Patent Application
20080090736
NONE
1. “2002 Review by the State Water Resources Control Board (SWRCB) of California” 2002. (http://www.swrcb.ca.gov/ab885/technosite.html)
2. Logan, B. E., Regan, J. M. Electricity-producing bacterial communities in microbial fuel cells. Trends Microbiol. 2006 December; 14(12):512-8. Review.
3. Lovley, D. R. Microbial fuel cells: novel microbial physiologies and engineering approaches. Curr Opin Biotechnol. 2006 June; 17(3):327-32. Review.
4. Oh, S. E., Logan, B. E. Hydrogen and electricity production from a food processing wastewater using fermentation and microbial fuel cell technologies. Water Res. 2005 November; 39(19):4673-82.
This invention relates generally to metabolic reaction networks, and more specifically to finding and customizing efficient microorganisms to metabolize bio-wastes in wastewaters or in other forms of wastes, extract desired clean energy and at the same time to produce clean water or other useful materials
Civilizations have historically flourished around major water systems, metropolises own their success to the accessibility of water. Water is one of the most vitally necessary yet frequently overlooked resources necessary for our survival. Due to the higher prevalence of human impacts on the environment, water pollution has become an increasingly significant problem. The wastewater generated by anthropogenic influences need to be processed daily to ensure clean water consumption.
The biological treatments of wastewater (e.g. trickling bio-filter, activated sludge process, suspended growth treatment systems) are among the oldest and most well characterized technologies. Currently, industrial wastewater is typically treated by aerobic systems that remove contaminants prior to discharging the water to river, lake or undergroung. Although the aerobic system is effective at cleaning waters, a major drawback is that these treatment systems require large amounts of electricity for proper operation. Annual power usage of a single residential system is in the range of 750 to 1500 kWh. [ref 1, 2002] Aerobic systems also require continuous air supply which adds substantial maintenance cost for long term operation. The current wastewater treatment plants in U.S. used 5% of national electricity to do wastewater treatment, which is equivalent to about $10 billion dollars.
Another disadvantage of the aerobic system is the production of large amounts of sludge. In current wastewater treatment process, after aeration by the aerobic bacteria, sludge is generated in the form of wastewater residues and requires additional processing. Commonly this sludge is shipped to landfills to decompose, which raises additional environmental pollution concerns. Additionally, the aerobic process reduces the dissolved oxygen in the wastewater which is detrimental to fish and other aquatic life. Thus, there is an urgent need to develop economically feasible new technologies.
New processes such as anaerobic systems, which are characterized by the absence of free oxygen from the treatment process and typically used for the treatment of waste that has a high concentration of biodegradable organic material, are developed. The anaerobic respiration process produces hydrogen, methane, and carbon dioxide, which are further used to provide energy services, and requires much less electricity than the aerobic system. The annual power usage of a single residential system is in the range of 50 to 100 kWh (7% of aerobic system) and requires no air supply [ref 1]. Another advantage of anaerobic systems is that they do not require subsequent soil distribution system and are therefore more adaptable to sites that have restrictions for other types of treatment systems, such as areas with high groundwater. Additionally, the residual semi-solid material left from the wastewater treatment processes (sludge) produced in an anaerobic system is far less than that produced by comparable aerobic systems. Perhaps the biggest advantage of an anaerobic system is its ability to generate clean energy with minimal energy consumption during the water treatment process. By using anaerobic microorganisms and their inherent fermentation pathways, hydrogen and methane gases can be directly harvested and converted to usable energy.
However, although methane production via anaerobic digestion is a mature process that has been most commonly used within full-scale facilities so far, it has some major drawbacks as well. For examples, most wastewater is too dilute to be treated using this technology to produce methane efficiently; it cannot operate at the normal temperature and requires heat for operation; it needs gas treatment and methane collection facilities; it needs “heat to electricity generation” facilities, such as a gas turbine generator.
More recently, the microbial fuel cell (MFC) technology has emerged as a novel approach to harvest energy from dissolved biomass. MFCs are devices that generate current by using bacteria as the catalysts to oxidize organic or inorganic substances. Electrons produced by the bacteria from these substrates can be transferred to the anode (negative terminal), and then flow to the cathode (positive terminal) through a conductive material containing a resistor which links the anode and cathode. There are several ways to transfer electrons to the anode, such as by electron mediators or shuttles; by direct membrane associated electron transfer; by nanowires produced by the bacteria, etc. If no exogenous mediators are added to the system, the MFC is classified as a “mediator-less” MFC[ref 2].
One application of MFC is to convert organic matters in wastewater to electricity using electrogenic bacteria. The organic matter can be from the original wastewaters or the leftover matter such as acetate, butyrate, and lactate after 15% hydrogen is generated.
MFC possesses several advantages over anaerobic digestion such as: it can produce electricity directly from organic waste without the need for gas treatment; it can convert energy at temperatures below 20° C. and at low substrate concentration levels, where the processes can not be performed using anaerobic digestion [ref 3]. Historically, MFCs do not produce much electricity economically. In last 10 years, however, power density from MFC has rapidly increased by optimizing the MFC equipment and by choosing smart microbes. While the architecture of MFC has been improved significantly to reduce construction and operating costs, and to increase power densities over the years, the microbiology of MFC biofilms and the effects of the ecology on MFC performance have not yet been explored thoroughly. The high diversity of metabolic capabilities the microorganisms is promising to the harvesting of the remaining renewable energy.
Numerous bacteria which can respire anaerobically are capable of using macroscopic electrodes as electron acceptors. MFCs are operated using these bacteria either through pure cultures or mixed cultures. Shewanella putrefaciens, Pseudomonas aeruginosa, Geobacter sp., Rhodoferax ferrireducens are revealed to be used in pure-culture-operated MFCs from several srudies. Thermophilic bacteria, such as Bacillus licheniformis or Bacillus thermoglucosidasius are also reported to be used when MFCs are operated at high temperature. In mixed-culture-operated MFC, its performance is determined by the interaction of the whole microbial community, namely “electrochemically active consortium”. The sources of the mixed cultures are either from sediment (both marine and lake sediment) or activated sludge from wastewater treatment plants. Analysis of the “electrochemically active consortia” revealed that Geobacter sp., Desulfuromonas sp., Alcaligenes faecalis, Enterococcus faecium, Pseudomonas aeruginosa, Clostridium sp., Bacteroides sp., Aeromonas sp. and Brevibacillus sp. are detected in the mixed cultures. The mixed-cultured MFCs have shown to produce more power than those with pure cultures, possibly due to the following properties the consortia possess: a higher resistance against process disturbances; a greater substrate versatility, and a higher power output[ref 2, 3, 4].
Considering all above, the most promising and economical method of MFC optimization is to find efficient microbes to metabolize biomass. Several approaches have been used to select or construct the efficient electrogenic organisms.
Study and Improve Current Electrogenic Organisms
One approach is to study the mechanisms of electron transfer between the currently known electrogenic organisms and the electrode. The ultimate goal is to optimize MFC performance either through better electrode design, or genetic engineering microbes to be efficient electricity producers. Geobacter and Rhodoferax (e.g. Rhodoferax ferrireducens) species, have the novel ability to directly transfer electrons to the surface of electrodes, which makes it possible to harvest electricity from waste organic matter. The energy metabolism under a variety of nutrient conditions of other representative electrogenic microbes such as Geobacter metallireducen, Shewanella oneidensis have also been investigated.
While a thorough understanding of the mechanisms behind the MFC technology is important, this approach only confined to a small set of organisms, and many more electrogenic microbes are left untapped or undiscovered. Besides, this approach is only focus on single bacteria strain, whereas mix-cultured consortia have been shown to be more efficient in MFC.
Experimentally Select and Enrich Organisms from Respective Wastewater Surrounding Environment
Another approach employed by most MFC labs is to experimentally select and enrich organisms in the anaerobic sewage sludge obtained from the surrounding area of the respective wastewater treatment plants. Anaerobic sewage sludge is usually a good source for inoculating a MFC due to its easy accessibility and rich content of varied bacterial communities that include electrochemically active bacteria, and other non-electrogenic microbes such as fermentative bacteria, methanogens, and sulfate reducers. However, the electrochemically active bacteria have been estimated to only comprise a small percentage of the total bacteria in activated sludge typically. Several rounds of enrichment process to increase the population of electrogenic microbes are usually necessary to reach satisfactory MFC performance. While this approach can obtain organisms which fit to the environment of the respective wastewater plants best, thus enrich the bacterial communities that digest the particular kind of wastewater most efficiently, the process is tedious and time-consuming, and unavoidable for all the different kind of wastewaters need to be treated.
Other than the bacteria mentioned above, there should be more new types of bacteria that are capable of anodophilic electron transfer (electron transfer to an anode) yet to be discovered[ref 2], and this is the area where this invention can help.
Systematically Selecting Organisms in Respect to Different Wastewaters Using an In Silico Screening Platform “Computer-Assisted Strain Construction and Development Engineering (CASCADE)”
The approach utilized this invention is to systematically select organisms in respect to different wastewaters using an In Silico screening platform “Computer-Assisted Strain Construction and Development Engineering (CASCADE)”, which is developed under a SBIR Phase II contract from the US Army, and an extension of an earlier system QIS D2 (Quantum Intelligence System for Drug Discovery) developed from DARPA SBIR Phase II Award (May 2004-May 2006): Development of Predictive Algorithms for In Silico Drug Toxicity and Efficacy Assessment. This project focuses on developing predictive algorithms for accurately predicting drug toxicity and efficacy from multiple data sources. A QIS D2 model can be successfully trained, tested and validated on evidence data sets (either experimental or logical) for predicting the potential in vitro or in vivo effects of drug molecules in biological systems, of particular interest are effects arising from chemical and biological agents and pathogens. QIS D2 system possesses the core capabilities of modeling the data from various sources, including data and text, and integrating them for drug discovery; of performing sensitivity analysis for biochemical targets of interest, of accurately predicting biochemical targets of interest using a large number of attributes. It is able to predict thousands of targets simultaneously. Likewise, the QIS D2 methodology has been applied in CASCADE development to understand why organisms are metabolically different based on their generic makeup.
By applying CASCADE, this invention is able to link massive genetic and chemical fingerprints in the metabolic and energy-generating biological pathways to assess an organism's metabolic capability to digest the organic matters, generate hydrogen, and electricity, at the same time to clean the wastewater. This makes it possible to customize and find efficient microbes (—or even to discover novel microorganisms) for hydrogen production, electricity generation and BOD (Biological Oxygen Demand) reduction based on the initial content of a wastewater, therefore it will drastically increase the conversion rates of both hydrogen and electricity productions.
The CASCADE platform can also apply to the applications in biological methane and chemical production during wastewater treatment. As shown in
This invention is a knowledge pattern learning and search system for selecting microorganisms to generate clean energy. The method is an in silico screening platform which involves three steps. First, the organisms' profiles are compiled by linking the massive genetic and chemical fingerprints in the metabolic and energy-generating biological pathways (e.g. codon usages, gene distributions in function categories, etc.) to the organisms' biological behaviors. Second, a machine learning and pattern recognition system is used to group the organism population into characteristic groups based on the profiles. Lastly, one or a group of microorganisms are selected based on profile match scores calculated from a defined metabolic efficiency measure, which, in term, is a prediction of a desired capability in real life based on an organism's profile. In the example of recovering clean energy from treating wastewaters from food process industries, domestic, animal or meat-packing wastes, microorganisms' metabolic capabilities to digest a required organic matter and generate clean energy are assessed using the invention, and the most effective organisms in terms of waste reduction and energy generation are selected based on the content of a biowaste input and a desired clean energy output. Thus, using a microorganism or consortia, clean hydrogen can be recovered from an anaerobic fermentation process accompanying the wastewater treatment, and the end products from the fermentation process can be fed into a Microbial Fuel Cell (MFC) process to generate clean electricity and at the same time treat the wastewater. The invention can be used to first select the microorganisms to efficiently generate hydrogen and select electrogenic organisms to convert the by-products into electricity.
The original goal of the invention is to recover clean energy from biowastes. Clean energy here refers to the renewable energy which has the maximum efficiency and minimal impact on the environment. Biowaste resources here, for example, food processing wastewaters, domestic wastes and animal wastes, are not only the economic resources for clean energy generation but also are needed to be treated and cleaned. The invention customizes and finds efficient microbes or microorganisms based on an initial content of a biowaste to extract energy and at the same time to treat the biowaste. The selected microorganisms are natural organisms in general. They can be used directly to produce desired clean energy. In addition, the invention can also be used to guide the bioengineering or alternation of the selected natural organisms for better efficiency. The system provides an efficient and sustainable method to generate clean energy at the same time offset the biowaste treatment costs. The invention also aims to reduce the experimental costs and justify the selection microorganisms before they are experimentally tested.
Step 1: Compile a profile: For a given organism, a given content of a biowaste input (202 and 124) and a desired clean energy output (206, 210), compile a profile for that organism, i.e. data or text that best describes the organism with respect to the input, output and its biological system as a whole. For example, data and text that describes a biological system as a whole can be gene similarity among organisms (112), genes' generic functions (118), genes' metabolic functions (120), biological pathways (114) and pathway substrates/products (124) involving energy-generation. This is done for the organisms in various databases such as KEGG, or the organisms metabolically reconstructed directly from genomic sequences, or the organisms in literature with other types of genetic information.
Step 2: Group the organism population. Apply a machine learning, data mining, text mining and pattern recognition method, such as Quantum Intelligence System (QIS) (122) to group the organism population into characteristic groups based on the profiles compiled in Step 1. QIS includes a set of data and text mining techniques integrating small, local and quantum intelligence into a global understanding.
Step 3: Apply a metabolic efficiency measure to match a profile. One or a group of microorganisms are selected based a profile match score. The score is calculated for each organism from a defined metabolic efficiency measure for the organism. A metabolic efficiency measure is a prediction of a desired capability in real life based on an organism's profile. A metabolic efficiency measure depends on the applications, for example,
We want to show an example of recovering clean energy from treating wastewaters from food process industries, domestic, animal or meat-packing wastes (202). Using a microorganism or consortia (212), clean hydrogen (206) can be recovered from an anaerobic fermentation process (214) accompanying the wastewater treatment, and the end products from the fermentation process such as acetic acid (acetate), butyric acids (butyrate), propionic acid, ethnol, lactate (204) can be fed into a Microbial Fuel Cell (MFC) process (208) to generate clean electricity (210) and at the same time treat the wastewater to become clean water (209), using the same or different microorganisms (212). The invention can be used to first select the microorganisms to efficiently generate hydrogen and select electrogenic organisms to convert the by-products into electricity.
The system can be installed on a ship, such as, a military ship or a commercial ship to processing the wastewaters on the ship. It cleans the water and also generates hydrogen, electricity, or methane to be used on the ship.
The system can be installed at a sugar plant, a brewery, a winery, a dairy, or beverage plants to process their wastewaters. These wastewaters contain higher sugar, grain, carbohydrates and other organic substances for energy to be extracted using this invention. In U.S. alone, there are about 24,000 such factories which will need wastewater treatments or recycles.
The system can be installed on a site of municipal wastewater treatment facilities to clean the water and generate clean energy to cover current expensive aerating process.
The system can be installed on a farm for animal waste treatments to generate cleaner energy than the current biogas generation process.
The benefit of provisional patent application No. 60/935,159, filed Jul. 27, 2007, and provisional patent Application No. 60/964,207 filed Aug. 10, 2007 under 35 U.S.C. 119(e), are hereby claimed.
The invention was supported in part by US Army Small Business Innovation Research contract No. CBD W911NF-06-C-0056 and contract No. W911NF-07-C-0039 with Chemical Biological Defense (CBD) of US Army Research Office
| Number | Date | Country | |
|---|---|---|---|
| 60935159 | Jul 2007 | US | |
| 60964207 | Aug 2007 | US |
