This SusCheM award by the Biomaterials program in the Division of Materials Research to Harvard University is part of a broad effort to "domesticate" bacterial biofilms for the extraction of rare earth metals and materials. Biofilms are communities of bacterial cells living inside a self-generated biopolymer matrix. This project aims to genetic engineer a non-pathogenic laboratory strain of E. coli to produce altered forms of this biopolymer matrix that have beneficial functions. Specifically, biofilms will be modified the surfaces of proteins with metal binding capabilities. This modification will allow the biofilms to selectively bind to rare earth elements. Rare earths are essential for a variety of cutting edge technologies, including smartphone displays, electric vehicles, and wind turbines. As such, their availability is critical to technological innovation and resource independence in the United States. Despite this, more than 90% of the world's rare earth metals are mined and extracted outside United States because of the lack of environmental and sustainable technologies. The engineered biofilms research proposed aims to develop cheaper, sustainable, green and environment-friendly technologies to extract rare earth metals in USA. Integrated with the research plan will be an intensive student trainings program that will incorporate new teaching initiatives in the fields of biomaterials and bioengineering, and recruiting and mentorship of several graduate and undergraduate students with a focus on women and underrepresented minority students. Undergraduate students will be exposed to STEM topics with a focus on genetic engineering through established internship programs in the Campus. Coordination of outreach activities with local high schools to stimulate interest in STEM education is also part of this project.
The overall goal of this SusCheM project is to develop a platform for genetically engineering bacterial biofilms that can serve as scalable materials with programmable, non-natural functions. With this award, the Principal Investigator will study the genetic modification and characterization of the proteinaceous mesh-like surface coating present in biofilms secreted by bacteria. This proteinaceous surface coating called 'curli' contains structural proteins, which self-assemble into an encapsulating network of amyloid fibers in the biofilm. This research involves genetic fusion of peptide motifs to the 'curli' proteins such that the fused peptides are on the surface of the amyloid fibers in the biofilm. These modified 'curli' proteins will be studied for structural and functional properties with a focus on specific metal binding capabilities. The peptide modified biofilms will be produced, and their ability to form extracellular amyloids networks will be characterized as a function of peptide linker length. A plate-based screening strategy will be used to evaluate the composition and metal binding properties of the engineered biofilms and identify those that can selectively and efficiently enrich rare earth elements. The system will also be integrated in a laboratory scale continuous flow separation apparatus to evaluate its potential in an industrially relevant model. Ultimately, the results of this investigation will facilitate the development of a wide range of biofilm-based materials using renewable sources. The research will be integrated with a cross-disciplinary mentoring plan in which graduate and undergraduate students will be trained in subfields of molecular biology, materials science, and chemical/biological engineering.
