Construction Biotechnology

Microorganisms (microbes) are organisms that are not visible without aid of microscope and can be found in all five kingdoms of living creatures on Earth: Bacteria, Archaea, Fungi, Plants, and Animals, but mainly first kingdom is used in Construction Biotechnology because of smallest size, highest growth rate, and diverse biogeochemical and biosynthetic activities of bacteria. Selection of needed bacterial strain for the biosynthesis of construction material or performance of construction process can be done either theoretically using the periodic table of physiological classification of prokaryotes, or through the experimental selection of enrichment culture following with isolation and identification of pure culture. Microbiology of Construction Biotechnology process requires understanding and strict performance of the biosafety rules aiming to prevent outbreaks of the infectious diseases during the production of construction biomaterials or application of microorganisms in construction process. Fungi and aerobic Gram-negative bacteria are most active in the biosynthesis of cement admixtures and bioplastics. Facultative anaerobic and anaerobic Gram-positive bacteria are most suitable for cementation and clogging of the porous soil and fractured rocks under high or changeable osmotic pressure. Phototrophic cyanobacteria and algae are most suitable for the biocrust formation on the soil surface. Understanding of microbiology is essential in the development of biotechnological construction material or biotechnological construction process but the commercial biomaterial or bioprocess must be made so that there will be sufficient just instruction for user. However, geotechnical or environmental applications of microbial processes in the field may require due to complexity of the factors or either partnership with microbiologist or understanding of the basic principles of microbiology.

Construction Biotechnology is a scientific and engineering knowledge on the use of microorganisms or their products for construction processes or production of construction materials. All biotechnological processes include: (1) a preliminary step (upstream); (2) a cultivation and biogeochemical activity (core process); (3) a posttreatment step (downstream); and (4) process monitoring and control. Isolation and selection of proper pure or enrichment culture for bioprocess is the most essential preliminary step. Batch or continuous cultivation of microorganisms in bioreactor or in soil must be maintained by the optimal supply of nutrients, proper electron donor and acceptor, temperature, pH, salinity, and other factors essential for growth and biosynthetic or biogeochemical activities of microbial cells. Understanding of biotechnology is essential in the development of biotechnological construction material or biotechnological construction process but the commercial biomaterial or bioprocess must be made so that there will be sufficient just instruction for user. However, geotechnical or environmental applications of biotechnological processes in the field may require due to complexity of the factors or either partnership with biotechnologist or understanding of the basic principles of biotechnology.

Functional biopolymers of cell are proteins, RNA and DNA, which are fast producing and biodegrading. Energy storage polysaccharides, polyhydroxyalkanoates, as well as lipids are producing and degraded slower. Structural biopolymers are cellulose, hemicellulose, chitin of cell wall, and polysaccharides of cell wall and capsule, biodegrading slowly. Microbial extracellular polysaccharides are widely using in cement- and gypsum-based materials to improve such properties of the material as plasticity, water retention, adhesion, shrinkage reduction, flow ability, and stability. Probably, the biopolymers of sewage sludge and activated sludge wastes can be used as the cement admixtures, because several million tons of these materials are available as wastes. Production of polysaccharide admixtures could be more sustainable if it will be performed on the biorefinery. The common products of any fermentation on biorefinery or pyrolytic transformation of wood to fuel—ethanol, acetic acid, and hydrogen—are the most useful substances for the production of biocements, biogrouts, bioplastics, and polysaccharide admixtures. Ethanol is one of the best sources of carbon and energy for the production of polysaccharide admixtures.

Plastics that are used in the construction industry produce hazardous nonbiodegradable wastes after demolition of the buildings or temporal constructions. Recent investigations on bioplastic reveal a new and sustainable construction bioplastics made from the renewable organic sources that can be left in soil or composted after demolition because of their biodegradability. Bioplastics also have the potential to lead to the rise of new building materials with low embodied energy thus contributing to energy building efficiency. Cheap raw materials, continuous, and nonaseptic cultivation of mixed bacterial culture, and production of crude composite bioplastic as construction material with low embodied energy has to be used to enhance bioplastic cost-efficiency. Bioplastic can be produced as by-product of biorefinery using acidogenic fermentation or pyrolysis of lignocellulosic biomass, as well as by-product of biotreatment of solid or liquid municipal wastes.

The chemical reactions and physical processes of biogeochemical cycles of carbon, nitrogen, calcium, magnesium, phosphate, iron, silicon are used for the construction bioprocesses. Microbial oxygenic photosynthesis can be used in construction biotechnology for the formation of soil crust to control dust release, to stop sand dunes movement, and to immobilize atmospheric dispersion of soil surface pollutants, for example radioactive substances. Microbial anoxygenic photosynthesis could be used in construction biotechnology for the removal of H₂S from water or from biorestoration of marble historical sculptures or constructions deteriorated by the black precipitate of CaS produced by bacterial sulfate reduction of sulfur oxides from polluted air. Acidogenic fermentation could be used in construction biotechnology for the production of organic (mainly acetic) acid and dissolution of calcium carbonate, magnesium carbonate, or iron (hydr)oxide with the formation of soluble salts of Ca, Mg, and Fe. Urease-inducing or aerobic oxidation of calcium salts of organic acids can be used further for bioaggregation, bioclogging, and biocementation of porous soil or fractured rocks due to calcium carbonate precipitation. Oxidation of ammonium to nitric acid is one of the important factors of biocorrosion of metals and biodeterioration of concrete and marble. Biomediated formation of carbonate, phosphate, and silicate minerals of calcium, iron, and magnesium is the prospective way for production of construction materials and the performance of the construction processes. Some of them are used in construction but many of these potentially useful bioprocesses were not discovered and studied yet.

The biotechnological production of construction biomaterials is a sustainable process because renewable agricultural and biotechnological biomass residues are used as organic raw materials and as the components of composite biocement. In some geotechnical processes, microorganisms themselves are performing useful function. There are at least eight types of construction-related biotechnological processes classified by the results of the microbial treatment of soil: bioaggregation of soil particles, biocrusting of soil surface, biocoating of solid surface, bioclogging of soil, porous material or fractured rocks, biocementation of soil or porous material, biodesaturation of soil, bioencapsulation of clay/soft soil/particles, and bioremediation of polluted ground.

Cement is an energy-consuming construction material with environmentally unfriendly production. Due to the high viscosity of cement paste it cannot be used for the grouting. New construction material, microbial biocement can be produced either from limestone or dolomite or from calcium salt chloride solution at ambient temperature. Dry biocement can be dissolved and as solution of low viscosity can be sprayed over, injected in, or percolated through the porous soil for its strengthening. This strengthening is applicable to enhance stability of the slopes and dams, for road construction, prevention of soil erosion, for the construction of the channels, aquaculture ponds, reservoirs, landfills in sandy soil, to reinforce sand in near-shore areas, for the remediation of cracks in concrete and the self-remediation of concrete, consolidation of porous stone and fractured rocks, the bioremediation of weathered-building stone surfaces, the fractured rock permeability reduction, the mitigation of earth quake-caused soil liquefaction, the encapsulation of soft soil, the coating of surfaces with calcite for protection of concrete from corrosion and for enhanced marine epibiota colonization. The concept of bacterial self-healing is under question because only 30 % of the concrete cracks volume can be filled by calcite produced from 5 % (v/v) of introduced into concrete capsules.

Grouting is a process to fill the soil voids with fluid grout, which is used to control water flow in soil. Such common grouts as solutions or suspensions of sodium silicate, ultrafine cement, acrylates, acrylamides, and polyurethanes have such disadvantages as high viscosity and low depth of penetration in soil, high cost, and toxicity. Bioclogging or biogrouting is either using formation of microbial biopolymers or microbially induced precipitates of inorganic compounds in situ for water flow control. Biogrouting includes formation of impermeable layer of algal and cyanobacterial biomass; production of slime in soil by aerobic and facultative anaerobic heterotrophic bacteria, production of undissolved sulfides of metals by sulfate-reducing bacteria; formation of undissolved carbonates of metals by ammonifying bacteria and urease-producing bacteria; production of ferrous solution by iron-reducing bacteria, and precipitation of undissolved ferrous and ferric salts and hydroxides in soil by iron-oxidizing bacteria; self-decay of calcium bicarbonate with formation of calcium carbonate clogging. Bioclogging can be applied to diminish piping of the slopes and dams, prevention of soil erosion, construction of the channels, sealing of the aquaculture ponds, reservoirs, landfills, tunneling space before and after excavation in sandy soil or sedimentary rocks, and sealing of the sedimentary and fractured rocks.

Construction Biotechnology can be used for ground surface fixation of soil particles to control water and wind erosion of soil, to control dust and dispersion of radioactive, chemical, and bacteriological pollutants in atmosphere, to mitigate the dune movement and dust storms in sand deserts, and to seal the surface of ponds, channels, reservoirs, and landfills to diminish seepage of water. After biotreatment of the fine sand with the dosage of precipitated Ca 15.6 g/m², the release of the sand dust and its artificial pollutants to atmosphere decreased in comparison with control by 99.8 % for dust, 92.7 % for phenantherene, 94.4 % for led nitrate, and 99.8 % for bacterial cells of Bacillus megaterium. The calculated consumption of calcium during construction of model pond was 0.7 kg Ca/m² for biocementation by spraying, 1.2 kg Ca/m² for biocementation through precipitation of calcite from the covering solution, and 0.2 kg Ca/m² was used for the biocementation of the small cracks in the dried model pond.

Biocoating of concrete with a layer of calcium carbonate crystals can be performed using urease-producing bacteria, calcium salt, and urea. The calcium carbonate biocoating of the concrete surface could protect the concrete constructions in marine environment from reactions of magnesium and bicarbonate ions with the calcium silicate hydrate gel of concrete. Additionally, it promotes colonization of the calcium carbonate-coated surface with epibiota, so calcium carbonate biocoating can be used for the construction of artificial coral reefs or water purifying epiphytic biosystems. Biocoating changed surface properties of recycled concrete aggregates, so they can be bound with asphalt mixture. Biocoating of concrete and stone surfaces is significantly affected by the gravitational precipitation of bacterial cells and carbonate crystals. The content of adhered calcite crystals on the vertical concrete surface was about 3 % of those on the horizontal surface of concrete. Similarly, the contents of adhered calcium carbonate crystals on the polished surfaces of the horizontal granite plates after flow of biocoating solution between them were 113 and 17 mg CaCO₃/cm² for the floor and ceiling plates, respectively. So, to coat the surface of concrete object by even layer of calcium carbonate crystals on all sides the object must be slowly rotated in the treatment tank. Different calcium carbonate crystals—prisms of calcite, spheres of vaterite, needles of aragonite, rose-shaped or other shapes of minerals—are formed in the coating layer depending on the conditions of treatment. Gravitational precipitation of both bacterial cells and calcium carbonate crystals, that ensured some contact time between particles and coated surface, is an essential step in their adhesion to this surface and formation of biocoating layer. Calcium carbonate biocoating could be cheaper, more sustainable, environment friendly, and more aesthetical than any other types of the concrete surface coating. Biocoating could be used for decoration of the concrete surface, for the manufacturing of the artificial coral reefs as well as the frames for shellfish aquaculture. Other materials such as wood, plastic, glass, clay can be also coated with the calcium carbonate layer using biotechnology. It is possible to coat the surface of concrete, rocks, wood, stems and leaves of the terrestrial plants, and the plastic materials with the layer of calcite using microbially induced calcium carbonate precipitation (MICP) to enhance colonization of these surfaces with larvae of corals and shells as well as with microscopic algae and photosynthetic bacteria.

Soil, surface water, groundwater, and atmosphere on the construction sites are often contaminated by pollutants, which are toxic substances for human, animals, and plants. There are known physical and chemical methods of the remediation of polluted soil but biological methods are often most cost effective but usually much slower than physical and chemical methods. Bioremediation of the polluted construction site can be performed in situ, on site or off site. Bioaggregation of soil particles using microbially induced calcium carbonate precipitation (MICP) can be used to control water erosion of sand and the release of the sand-associated pollutants to environment. Small dosage of precipitated calcium, 6.4 g/m² of sand or 9 g Ca/kg of sand can diminish erosion of sand as well as release of chemical pollutants by three times and release of bacteriological pollutant by 10 times. Dosage of precipitated calcium by MCP of 0.8 g/kg of coarse sand decreased the content of lead in the removed coarse sand by 50 % of initial content. MICP co-precipitate radionuclides ⁹⁰Sr, ⁶⁰Co, and metal contaminants such as Cd and this can be used to prevent their dispersion in environment. Specific case of ground improvement is partial soil biodesaturation that diminishes the risk of soil liquefaction and accompanying damages of infrastructure during the earthquake. Biogas bubbles produced by denitrifying bacteria decrease water saturation of sand and risk of saturated sand liquefaction. MICP can be used to stabilize the biogas bubbles in the sand pores. However, the biogas bubbles can be removed from sand by water flow, while the biosealed biogas bubbles became stable. The sequential biogas production in saturated sand and biosealing of the gas bubbles in sand pores could be useful for sustainable mitigation of sand liquefaction in case of groundwater upflow through saturated sand.

New types of construction material, biocement, or biogrouts, are developing extensively as an alternative to cement and chemical grouts. Biocement/biogrout forms calcium carbonate minerals due to activity of urease-producing bacteria (UPB) in the presence of urea and calcium ions. So, UPB play a role of a bioagent in the biocementation. The important task is the development of biotechnology to produce UPB biomass for large-scale biocementation/bioclogging applications. Hydrolyzed activated sludge can be used as a cheap medium for cultivation of urease-producing bacteria. Bacteria Yaniella sp. VS8 produced inducible urease and Bacillus sp. VS1 produced constitutive urease. Biomass of both strains can be grown in the cheap medium from hydrolyzed activated sludge without any supplementary components for large-scale applications of biocementation.

Prevention of biodeterioration, biocorrosion, and biofouling of the construction materials is a task of Construction Biotechnology. Almost all construction materials can deteriorate due to microbial oxidation/reduction of C-, Fe-, S-, and N-containing compounds, hydrolysis of cellulose and hemicellulose of timber, production of organic and inorganic acids or alkali, and generation of oxygen radicals. Wood and paper can be easily biodegraded by the microorganisms under humid conditions. Objects of art, sculptures, and historical buildings are also deteriorated by microorganisms in humid and polluted atmosphere. Such organic acids as formic, acetic, propionic, butyric, lactic, gluconic, and other acids produced by bacteria during fermentation and fungi during oxidation, as well as sulfuric and nitric acids produced by bacterial oxidation are active corrosive agents. Microorganisms can induce corrosion by stimulation of the anodic reaction; formation of acids, by stimulation of the cathodic reaction, microbial production of H₂S; by the biodegradation of protective films, and by increase of conductivity of the liquid environment. All microbially caused problems can be controlled by: (1) biocides; (2) maintenance of the conditions unfavorable for microbial growth and activity, for example, low humidity and water content, and absence of electron donors and acceptors; (3) conventional corrosion control methods. Chemical biocides and preservatives are widely used in all industries. Environmentally friendly biotechnological preservatives for timber are developing. Negative role of microorganisms in constructions is also formation of bioaerosol, which is a collection of airborne biological particles such as viruses, cells of bacteria, spores of fungi, cells of algae, with the size ranged from 0.1 to 30 μm. To prevent production of aerosols the selection of proper materials, humidity, ventilation, and air conditioning conditions must be made, and in the cases when infectious agent is present in air, disinfection of this air by UV light or purification of air by adsorption filtration through activated carbon of fine fibers must be made, and a source of pathogens has to be removed or eliminated.

Current status for biotechnological construction materials is as follows: (1) admixtures for cement are produced commercially, used widely in practice, and new biotechnological admixtures are developing for industrial use; (2) bioplastic PLA is produced industrially, but construction applications are still in development because of relatively high cost of this bioplastic; (3) bioplastic PHAs are still developing in the pilot scale for industrial production and applications; (4) biotechnological nanomaterials for construction are still studied in laboratory scale; (5) biotechnological preservatives for timber are still studied and tested in pilot scale; (6) different types of biocements and biogrouts are tested in laboratory and pilot scale; (7) biogrouts for soil desaturation and mitigation of soil liquefaction are still in the stages of laboratory studies and pilot tests. New products and applications of construction biotechnology could be developed and used in practice: (1) environmentally safe and low cost biogrouts for bioclogging of the tunneling space before or after excavation; (2) environmentally safe and low cost biogrouts for bioclogging of aquaculture ponds, water reservoirs, channels, landfills, soil-polluted sites; (3) commercially available bioimmobilizers of arid desert sand surface, for dust and soil surface pollutants control, and soil erosion control; (4) commercially available biocoating materials and acceptable technologies of their application; (5) commercially available biogrouts and technologies of their application for partial soil desaturation and mitigation of soil liquefaction; (6) development of low cost biocements producing low brittleness cemented materials; (7) low cost admixture to cement from sewage sludge or activated sludge of municipal wastewater treatment plants; (8) environmentally safe and low cost production of biocements and biogrouts from limestone, dolomite, cement dust, and other cement-related materials on the cement plants; (9) development of biomimetic, 3D composite biotechnological construction materials; and many other materials, technologies, and their applications.