Microbially induced calcite precipitation (MICP) or biocementation is a bio-mediated process that can be used to improve the engineering properties of granular soils through calcium carbonate precipitation. Although most commonly this process is accomplished using microbial urea hydrolysis, other microbial metabolic pathways can be used to enable biocementation with the potential to eliminate ammonium byproducts. Microbial organic acid oxidation presents one alternative pathway by which increases in solution carbonate species can be generated to enable calcium carbonate mineral formation. While past studies have considered the potential of this microbial pathway to enable biocementation for surficial applications, to date few studies have examined the feasibility of this pathway for subsurface applications wherein dissolved oxygen is more limited. In this study, 18 small-scale batch experiments were performed to investigate the ability of microbial organic acid oxidation to enable biocementation soil improvement. Experiments investigated the feasibility of using both acetate and citrate oxidation to mediate biocementation as well as the effect of differences in techniques used to supply dissolved oxygen, the effect of supplied growth factors, bicarbonate salt additions, and solution sampling frequency. Results suggest that aerobic oxidation of acetate and citrate can be used to enable calcium carbonate biocementation, though ensuring dissolved oxygen availability appears to be critical towards enabling this process.
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This content will become publicly available on May 30, 2025
Surface-displayed silicatein-α enzyme in bioengineered E. coli enables biocementation and silica mineralization
Biocementation is an exciting biomanufacturing alternative to common cement, which is a significant contributor of CO2greenhouse gas production. In nature biocementation processes are usually modulated via ureolytic microbes, such as
- Award ID(s):
- 1821389
- PAR ID:
- 10536718
- Publisher / Repository:
- Frontiers
- Date Published:
- Journal Name:
- Frontiers in Systems Biology
- Volume:
- 4
- ISSN:
- 2674-0702
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Bio‐mediated soil improvement technologies leverage microbial enzymatic and metabolic processes to generate minerals, gases and biopolymers that can improve soil engineering behaviours with the potential to reduce detrimental environmental impacts when compared with conventional methods. Ureolytic biocementation is perhaps the most widely researched of these processes and relies on urea hydrolysis in the presence of calcium to initiate the precipitation of calcium carbonate minerals on soil particle surfaces and contacts, thereby improving soil behaviours. Although effective, urea hydrolysis generates aqueous ammonium by‐products that may result in undesirable environmental and human health impacts, if left unaddressed. Recent studies have shown the potential of rinse solution injections to effectively remove generated ammonium following biocementation through both advective flow and the removal of sorbed ammonium from soil surfaces; however, critical gaps remain in our understanding of the effect of rinse solution composition and injection strategies on ammonium removal efficacy. In this study, 16 soil column experiments were performed to investigate the effect of rinse solution cation types, cation concentrations, applied injection sequences and biocementation treatment variations on the removal of ammonium from a biocemented poorly graded sand. All columns receiving cation‐enriched rinse solutions achieved greater than 98% aqueous, 65% sorbed and 95% total ammonium removal after injecting 12 pore volumes, with no detectable impacts on cementation integrity. Cation‐enriched solutions specifically enhanced sorbed ammonium removal and achieved sorbed ammonium concentrations up to 2 orders of magnitude less than those observed in columns rinsed with deionized water alone. Columns receiving K+‐based rinse solutions and 12 daily 1‐PV rinse injections also achieved greater total ammonium removal when compared with comparable columns receiving rinse solutions containing other cations and continuous 12‐PV rinse injections.
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Abstract Bacterial cellulose (BC) has excellent material properties and can be produced sustainably through simple bacterial culture, but BC‐producing bacteria lack the extensive genetic toolkits of model organisms such as
Escherichia coli (E. coli ). Here, a simple approach is reported for producing highly programmable BC materials through incorporation of engineeredE. coli . The acetic acid bacteriumGluconacetobacter hansenii is cocultured with engineeredE. coli in droplets of glucose‐rich media to produce robust cellulose capsules, which are then colonized by theE. coli upon transfer to selective lysogeny broth media. It is shown that the encapsulatedE. coli can produce engineered protein nanofibers within the cellulose matrix, yielding hybrid capsules capable of sequestering specific biomolecules from the environment and enzymatic catalysis. Furthermore, capsules are produced which can alter their own bulk physical properties through enzyme‐induced biomineralization. This novel system uses a simple fabrication process, based on the autonomous activity of two bacteria, to significantly expand the functionality of BC‐based living materials. -
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Abstract Regulation of the heat shock response (HSR) is essential in all living systems. In
E. coli , the HSR is regulated by an alternative σ factor, σ32, which is encoded by therpoH gene. The mRNA ofrpoH adopts a complex secondary structure that is critical for the proper translation of the σ32protein. At low temperatures, therpoH gene transcript forms a highly structured mRNA containing several three‐way junctions, including a rare perfectly paired three‐way junction (3WJ). This complex secondary structure serves as a primitive but highly effective strategy for the thermal control of gene expression. In this work, the first small‐molecule modulators of theE. coli σ32mRNA temperature sensor are reported. -
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Cell-free protein expression is increasingly becoming popular for biotechnology, biomedical and research applications. Among cell-free systems, the most popular one is based on
Escherichia coli (E .coli ). Endogenous nucleases inE .coli cell-free transcription-translation (TXTL) degrade the free ends of DNA, resulting in inefficient protein expression from linear DNA templates. RecBCD is a nuclease complex that plays a major role in nuclease activity inE .coli , with the RecB subunit possessing the actual nuclease activity. We created aRecB knockout of anE .coli strain optimized for cell-free expression. We named this new strain Akaby. We demonstrated that Akaby TXTL successfully reduced linear DNA degradations, rescuing the protein expression efficiency from the linear DNA templates. The practicality of Akaby for TXTL is an efficient, simple alternative for linear template expression in cell-free reactions. We also use this work as a model protocol for modifying the TXTL sourceE .coli strain, enabling the creation of TXTL systems with other custom modifications.
