Microorganism loaded aggregate and manufacturing methods

Abstract

The invention is directed to compositions, tools and methods for the manufacture of construction materials, masonry, solid structures and compositions to facilitate dust control. More particularly, the invention is directed to the manufacture of bricks, masonry and other solid structures using small amount of aggregate material that is pre-loaded with spores and/or vegetative bacterial cells.

Description

BACKGROUND

1. Field of the Invention

The invention is directed to compositions, tools and methods for the manufacture of construction materials. More particularly, the invention is directed to the manufacture of bricks, masonry and other solid structures, and dust control using aggregate materials loaded with spores and/or vegetative microorganisms to initiate and/or standardize the manufacturing process which may be utilized in large-scale production.

2. Description of the Background

Traditional brick and concrete construction is heavily reliant on burning natural resources such as coal and wood. This reliance results in the consumption of massive amounts of energy resources and equally massive carbon dioxide emissions, thus a great dependency on limited energy sources. An alternative to these traditional processes involves a process known as microbial induced calcite precipitation (MICP). MICP comprises mixing urease and urea as a source of energy with an aggregate material such as, for example, sand. The enzyme catalyzes the production of ammonia and carbon dioxide, increasing the pH level of the composition. The rise in pH forms a mineral “precipitate,” combining calcium with carbon dioxide. Particles present in the mixture act as nucleation sites, attracting mineral ions from the calcium forming calcite crystals. The mineral growth fills gaps between the sand particles biocementing or bonding them together. Preferably, the particles contain gaps of at least 5 microns in width, but can be larger or smaller as desired. The resulting material exhibits a composition and physical properties similar to naturally formed masonry, bricks or other solid structures. Hardness can be predetermined based at least on the structure of the initial components and the pore size desired.

Enzyme producing bacteria that are capable of biocementation include Sporosarcina ureae, Proteus vulgaris, Bacillus sphaericus, Myxococcus xanthus, Proteus mirabilis, or Helicobacter pylori, although proper concerns should be given to pathogenic strains. Combinations of any of these strains as well as functional variants, mutations and genetically modified stains may be used as well. Bacterial compositions contain nutrient media to maintain and/or allow the cells to flourish and proliferate. The various types of nutrient media for cells, and in particular, bacterial cells of the invention are known and commercially available and include at least minimal media (or transport media) typically used for transport to maintain viability without propagation, and yeast extract, and molasses, typically used for growth and propagation.

This method for manufacturing construction materials through induced cementation exhibits low embodied energy, and can occur at ambient pressure, and in a wide range of temperatures. The ambient temperature and conditions as well as the content of available aggregate can determine whether pure enzyme, lyophilized enzyme, or live cells are utilized as the starting components. Generally, live cells are used in warmer temperatures where mild weather conditions exist, whereas pure enzymes can be advantageous at more extreme conditions of cold or heat. The introduction of a bioengineered building unit using sand aggregate and naturally induced cementation provides a natural alternative that may be locally produced and environmentally friendly. As little to no heating is necessary, the energy savings in both expenses and efficiency is enormous.

The initial ingredients needed for MICP are readily available. Sources of calcium are often locally available from, for example, local geology such as limestone, milk and milk products and by-products, egg shells, lakes and rivers, sea water, and plant materials to name a few. Calcium is used as a source when in the form of a salt such as, preferably, calcium chloride, calcium carbonate, calcium lactate, calcium acetate, calcium phosphate and calcium sulfate. Many of these forms are readily available in different parts of the world. Also readily available in most parts of the world is urea. As a chemical salt, it can be easily obtained from urine which is available from livestock and agricultural sources, as well as municipal sources. Thus, compositions of the invention may include a calcium source and/or urea, and/or the calcium source and/or urea may be obtained separately.

Another advantage of MICP is that the process can be utilized in both small and large scale, and also easily automated. The bulk content of the masonry manufacturing process of the invention can be most any material that is locally available including rocks, sand, gravel and most any type of stone. Processing of the stone, such as crushing or breaking into pieces, also can be performed locally. Thus, transport costs and expenses are minimized The composition of the invention (which may be provided lyophilized and hydrated on site), the frame for the bricks (if otherwise unavailable), and instructions as appropriate are all that need to be provided. If shipping is required, this represents a tiny fraction of the delivery costs, especially as compared to the present expenses associated with the delivery of conventional cement.

Another advantage of this invention is to produce a “grown” construction material, such as a brick, utilizing primarily minerals, MICP and loose aggregate, such as sand. Not only can bricks and other construction materials be created, but the bricks themselves can be cemented into the desired places using the composition of the invention to “cement” the bricks to one another and/or to other materials thereby forming the buildings, support structure or member, walls, roads, and other structures.

Biologically grown bricks and masonry do not require the traditional use of Portland cement mortar, which enables the reduction of atmospheric carbon dioxide by offering an alternative to the high-embodied energy traditionally manufactured construction materials. Employing cells to naturally induce mineral precipitation, combined with local aggregate and rapid manufacturing methods enables the production of a local, ecological, and economic building material for use throughout the global construction industry.

Although MICP can be utilized to create nearly any form of brick, block or solid structure used in construction, efficient methods for large scale manufacture have yet to be developed. Thus, a need exists for a rapid and convenient process that provides consistency to the manufacture of masonry that is both economical and environmentally safe.

SUMMARY OF THE INVENTION

The present invention overcomes problems and disadvantages associated with current strategies and designs, and provides new tools, compositions, and methods for the manufacture of building materials.

One embodiment of the invention is directed to methods comprising: adding an aqueous medium to a collection of viable spore-forming bacteria forming an aqueous mixture; incubating the aqueous mixture under conditions that promote or specifically induce spore formation or vegetative cell formation; mixing spores and/or vegetative cells with aggregate particles forming a slurry; and concentrating the spores and/or vegetative cells by removing at least a portion of liquid which is mostly water. Preferably the aqueous medium is at a physiological pH, promotes spore formation, comprises one or more of salts, amino acids, proteins, peptides, carbohydrates, saccharides, polysaccharides, fatty acids, oil, vitamins and minerals, and does not contain urea. Preferably the viable spore-forming bacteria comprise one or more strains of Sporosarcina pasteurii, Sporosarcina ureae, Proteus vulgaris, Bacillus sphaericus, Myxococcus xanthus, Proteus mirabilis, Bacillus megaterium, Helicobacter pylori, and/or any urease and/or carbonic anhydrase producing microorganism. Preferably incubating is performed at from about 25-40° C. and for about 6 hours to about 6 days, more preferably for about 1-3 days. Preferably mixing further includes addition of a binding agent. Preferred binding agents promotes adhesion between spores and/or vegetative cells and aggregate via, for example, hydrophobic bonds, hydrophilic bonds, ionic bonds, non-ionic bonds, covalent bonds, van der Waal forces, or a combination thereof, and may comprise a polymer, a saccharide, a polysaccharide, a carbohydrate, a fatty acid, an oil, an amino acid, or a combination thereof. Preferred aggregate particles comprise natural, non-natural, recycled or manufactured sand, ore, crushed rock or stone, minerals, crushed or fractured glass, mine tailings, paper, waste materials, waste from a manufacturing process, plastics, polymers, roughened materials, and/or combinations thereof, wherein aggregate particles are in the form of beads, grains, strands, fibers, flakes, crystals, or combinations thereof. Preferred particle sizes or average diameters will pass through a mesh size of 100 or smaller, or more preferably a mesh size is 200 or smaller. Removal of an aqueous component is preferably accomplished by evaporation, heat-assisted evaporation, filtration and/or vacuum-assisted filtration and/or

an aqueous liquid may be added to the concentrated slurry. Preferably the slurry contains from about 10¹⁰ to about 10¹⁵ spores and/or vegetative cells/ml.

Another embodiment of the invention comprises spore-loaded aggregate made by the methods of the invention. Preferably the spore-loaded aggregate contains less than about 50% liquid by weight, less than about 10% liquid by weight, less than about 5% liquid by weight, or no liquid. Spore-loaded aggregate or dried spore-loaded aggregate may be supplemented with additional aqueous liquid, such as but not limited to water, PBS or saline. Preferably spore-loaded aggregate contains from about 10⁶ to about 10¹² spores and/or vegetative cells/ml.

Another embodiment of the invention is directed to method of manufacturing construction material, solid structures, or the manufacture of compositions to utilize for dust control applications comprising: combining in any order a spore-loaded aggregate composition of the invention with urea, calcium, additional aggregate material, which may be the same or different, and an incubation medium forming a mixture; incubating the mixture under conditions that promote formation of calcium carbonate; and forming the construction material. Incubation of the mixture may be in a formwork, which may be a fixed or powdered solid material, or after extrusion in the absence of a formwork. Preferably the construction material comprises bricks, thin bricks, pavers, panels, tile, veneer, cinder, breeze, besser, clinker or aerated blocks, counter- or table-tops, design structures, blocks, or a solid masonry structure. Also preferably the calcium is provided from calcium chloride, calcium acetate, calcium phosphate, calcium carbonate, calcium lactate, calcium nitrate, or a calcium salt, the aggregate material comprises natural, non-natural, recycled or manufactured sand, ore, crushed rock or stone, minerals, crushed or fractured glass, wood, ash, foam, basalt, fibers, mine tailings, paper, waste materials, waste from a manufacturing process, plastics, polymers, roughened materials, and/or combinations thereof, and incubation promoting proliferation of urease-producing vegetative cells.

Another embodiment of the invention is construction material and dust control compositions manufactured by the methods of this disclosure.

Other embodiments and advantages of the invention are set forth in part in the description, which follows, and in part, may be obvious from this description, or may be learned from the practice of the invention.

DESCRIPTION OF THE INVENTION

The manufacture of masonry and other building materials using a process known as microbial induced calcite precipitation (MICP) has been extensively described in a number of U.S. Patent (e.g., see U.S. Pat. Nos. 8,728,365; 8,951,786; 9,199,880; and 9,428,418; each of which is incorporated in its entirety by reference). In these processes, urease-producing cells or urease enzymes are mixed with aggregate and incubated with urea and a calcium source. Calcite bonds form between aggregate particles resulting in a solid structure. Although the process allows for the manufacture of building materials, manufacturing generally requires standardization for the purpose of large-scale production.

It has been surprisingly discovered that the manufacture of biologically-created solids can be standardized and, accordingly the manufacturing process enhanced. Standardization is achieved by adding an aqueous medium to a collection of viable spore-forming bacteria forming an aqueous mixture and incubating the aqueous mixture under conditions that promote spore formation. Spores of most urease-producing microorganisms are generally round, oval or slightly elongated with sizes from about 0.9 μm to 2.0 μm in length and from about 0.5 μm to about 1.0 μm in width. Spores and/or vegetative cells are then mixed with aggregate particles, preferably but not necessarily aggregate consistent with and/or similar to the bulk aggregate, forming a slurry and the slurry concentrated by the removal of at least a portion of the aqueous component, essentially the water, but not the spores and/or vegetative cells. Retention of spores and/or vegetative cells can be achieved by utilizing aggregate particles of a size or average size and composition that permits the transference of liquid such as water but retains spores and/or vegetative cells. These ultrafine aggregate particles can be maintained as a slurry or further liquid can be removed as desired to form a powder or solid structure.

One embodiment of the invention is directed to a method for forming starter cultures of spores and/or vegetative cells and aggregate material for the manufacture of solid structures, construction materials, or the manufacture of compositions to utilize for dust control applications (e.g., U.S. Pat. No. 8,951,786 issued 10 Feb. 2015; U.S. Pat. No. 9,428,418 issued 30 Aug. 2016; U.S. Patent Application Publication No. 2016/0264463 entitled “Compositions and Methods for Dust Control and the Manufacture of Construction Materials” published 16 Sep. 2016; U.S. Patent Application Publication No. 2016/0362334; each of which is entirely incorporated by reference). Spores and vegetative cells can be cultured from spore-producing bacterial and/or may be previously prepared and, preferably, under conditions that specifically induce the formation or spores or vegetative cells. The resulting solution or spore-containing or cell-containing culture is mixed with aggregate particles forming a slurry. Spores and/or vegetative cells (microorganisms) are concentrated from the slurry by removing at least a portion of liquid. Preferably the aggregate particles are largely or completely of a mesh size of 100 or smaller (particles of 150 μm or smaller), more preferably 200 or smaller (particles of about 75 μm or smaller) and more preferably 300 or smaller (particles of about 38 μm or smaller). Generally, particle sizes are measured or determined as average sizes. Water and dissolved aqueous materials can be removed and the microorganisms remain within the aggregate. In this way aggregate material can be loaded with a desired amount or quantity of microorganisms and stored. The microorganism-loaded aggregate particles can be maintained as a slurry, or dried as a powder or solid form. As the mixture contains aggregate and microorganisms, the mixture is relative resistant to variations in temperature or most any other external conditions, and therefore can be maintained for long periods of time. In this way, large numbers of spores and/or vegetative cells can be maintained to coordinate large manufacturing operations.

In a first step, spore-forming bacteria are cultured, preferably under conditions that promote spore and/or vegetative cell formation. Culture conditions include an aqueous medium comprising one or more of salts, amino acids, proteins, peptides, carbohydrates, saccharides, polysaccharides, fatty acids, oil, vitamins and minerals. Preferably, the aqueous medium does not contain urea, which will stimulate spore formation of the bacteria. Preferred spore-forming bacteria comprise one or more strains of Sporosarcina pasteurii, Sporosarcina ureae, Proteus vulgaris, Bacillus sphaericus, Myxococcus xanthus, Proteus mirabilis, Bacillus megaterium, Helicobacter pylori, and/or any urease and/or carbonic anhydrase producing microorganism. Bacteria are cultured in the aqueous medium, preferably at incubation is at a physiological pH and at temperatures of from about 25-40° C. Preferably incubation is performed from about 6 hours to about 6 days, more preferably for about 1-3 days, or as short a time as necessary to generate the desired number of spores and/or vegetative cells per bacterium.

Preferably spore formation or vegetative cell formation is induced, although an induction step is not required, and the microorganisms may be centrifuged or otherwise concentrated, and preferably resuspended into a paste with media or another suitable liquid that maintains the microorganisms without inducing further growth and/or proliferation (a status solution). Alternatively, microorganisms may be need mixed with aggregate without concentration, which may be preferable for manufacturing batches of vegetative cells.

Following spore-formation or vegetative cell formation as desired, cultures are mixed with aggregate particles. Aggregate particles may comprise natural, non-natural, recycled or manufactured sand, ore, crushed rock or stone, minerals, crushed or fractured glass, mine tailings, paper, waste materials, waste from a manufacturing process, plastics, polymers, roughened materials, and/or combinations thereof, and may be in the form of beads, grains, strands, fibers, flakes, crystals, or combinations thereof. Preferably the aggregate particles comprise particles with a mesh size of 100 or smaller (particles of about 150 μm or smaller), more preferably with a mesh size is 200 or smaller (particles of about 75 μm or smaller), or more preferably with a mesh size of 300 or smaller (particles of about 38 μm or smaller).

Preferably the aqueous mixture of spores and/or vegetative cells and/or the aggregate is combined with a binding agent that promotes the adhesion or retention of microorganisms and aggregate. Adhesion may be between microorganisms and aggregate via hydrophobic bonds, hydrophilic bonds, ionic bonds, non-ionic bonds, covalent bonds, van der Waal forces, or a combination thereof. Binding agents include, but are not limited to one or more of polymers, saccharides, polysaccharides, carbohydrates, fatty acids, oils, amino acids, or combinations thereof. Preferred binding agents are nontoxic and/or biodegradable and also preferably harmless to the spores and do not interfere or otherwise hinder eventual germination of spores or proliferation of vegetative cells.

Preferably the aqueous component and mixture is removed is by evaporation and/or filtration, such as, for example, heat-assisted evaporation, pressure-assisted filtration, and/or vacuum-assisted filtration. Following evaporation and/or filtration, the slurry or aggregate particles and microorganisms contains from about 10⁶ to about 10¹⁴ spores and/or cells/ml, preferably from about 10⁸ to about 10¹², and more preferably from about 10⁹ to about 10¹¹. The aqueous component can be further removed or removed entirely without hard to the spores and/or vegetative cells and the dried powder or block stored for future use in starting a culture of urease-producing bacteria.

Spore-containing aggregate material has a very long shelf life with greater than 80% viability after months and/or years with proper storage conditions. Vegetative-containing aggregate has a somewhat shorter shelf life with greater than 80% remaining viable after months and longer with proper storage conditions.

Another embodiment of the invention is directed to a composition comprising spore-loaded aggregate made by the methods of the invention. Preferably aggregate particles are of a mesh size of 100 or smaller (particles of about 150 μm or smaller), 200 or smaller (particles of about 75 μm or smaller), or 300 or smaller (particles of about 38 μm or smaller). Also preferably, the composition contains a binding or retention agent. The binding agent promotes adhesion between spores and/or vegetative cells and aggregate particles and/or the retention agent increases the size of aggregate particles and/or spores and/or vegetative cells, which promotes their retention.

Preferably the composition contains less than about 50% liquid by weight, more preferably less than about 10% liquid by weight, and more preferably less than about 5% liquid by weight. Preferred compositions contain from about 10¹⁹ to about 10¹⁵ spores and/or vegetative cells/ml.

Another embodiment of the invention is directed to methods of manufacturing construction material comprising combining in any order compositions of the invention with urea, calcium, an aggregate material, and an incubation medium forming a mixture. The mixture is incubated under conditions that promote formation of calcium carbonate which forms the solid structure of aggregate materials. Preferred solid structures include, for example, construction materials such as bricks, thin bricks, pavers, panels, tile, veneer, cinder, breeze, besser, clinker or aerated blocks, counter- or table-tops, design structures, blocks, or a solid masonry structure. Preferably the calcium is provided from calcium chloride, calcium acetate, calcium phosphate, calcium carbonate, calcium lactate, calcium nitrate, or a calcium salt. Also preferably the aggregate material comprises natural, non-natural, recycled or manufactured sand, ore, crushed rock or stone, minerals, crushed or fractured glass, wood, ash, foam, basalt, fibers, mine tailings, paper, waste materials, waste from a manufacturing process, plastics, polymers, roughened materials, and/or combinations thereof. Solid structures can be formed in a formwork or extruded as desired. Extruded aggregate retains a basic shape upon extrusion that solidifies over time into a solid structure at a desired hardness.

The following examples illustrate embodiments of the invention, but should not be viewed as limiting the scope of the invention.

EXAMPLES

Example 1

Spore Production

Sporosarcina pasteurii spores were produced from vegetative cells in culture media.

Example 2

Spore Loading

Spores (approximately 1 μm in diameter) were directly loaded into aggregate fines either by (1) vacuum-assisted or pressure-assisted filtration (or simply gravity assisted), or (2) evaporation. Alternatively, spore cultures may be concentrated and stored refrigerated in phosphate buffered saline (PBS) until ready for loading.

Method 1: Vacuum-Assisted Filtration

1. Whole spore cultures (2 L) were mixed with 1 kg ultrafine (<75 μm avg. diameter) manufactured aggregates.

2. A filtering apparatus was applied and the vacuum or a pressure engaged to facilitate liquid clearance.

3. Loaded fines were harvested and dried completely.

Method 2: Evaporation

1. Whole spore cultures (2 L) were mixed with 1 kg ultrafine (<75 μm avg. diameter) mining aggregates.

2. Spore aggregate mixtures were spread evenly over maximum surface area and dried under circulating air.

3. Loaded fines were harvested and dried completely. Spore loading aggregate from Method 1 demonstrated high retention of dormant spores within crude aggregate. Method 2 yielded a similar spore to aggregate distribution.

Other embodiments and uses of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. All references cited herein, including all publications, U.S. and foreign patents and patent applications, are specifically and entirely incorporated by reference. The term comprising, where ever used, is intended to include the terms consisting and consisting essentially of. Furthermore, the terms comprising, including, and containing are not intended to be limiting. It is intended that the specification and examples be considered exemplary only with the true scope and spirit of the invention indicated by the following claims.

Claims

1. A method of manufacturing a shelf-stable spore-loaded aggregate, the method comprising: (a) adding an aqueous medium to a collection of viable spore-forming bacteria to form an aqueous mixture;(b) incubating the aqueous mixture under conditions that promote the formation of spores and/or vegetative cells;(c) mixing the aqueous mixture incubated in (b) with aggregate particles; and(d) removing at least a portion of the aqueous medium to concentrate the spores or vegetative cells with the aggregate particles: (i) to a concentration of 106 to 1015 cells/mL and (ii) until the mixture contains less than 50% liquid by weight, to provide the shelf stable spore-loaded aggregate, which remains at least 80% viable after months of storage.

2. The method of claim 1, wherein the aqueous medium comprises one or more of salts, amino acids, proteins, peptides, carbohydrates, saccharides, polysaccharides, fatty acids, oil, vitamins and minerals.

3. The method of claim 1, wherein the aqueous medium does not contain urea.

4. The method of claim 1, wherein the viable spore-forming bacteria comprise one or more strains of Sporosarcina pasteurii, Sporosarcina ureae, Proteus vulgaris, Bacillus sphaericus, Myxococcus xanthus, Proteus mirabilis, Bacillus megaterium, Helicobacter pylori, and/or a urease and/or a carbonic anhydrase producing microorganism.

5. The method of claim 1, wherein the incubating is performed at from 25-40° C.

6. The method of claim 1, wherein the incubating is performed from 6 hours to 6 days.

7. The method of claim 6, wherein the incubating is performed for 1-3 days.

8. The method of claim 1, wherein the conditions comprise a physiological pH.

9. The method of claim 1, wherein the mixing further includes addition of a binding agent.

10. The method of claim 9, wherein the binding agent comprises a polymer, a saccharide, a polysaccharide, a carbohydrate, a fatty acid, an oil, an amino acid, or a combination thereof.

11. The method of claim 9, wherein the binding agent promotes adhesion between spores and/or vegetative cells and the aggregate particles via hydrophobic bonds, hydrophilic bonds, ionic bonds, non-ionic bonds, covalent bonds, van der Waal forces, or a combination thereof.

12. The method of claim 1, wherein the aggregate particles comprise natural, non- natural, recycled or manufactured sand, ore, rock, stone, minerals, crushed materials, fractured glass, mine tailings, paper, waste materials, plastics, polymers, roughened materials, and/or any combinations thereof.

13. The method of claim 1, wherein the aggregate particles are in the form of beads, grains, strands, fibers, flakes, crystals, or combinations thereof.

14. The method of claim 1, wherein the aggregate particles comprise particles with a mesh size of 100 or smaller.

15. The method of claim 14, wherein the mesh size is 200 or smaller.

16. The method of claim 1, wherein the concentration of the spores produced in (b) is from about 108 to about 1010 spores/mL.

17. The method of claim 1, wherein the aqueous medium stimulates spore formation.

18. The method of claim 1, wherein the aqueous medium maintains viability of the spore-forming bacteria without propagation.

19. The method of claim 1, wherein (d) concentrates the spores or vegetative cells with the aggregate until the mixture contains less than 10% liquid by weight.