunchbox sized package to generate the treated water and ash.

The photobioreactors allow light to enter through their transparent upper surface and optimizes the efficiency of light utilization with a light-reflective lower surface inside. Deployed in the marine environment, the gradient between the freshwater inside the system and the saltwater outside drives forward osmosis. The water removed through semi-permeable (forward osmosis) membranes is cleaned as it is released into the marine environment. In addition, this process concentrates nutrients in the algae medium to stimulate growth, and concentrates the algae to facilitate harvesting. The harvested algae can be used to make biofuels, fertilizer, animal food, or other products. The photobioreactors are intended for use in naturally or artificially protected marine environments with small waves and gentle currents. The system can also be used in artificial brine pools and freshwater basins or reservoirs, however in freshwater the forward osmosis feature cannot be used.