Cyanobacterial Biocrust on Biomineralized Soil Mitigates Freeze-Thaw Effects and Preserves Structure and Ecological Functions.

Biocrust inoculation and microbially induced carbonate precipitation (MICP) are tools used in restoring degraded arid lands. It remains unclear whether the ecological functions of the two tools persist when these methods are combined and subjected to freeze-thaw (FT) cycles. We hypothesized a synergetic interaction between MICP treatment and biocrust under FT cycles, which would allow both components to retain their ecological functions. We grew cyanobacterial (Nostoc commune) biocrusts on bare soil and on MICP (Sporosarcina pasteurii)-treated soil, subjecting them to repeated FT cycles simulating the Mongolian climate. Generalized linear modeling revealed that FT cycling did not affect physical structure or related functions but could increase the productivity and reduce the nutrient condition of the crust. The results confirm the high tolerance of MICP-treated soil and biocrust to FT cycling. MICP treatment + biocrust maintained higher total carbohydrate content under FT stress. Our study indicates that biocrust on biomineralized soil has a robust enough structure to endure FT cycling during spring and autumn and to promote restoration of degraded lands.

Role of Na-Montmorillonite on Microbially Induced Calcium Carbonate Precipitation.

The use of additives has generated significant attention due to their extensive application in the microbially induced calcium carbonate precipitation (MICP) process. This study aims to discuss the effects of Na-montmorillonite (Na-MMT) on CaCO3 crystallization and sandy soil consolidation through the MICP process. Compared with the traditional MICP method, a larger amount of CaCO3 precipitate was obtained. Moreover, the reaction of Ca2+ ions was accelerated, and bacteria were absorbed by a small amount of Na-MMT. Meanwhile, an increase in the total cementing solution (TCS) was not conducive to the previous reaction. This problem was solved by conducting the reaction with Na-MMT. The polymorphs and morphologies of the CaCO3 precipitates were tested by using X-ray diffraction and scanning electron microscopy. Further, when Na-MMT was used, the morphology of CaCO3 changed from an individual precipitate to agglomerations of the precipitate. Compared to the experiments without Na-MMT in the MICP process, the addition of Na-MMT significantly reduced the hydraulic conductivity (HC) of sandy soil consolidated.

Transcriptome analyses reveal the utilization of nitrogen sources and related metabolic mechanisms of Sporosarcina pasteurii.

In recent years, Sporosarcina pasteurii (S. pasteurii) has become one of the most popular bacteria in microbially induced calcium carbonate precipitation (MICP). Various applications have been developed based on the efficient urease that can induce the precipitation of calcium carbonate. However, the metabolic mechanism related to biomineralization of S. pasteurii has not been clearly elucidated. The process of bacterial culture and biomineralization consumes a large amount of urea or ammonium salts, which are usually used as agricultural fertilizers, not to mention probable environmental pollutions caused by the excessive use of these raw materials. Therefore, it is urgent to reveal the mechanism of nitrogen utilization and metabolism of S. pasteurii. In this paper, we compared the growth and gene expression of S. pasteurii under three different culture conditions through transcriptome analyses. GO and KEGG analyses revealed that both ammonium and urea were direct nitrogen sources of S. pasteurii, and the bacteria could not grow normally in the absence of ammonium or urea. To the best of our knowledge, this paper is the first one to reveal the nitrogen utilization mechanism of S. pasteurii through transcriptome methods. Furthermore, the presence of ammonium might promote the synthesis of intracellular ATP and enhance the motility of the bacteria. There should be an ATP synthesis mechanism associated with urea hydrolysis catalyzed by urease in S. pasteurii.

Non-sterile corn steep liquor a novel, cost effective and powerful culture media for Sporosarcina pasteurii cultivation for sand improvement.

AIMS: Microbial induced calcium carbonate precipitation (MICP) is one of the bio-cementation methods for improving granular soils. This study evaluate the feasibility of obtaining a bacterial solution with high optical density and urease activity by an inexpensive corn steep liquor (CSL) medium in non-sterile conditions in order to achieve sand improvement. METHODS AND RESULTS: Corn steep liquor media with different concentrations (different dilution rates) were prepared and, without any autoclaving (non-sterile conditions), different percentage of the inoculum solutions were added to them and incubated. Effect of inoculum solution percentage and CSL dilution rates on specifications of bacterial solution was evaluated. Urease activity and scanning electron microscope (SEM) and X-Ray Diffraction (XRD) were used to efficiency of CLS media in sand improvement. The considerable urease activity was measured as 5·7 mS cm-1  min-1 using nonsterile CLS. By using CYNU (CSL-Yeast extract-NH4Cl-Urea) bacterial solution, the urease activity of 5·5 mS cm-1  min-1 for the OD600 (optical density at 600 nm) of 1·88 and, consequently, specific urease activity of 2·93 mS cm-1  min-1  OD600 -1 was obtained. The highest unconfined compressive strength (811 kPa) was obtained for the CYNU. XRD revealed new calcite peaks next to the quartz peaks. CONCLUSIONS: Production of inexpensive bacterial solution using diluted CSL as the inexpensive, effective and powerful culture media for Sporosarcina pasteurii cultivation in nonsterile conditions, allows geotechnical and biotechnological engineers to use MICP technology more widely in land improvement and field-scale bio-cementation and bioremediation projects. SIGNIFICANCE AND IMPACT OF THE STUDY: Obtaining high urease activity of inexpensive microbial solution using diluted CSL as the culture medium in nonsterile conditions, as the unique results of this study, can be significant in the field of bioremediation studies using MICP.

A Preliminary Study on Probiotic Characteristics of Sporosarcina spp. for Poultry Applications.

Probiotics are well known for their wide range of beneficial activities. However, recent use of probiotic Bifidobacterium, Enterococcus, and Lactobacillus spp. has been plagued by certain disadvantages such as complex growth requirements, high maintenance cost, susceptibility to the gastrointestinal environment, pathogenic gene transfer, non-standardized dosage, cell lysis at extreme acidic pH, widespread antibiotic resistance, and lower bacterial viability due to the lack of spore formation. Therefore, spore-forming bacteria belonging to Sporosarcina genus such as pasteurii, globispora, and psychrophila were assessed for probiotic characteristics such as biofilm formation, intestinal adhesion, acid and bile tolerance, antibiotic sensitivity, and anti-pathogenic activity. This ensures bacterial viability under gastrointestinal conditions and enabled the same to colonize effectively in the intestinal lumen (in vitro). The bacterial cell counts ranging from 6.59 to 6.91 log(CFU/mL) was observed for Sporosarcina spp. after 16 h. This indicated that there is no significant difference in the cell counts (P-value = 0.90). The cell counts of Sporosarcina spp. ranging from 5.57 to 5.93 log(CFU/mL) displayed strong acid tolerance at pH 2. They were also viable at higher bile (0.5%) concentration. Among the Sporosarcina spp., pasteurii showed better tolerance (6.90 log(CFU/mL)) even after 16 h. Among the selected bacteria, Sporosarcina psychrophila was more susceptible to teicoplanin and meropenem with an inhibition zone of 30 mm. Maximum antagonistic activity was observed against Serratia marcescens (with inhibition zone up to 15 mm). Our results suggest that bacteria belonging to Sporosarcina genus possess all the required characteristics to be used as potential poultry probiotics.

Sporosarcina pasteurii can form nanoscale calcium carbonate crystals on cell surface.

The bacterium Sporosarcina pasteurii (SP) is known for its ability to cause the phenomenon of microbially induced calcium carbonate precipitation (MICP). We explored bacterial participation in the initial stages of the MICP process at the cellular length scale under two different growth environments (a) liquid culture (b) MICP in a soft agar (0.5%) column. In the liquid culture, ex-situ imaging of the cellular environment indicated that S. pasteurii was facilitating nucleation of nanoscale crystals of calcium carbonate on bacterial cell surface and its growth via ureolysis. During the same period, the meso-scale environment (bulk medium) was found to have overgrown calcium carbonate crystals. The effect of media components (urea, CaCl2), presence of live and dead in the growth medium were explored. The agar column method allows for in-situ visualization of the phenomena, and using this platform, we found conclusive evidence of the bacterial cell surface facilitating formation of nanoscale crystals in the microenvironment. Here also the bulk environment or the meso-scale environment was found to possess overgrown calcium carbonate crystals. Extensive elemental analysis using Energy dispersive X-ray spectroscopy (EDS) and X-ray powder diffraction (XRD), confirmed that the crystals to be calcium carbonate, and two different polymorphs (calcite and vaterite) were identified. Active participation of S. pasteurii cell surface as the site of calcium carbonate precipitation has been shown using EDS elemental mapping with Scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM).

Sporosarcina pasteurii can clog and strengthen a porous medium mimic.

The bacterium Sporosarcina pasteurii can produce significant volumes of solid precipitation in the presence of specific chemical environments. These solid precipitate particles can enter a network of microscale pores and cause long-range clogging. As a result, the medium gains strength and exhibits superior mechanical properties. This concept is also known as Microbiologically Induced Calcite Precipitation (MICP). In this study, we have used sponge blocks as surrogate porous media mimics and analyzed several aspects of MICP. A synergistic approach involving electron microscopy (SEM), computerized X-Ray tomography (µCT), quasi-static compressive load testing and chemical characterization (EDX) has been used to understand several physical and chemical aspects of MICP.

Structural exploration of cinnamate-based phosphonic acids as inhibitors of bacterial ureases.

The conjugated system of cinnamic acid, α-substituted with a phosphonoalkyl residue, was previously validated as a scaffold that provided one of the most potent organophosphorus inhibitors of bacterial urease. Following the idea of using Morita-Baylis-Hillman adducts to introduce the terminal phosphonic side chain functionality to the α,ß-unsaturated system, we currently report the synthesis and activity of an extended series of compounds. Cinnamates modified with 3-phosphonopropyl and 4-phosphonobutyl side chains were obtained in a convenient two-step procedure, which involved Pd-mediated transformations of the Morita-Baylis-Hillman bromides as the key substrates. The introduction of a terminal alkenyl fragment, which was achieved by Stille coupling with stannanes, was followed by a tandem C-P bond formation/oxidation process. A submicromolar ligand of Sporosarcina pasteurii urease (Ki = 0.509 µM) was identified among the active molecules. In addition, inhibitors of Proteus mirabilis urease affected bacterial growth at the micromolar level. Based on the structure-activity relationship and the mechanism of inhibition, we suggest a nontypical mixed mode of action for the slow binding compounds. We presume that the molecular distance between the phosphonic group and the backbone double bond allows a dual activity: complexation of the acidic group with nickel ions and Michael addition of a cysteine forming the active site lid.

Modulation of fatty acid composition and growth in Sporosarcina species in response to temperatures and exogenous branched-chain amino acids.

Psychrotolerant endospore-forming Sporosarcina species have been predominantly isolated from minced fish meat (surimi), which is stored under refrigeration after heat treatment. To develop a better method for preserving surimi-based food products, we studied the growth and fatty acid compositions of the isolated strain S92h as well as Sporosarcina koreensis and Sporosarcina aquimarina at cold and moderate temperatures. The growth rates of strain S92h and S. koreensis were the fastest and slowest at cold temperatures, respectively, although these strains grew at a similar rate at moderate temperatures. In all three strains, the proportions of anteiso-C15:0 and unsaturated fatty acids (UFAs) were significantly higher at cold temperatures than at moderate temperatures. Furthermore, supplementation with valine, leucine, and isoleucine resulted in proportional increases in iso-C16:0, iso-C15:0, and anteiso-C15:0, respectively, among the fatty acid compositions of these strains. The proportions of the UFAs were also altered by the supplementation. At cold temperatures, the growth rates of strain S92h and S. koreensis, but not of S. aquimarina, were affected by supplementation with leucine. Supplementation with isoleucine enhanced the growth of S. koreensis at cold temperatures but not that of the other strains. Valine did not affect the growth of any strain. These results indicate that anteiso-C15:0 and UFAs both play important roles in the cold tolerance of the genus Sporosarcina and that these bacteria modulate their fatty acid compositions in response to the growth environment.

Stabilization of fly ash using cementing bacteria. Assessment of cementation and trace element mobilization.

Fly ash from municipal solid waste incineration (MSWI) was treated with microorganisms (Sporosarcina pasteurii and Myxococcus xanthus) to assess their capacity for cementing this waste material. Leaching tests on the samples treated with bacteria were also performed to assess the possibility of recovering and recycling trace elements from the fly ash. Sequential extractions combined with mineralogical studies demonstrated that Pb is mobile in water when associated with portlandite. Also, Cd, Pb, and Zn are primarily associated with carbonates and are mobile in acidic environments (up to 4.8, 13.9 and 248mg/l of Cd, Pb and Zn, respectively, extracted with acetic acid). Microbial treatment of the fly ash, especially with Sporosarcina pasteurii, led to its cementation and stabilization, preventing its dispersion into the environment. But samples treated with bacteria exhibited a higher capacity for trace element leaching than did untreated fly ash. The ability of these bacteria to mobilize metals can be applied to recover those of economic interest. The use of low cost biotechnologies can be an alternative to chemical treatments currently utilized for the recovery and reuse of these wastes.

Real-time monitoring of calcification process by Sporosarcina pasteurii biofilm.

Sporosarcina pasteurii is known to produce calcite or biocement in the presence of urea and Ca(2+). Herein, we report the use of novel ultramicrosensors such as pH, Ca(2+), and redox sensors, along with a scanning electrochemical microscope (SECM), to monitor a real-time, bacteria-mediated urea hydrolysis process and subsequent changes in morphology due to CaCO3 precipitation. We report that the surface pH of a live biofilm changed rapidly from 7.4 to 9.2 within 2 min, whereas similar fast depletion (10 min) of Ca(2+) was observed from 85 mM to 10 mM in the presence of a high urea (10 g L(-1)) brine solution at 23 °C. Both the pH and the Ca(2+) concentration profiles were extended up to 600 µm from the biofilm surface, whereas the bulk chemical composition of the brine solution remained constant over the entire 4 h of SECM experiments. In addition, we observed a change in biofilm surface morphology and an increase in overall biofilm height of 50 µm after 4 h of precipitation. Electron microscopy confirmed the changes in surface morphology and formation of CaCO3 crystals. Development of the Ca(2+) profile took 10 min, whereas that of the pH profile took 2 min. This finding indicates that the initial urea hydrolysis process is fast and limited by urease or number of bacteria, whereas later CaCO3 formation and growth of crystals is a slow chemical process. The ultramicrosensors and approaches employed here are capable of accurately characterizing bioremediation on temporal and spatial scales pertinent to the microbial communities and the processes they mediate.

Optimization of growth medium for Sporosarcina pasteurii in bio-based cement pastes to mitigate delay in hydration kinetics.

Microbial-induced calcium carbonate precipitation has been identified as a novel method to improve durability and remediate cracks in concrete. One way to introduce microorganisms to concrete is by replacing the mixing water with a bacterial culture in nutrient medium. In the literature, yeast extract often has been used as a carbon source for this application; however, severe retardation of hydration kinetics has been observed when yeast extract is added to cement. This study investigates the suitability of alternative carbon sources to replace yeast extract for microbial-induced calcium carbonate precipitation in cement-based materials. A combination of meat extract and sodium acetate was identified as a suitable replacement in growth medium for Sporosarcina pasteurii; this alternative growth medium reduced retardation by 75 % (as compared to yeast extract) without compromising bacterial growth, urea hydrolysis, cell zeta potential, and ability to promote calcium carbonate formation.

Alternative nutrient sources for biotechnological use of Sporosarcina pasteurii.

The potential use of Sporosarcina pasteurii in possible biotechnological applications on a large scale (ground improvement, consolidation of building structures and ornamental stone, or in developing bio-materials for the building industry), is based on its ability to produce high amounts of carbonate in a short period of time via urea hydrolysis. Industrial biomass production would have a low environmental impact and would be most economical if the standard growth media could be replaced with alternative nutrient sources, such as byproducts or wastes from other industries, or other low cost ingredients. The use of cost effective ingredients must guarantee ureolytic activities and growth conditions that are comparable to those resulting from the standard nutrient medium. In this work, three types of alternative media were tested for growing the ureolytic active bacteria S. pasteurii: (1) alternative nutrient sources such as industrial wastes resulting from the dairy and brewery industries, (2) fertilizer urea as an alternative urea substitute, and (3) different types of poultry manure based fertilizers as nutrient and urea substitutes. The comparison between the standard media, the nutrient alternatives and urea substitutes was possible by taking the protein concentration and nitrogen content into account. Bacterial activity was evaluated in terms of biomass changes over time (CFU, optical density, ATP measurements) and indirect estimation of the enzyme production (Nessler assay, conductivity measurement). The results revealed that some of the dairy wastes tested, such as whey and buttermilk, are potential alternative nutrients for bacterial development, while the urea fertilizer is perfectly suitable as an economical substitute for pure laboratory grade urea.

Effects of bentonite and yeast extract as nutrient on decrease in hydraulic conductivity of porous media due to CaCO3 precipitation induced by Sporosarcina pasteurii.

The reduction mechanism of hydraulic conductivity was investigated in porous media treated with bentonite and CaCO3 precipitates induced by growing cells of Sporosarcina pasteurii (ATCC 11859). Bentonite, the bacterial cells, and a precipitation solution, composing of 0.5 M CaCl2 and 0.5 M urea with or without 2% weight/volume yeast extract allowing the bacterial growth were sequentially introduced into the continuous-flow columns containing glass beads between 0.05 and 3 mm in diameter. The treatments reduced the hydraulic conductivity of the columns from between 8.4 × 10(-1) and 4.1 × 10(-3) cm/s to between 9.9 × 10(-4) and 2.1 × 10(-6) cm/s as the lowest. With yeast extract, the conductivity continuously decreased during four days of the experiment, while became stable after two days without yeast extract. Introduction of the bacterial cells did not decrease the conductivity. The reduction in hydraulic conductivity was inversely correlated with the volume occupied by the depositions of bentonite and CaCO3 precipitates in column, showing the same efficiency but a larger effect of the CaCO3 precipitates with increasing volume by bacterial growth. The smaller glass beads resulted in larger volume of the depositions. Bentonite increased the deposition of CaCO3 precipitates. Analysis using the Kozeny-Carman equation suggested that without yeast extract, bentonite and the CaCO3 precipitates formed aggregates with glass beads, thus increasing their diameter and consequently decreasing the pore size in the column. With yeast extract, in addition to the aggregates, the individual CaCO3 precipitates formed separately from the aggregates reduced the hydraulic conductivity.

Microbially induced calcite precipitation-based sequestration of strontium by Sporosarcina pasteurii WJ-2.

Contamination by radioactive strontium ((90)Sr) is a significant environmental problem. Ureolytically driven calcium carbonate precipitation has been proposed for use in geotechnical engineering for soil remediation applications. In this study, 68 ureolytic bacterial strains were newly isolated from various environments. Of these, 19 strains were selected based on ureolytic activity shown when cultured on urea agar plates and identified through 16S rRNA gene sequencing. From these selected strains, Sporosarcina pasteurii WJ-2 (WJ-2) was selected for subsequent study. A simple method was developed to determine the effectiveness of microbially induced calcite precipitation (MICP). Unlike any other methods, it does not require advanced skills and sophisticated tools. Using this method, we were able to determine the ability of the bioconsolidated sand to retard the flow of crystal violet through the 25-mL column. Also, MICP by WJ-2 was evaluated for its potential to counteract Sr contamination in column experiments using natural sand. WJ-2-induced precipitation led to successful sequestration of approximately 80 % of the Sr from the soluble fraction of the sand. The utility of MICP in bioremediation was further confirmed through X-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectrometry.

Alterations in membrane phospholipid fatty acids of Gram-positive piezotolerant bacterium Sporosarcina sp. DSK25 in response to growth pressure.

Pressure is an important thermodynamic property of the ocean and the deep biosphere that affects microbial physiology and biochemistry. Here, we report on our investigation of the response of Gram-positive piezotolerant bacterium Sporosarcina sp. DSK25 to hydrostatic pressure. Strain DSK25 responded in an adaptive manner to upshifts of growth pressure and showed systematic changes in phospholipid fatty acids. As the pressure increased from 0.1 to 10 MPa (Megapascal), unsaturated fatty acids in DSK25 increased from 21.7 to 31.1% of total fatty acids, while the level of iso- and anteiso-branched fatty acids remained unchanged. At higher pressures (30, 50, and 60 MPa), the amount of unsaturated fatty acids decreased, and that of anteiso-branched fatty acids increased from 34.4 to 49.9% at the expense of iso-branched fatty acids. For the first time, two polyunsaturated fatty acids (PUFA), 18:2n-6 and 18:2n-x, with the latter having much higher abundance than the former, were identified in DSK25. The concentration of the PUFA increased with growth pressure. These results indicate the involvement of unsaturated and methyl-branched fatty acids in the modulation of bacteria membrane fluidity and function over environmentally relevant parameter (pressure). Piezotolerant bacterium Sporosarcina sp. DSK25 appears to utilize two regulatory mechanisms for adaptation to high pressure, a rapid-responding mechanism on transient scale, expressed as increased biosynthesis of monounsaturated fatty acids, and a long-term adaptation mechanism in increased synthesis of anteiso-branched and polyunsaturated fatty acids. Our results further suggest that Gram-positive piezophilic bacteria respond differently than Gram-negative bacteria in adaptation to high pressure.

Influence of temperature on the effectiveness of a biogenic carbonate surface treatment for limestone conservation.

So far, most studies on microbiologically induced carbonate precipitation for limestone conservation have been performed at temperatures optimal for the activity of the calcinogenic bacteria (i.e., 20-28 °C). Successful application in practice, however, requires adequate performance in a wide range of environmental conditions. Therefore, the aim of this study was to select microorganisms that are most suited for biodeposition at temperatures relevant for practice. In a first step, ureolytic microorganisms were screened for their growth and ureolytic activity at different temperatures (10, 20, 28, and 37 °C). Large differences in calcinogenic activity could be observed between experiments performed on agar plates and those performed in solution and in limestone. In a second step, the influence of temperature on the performance of the biodeposition treatment with different ureolytic microorganisms was evaluated, both on the consolidative and protective effect of the treatment. In contrast with the experiments on agar plates, the Sporosarcina psychrophila strains failed to produce significant amounts of calcium carbonate on limestone in conditions relevant for practice, even at 10 °C. This resulted in a poor performance of the treatment. From experiments performed on limestone prisms, it appeared that the mesophilic Bacillus sphaericus produced the highest amount of carbonate in the shortest amount of time at all temperatures tested. As a result, compared to the untreated specimens, the highest consolidative (64 % lower weight loss upon sonication) and protective effect (46 % decreased sorptivity) were observed for the treatments with this species. From this study, it appears that among all ureolytic strains tested, B. sphaericus is most suited for biodeposition applications in practice.

Inhibition of Sporosarcina pasteurii under anoxic conditions: implications for subsurface carbonate precipitation and remediation via ureolysis.

The use of Sporosarcina pasteurii to precipitate calcium carbonate in the anoxic subsurface via ureolysis has been proposed for reducing porosity and sealing fractures in rocks. Here we show that S. pasteurii is unable to grow anaerobically and that the ureolytic activity previously shown under anoxic conditions is a consequence of the urease enzyme already present in the cells of the aerobically grown inoculum. The implications are discussed, suggesting that de novo synthesis of urease under anoxic conditions is not possible and that ureolysis may decline over time without repeated injection of S. pasteurii as the urease enzyme degrades and/or becomes inhibited. Augmentation with a different ureolytic species that is able to grow anaerobically or stimulation of natural communities may be preferable for carbonate precipitation over the long term.

Biomineralization based remediation of As(III) contaminated soil by Sporosarcina ginsengisoli.

Arsenic is a highly toxic metalloid and has posed high risk to the environment. As(III) is highly mobile in soil and leached easily into groundwater. The current remediation techniques are not sufficient to immobilize this toxic element. In the present study, an As(III) tolerant bacterium Sporosarcina ginsengisoli CR5 was isolated from As contaminated soil of Urumqi, China. We investigated the role of microbial calcite precipitated by this bacterium to remediate soil contaminated with As(III). The bacterium was able to grow at high As(III) concentration of 50mM. In order to obtain arsenic distribution pattern, five stage soil sequential extraction was carried out. Arsenic mobility was found to significantly decrease in the exchangeable fraction of soil and subsequently the arsenic concentration was markedly increased in carbonated fraction after bioremediation. Microbially induced calcite precipitation (MICP) process in bioremediation was further confirmed by ATR-FTIR and XRD analyses. XRD spectra showed presence of various biomineralization products such as calcite, gwihabaite, aragonite and vaterite in bioremediated soil samples. The results from this study have implications that MICP based bioremediation by S. ginsengisoli is a viable, environmental friendly technology for remediation of the arsenic contaminated sites.

Effects of environmental factors on microbial induced calcium carbonate precipitation.

AIMS: To gain an understanding of the environmental factors that affect the growth of the bacterium Sporosarcina pasteurii, the metabolism of the bacterium and the calcium carbonate precipitation induced by this bacterium to optimally implement the biological treatment process, microbial induced calcium carbonate precipitation (MICP), in situ. METHODS AND RESULTS: Soil column and batch tests were used to assess the effect of likely subsurface environmental factors on the MICP treatment process. Microbial growth and mineral precipitation were evaluated in freshwater and seawater. Environmental conditions that may influence the ureolytic activity of the bacteria, such as ammonium concentration and oxygen availability, as well as the ureolytic activities of viable and lysed cells were assessed. Treatment formulation and injection rate, as well as soil particle characteristics are other factors that were evaluated for impact on uniform induction of cementation within the soils. CONCLUSIONS: The results of the study presented herein indicate that the biological treatment process is equally robust over a wide range of soil types, concentrations of ammonium chloride and salinities ranging from distilled water to full seawater; on the time scale of an hour, it is not diminished by the absence of oxygen or lysis of cells containing the urease enzyme. SIGNIFICANCE AND IMPACT OF STUDY: This study advances the biological treatment process MICP towards field implementation by addressing key environmental hurdles faced with during the upscaling process.