This is the 12th year that BIT-China has participated in the iGEM competition, and we are well aware of how much of a legacy iGEM is. Our team leader this year, Zhao Xuanye, said, 'Some iGEM projects are like samples in hippop music, where generations of young iGEMers find out old parts or technology left behind by their predecessors in the Registry of PARTS, and give it a whole new life or stage.'

The inspiration for BIT-China's project this year came not only from literature research but also from learning from previous projects. Their contributions provided us with ideas, for which we express our gratitude. Moreover, we hope that our contributions can also help future iGEM teams.

Parts Contribution

Yeast surface display is a highly valuable technology with wide applications in antibody engineering, enzyme engineering, protein engineering, and vaccine development. In addition, fluorescent proteins and enzymes have already been displayed on yeast surfaces as biosensors. In this year's project, we developed a brand-new yeast display system using Pichia pastoris GS115 as the chassis cell, employing the Pir system's Pir protein as the anchor protein for display. This system has been demonstrated to efficiently display proteins in our experiments. When using it, teams only need to replace the gene of the target protein. Other iGEM teams in the community can use this system for protein-directed evolution and optimization or to immobilize biorecognition elements, creating biosensors with high sensitivity and specificity. We are excited to see this system being utilized in novel designs.

Fig. Pichia Pastoris GS115 Surface Display System

Polypeptide self-assembly is a powerful technique in materials science, enabling the formation of complex nanostructures through molecular interactions. This property is particularly beneficial for biometal recovery, enhancing metal-binding capacity with efficient, high-surface-area structures.

Our project utilizes yeast surface display combined with nickel-binding peptide self-assembly to create a novel biometal recovery system. In this design, yeast cells act as "fishing boats," and the self-assembled peptides function as "nets" to capture metal ions, significantly improving capture efficiency over traditional methods.

The system demonstrates several advantages: it forms stable structures under mild conditions, allows tunable functionality through sequence modifications, and offers high surface areas for optimal interaction with metal ions. This innovative approach is expected to be applied to environmental remediation and biosensor development, paving the way for biometal recycling technologies.

We successfully expressed the highly efficient urease gene from S. pasteurii in E. coli and optimized the expression conditions, resulting in high activity. This not only provides a key enzyme for biomineralization but also offers a reference for future iGEM teams constructing other enzyme expression systems. We characterized the mineralization products using various techniques, including optical microscopy, polarized light microscopy, AFM, SEM, and EDS. The results showed that the recombinant urease could effectively convert metal ions like Li, Mn, Co, and Ni into carbonate precipitates, providing valuable insights for future iGEM teams working in the "metal recovery and recycling" field. Specific details can be found on the Parts page.

Characterization Contribution

This year, we employed new technologies in our experiments: Graphite Furnace Atomic Absorption Spectroscopy (GFAAS), High-Performance Liquid Chromatography (HPLC), Bruker Dimension XR FastScan Atomic Force Microscope (AFM), and Scanning Electron Microscopy (SEM).

These four techniques are new challenges we hadn't encountered in previous years. After continuous learning, we mastered these techniques and compiled corresponding instruction manuals. These manuals not only provide detailed technical guides and operational procedures but also cover instrument maintenance, care, and safety precautions, all of which are crucial to ensuring the success of experiments. Additionally, the manuals emphasize the importance of standardized operations, offering a series of standardized procedures that are essential for improving the reproducibility of experiments and the reliability of results. We believe that with these four manuals, future iGEM teams will be able to utilize these powerful analytical tools more effectively. Detailed content can be found on the Measurement page.

Hardware Contribution

With the promotion of intelligent recognition and automation technology, BIT-China this year advanced the integration of automation technology into the synthetic biology project. Our intelligent sorting system can classify objects based on color recognition, facilitating the next steps in operations. Teams interested in hardware in the future can download related files from the hardware page to learn more. This system can also be adapted by replacing sensors to achieve recognition based on different parameters, such as distance, pH value, etc., and additional devices can be added to carry out specific operations based on recognition feedback. Detailed content can be found on the Hardware page.

Model Contribution

This year, BIT-China chose to use the software XACS for modeling, and by simulating the results, we predicted the binding sites between proteins and metal ions. This can help future iGEM teams involved in designing metal ion-binding peptides to understand how to design for improved binding effects and performance, as well as providing important references for experimental validation.

Additionally, we compiled a database of the simulation results, including protein sequences, metal ion types, binding affinity, and selectivity, as a reference for future teams in selecting metal ion-binding gene sequences. Currently, many types of peptides capable of binding to metal ions have been discovered, but the binding mechanisms remain unclear. The structural optimization simulation results reveal the microscopic processes, which can help future iGEM teams better understand the interaction mechanisms between proteins and metal ions, providing a theoretical foundation for designing more effective proteins. We believe that our Model can provide more precise guidance for experiments.

Sustainable Development Goals Contribution

In this year's sustainability work, the concept we most want to introduce to the iGEM community is our evolving understanding of SDGs. Initially, we passively understood the concept of SDGs and our relationship with them, but this developed into considering how our project could be redesigned, future-planned, or even engineered to better achieve SDG goals—similar to the work of integrated human practices, letting the SDGs truly impact us. This year, our choices regarding carbonic anhydrase and urease, the future design of hardware recycling, and CO₂ capture and utilization in future applications all reflect our thoughts and work in this area. Although, due to time constraints and project progress, we were unable to complete a full iteration driven by SDGs, we are still very proud of this idea. In addition, based on our experience this year, we have provided future iGEMers with a methodology to understand SDGs from scratch. Our exploration of SDGs this year has brought us great joy, and we look forward to seeing more iGEM teams pursue the Sustainable Development Goals in the future.