The thrust of this proposed research is to enhance the performance of concrete using novel microbial products of genetically engineered microorganisms (GEMs). The prime microbial product to be studied is the extracellular polymeric substance (EPS) that promotes microbes to adhere to various types of the surface structures. Selective cementation properties of the microbial organic polymer will be compared with those of the microbiologically induced inorganic calcite that was introduced from our previous studies. In this study, we propose an ambitious plan to develop GEMs that harbor and express genes responsible for the biopolymer production as well as calcite precipitation simultaneously. With the reduced budget, the scope of this research has been revised (1) to develop GEMs that produce various types of biosealant for concrete remediation and (2) to apply these genetically engineered microbial products in concrete in a reduced scale.
The intellectual merit of the proposed study is to introduce new, advanced and innovative approaches in microbial concrete enhancement, intending not to merely continue the previous research, rather elevating this concept to the next level. The most significant aspects of the proposed research are the identification of alternative biological products that can be used for concrete remediation effectively without any adverse impact to environments and the use of cutting-edge molecular DNA and immobilization technology in concrete remediation, utilizing preliminary findings from on-going research on recombinant microbial urease. Further, this proposed research scheme includes the development of a method that can preserve microbial sealing material for an extended period of time.
Through previous NSF funded projects (CMS-9802127 and INT-0002608), Dr. Bang (Environmental Microbiologist) and Dr. Ramakrishnan (Civil/Concrete Engineer) at the South Dakota School of Mines and Technology (SDSM&T) have established close interdisciplinary research collaboration. The collaborative research efforts between the PIs have emphasized engineering application of basic concepts of microbiologically induced calcite precipitation, which is the underlying cornerstone of this proposal. In addition, through the current funding from the NSF/INT program, our research collaboration has expanded to include an Australian research team, Dr. J.R. Warmington (School of Biomedical Sciences) and Dr. B.V. Rangan (School of Civil Engineering) of the Curtin University of Technology, Perth, Australia. This international collaboration between SDSM&T and Australian research teams has provided an opportunity to complement two campuses' expertise and laid major groundwork for this proposal. The broader impacts of the proposed activity emphasize the following two aspects: (1) REU supplementary funding will be requested to recruit underrepresented minority students on campus and from adjacent tribal colleges in South Dakota. These undergraduate students will actively participate in the project, assisting graduate students' research and further developing their own independent research topics. Students will be encouraged to participate in hands-on experiments, analysis and assembly of data, presentation at conferences, and preparation of scientific papers. Our interdisciplinary research efforts will also provide unique opportunities to undergraduate and graduate students, through which students will gain significant research experience and develop critical thinking skills. (2) As for potential applications beyond concrete reinforcement, these environmentally innocuous biological products may be utilized with slight modification as sealing or caulking agents for the gaps in building structures, bioremediation means to confine contaminated aquifers or subsurface soils through selective cementation, and possibly dust control for surface soils. Therefore, the importance and significance of the proposed novel approaches span not only the feasibility of application in concrete enhancement but also further applicability of the technique in other areas of remediation.