Description


Background & Inpiration
Local Observations: Environmental Impact on Food Safety


Most of our team members are from Guangzhou, China. Guangzhou is known for its sweltering climate, with temperatures soaring up to 42 degrees Celsius annually. Such extreme heat conditions accelerate the spoilage of perishable foods, posing significant health risks. Reports indicate that numerous individuals annually are affected by foodborne illnesses due to the consumption of spoiled foods [1].


Milk Spoilage Challenges During Summer


Most of our team members are from Guangzhou, China. Guangzhou is known for its sweltering climate, with temperatures soaring up to 42 degrees Celsius annually. Such extreme heat conditions accelerate the spoilage of perishable foods, posing significant health risks. Reports indicate that numerous individuals annually are affected by foodborne illnesses due to the consumption of spoiled foods [1].


Economic Considerations and Health Implications


The elderly, especially in China, often consume milk close to or past its expiration date due to economical habits [4]. Consequently, there is a pressing need for a detection solution that is both simple and sensitive, facilitating the identification of spoiled milk, thereby mitigating health risks associated with its consumption.


Research & Design
Scientific Exploration of Spoilage Indicators


Research focusing on the differences between spoiled and fresh milk revealed that AHL-mediated quorum sensing plays a crucial role in the spoilage process. AHLs (N-acyl homoserine lactones) serve as bacterial signaling molecules that regulate metabolic activities during spoilage. As bacterial populations reach specific thresholds, AHL concentrations increase, activating genes that produce enzymes and toxins. These biochemical agents decompose food's essential components, leading to changes in taste, color, and overall quality.

In response to these findings, a high-throughput screening system was developed, incorporating a plate reader for output measurements. Our team designed standardized plasmid templates and experimented with various promoter+RBS combinations to find the most effective biosensors for spoiled milk detection. This led to the creation of a comprehensive promoter+RBS plasmid library, providing valuable resources for future research and application in synthetic biology. [5-8]

Engineering DBTL: High-Throughput Screening and Sensitivity Enhancement in Quorum Sensing Systems

  • Design: Designed a plasmid that integrates high-throughput screening with quorum sensing.
  • Build: Constructed the plasmid.
  • Test: Conducted high-throughput screening tests, evaluated milk spoilage signals, and established the relationship between milk spoilage and fluorescence values.
  • Learn: Identified that quorum sensing operates at concentration thresholds, which were crucial for the detection process.


    • We established a high-throughput screening mechanism and successfully identified a more sensitive quorum sensing system. Through this system, we were able to detect milk spoilage effectively.

    Plasmid diagram
    Fig. 1 (a) Schematic map of Transcriptional unit 1 : utilizes a strong promoter, J23119, to initiate the transcription and translation of LuxR. (b) The LuxR bound with the signal molecule will reduce the binding efficiency with Plux (Transcriptional 2), thereby initiating the transcription and translation downstream of Plux

    Value

    Responsible and Good for the world
  • Stakeholder Level: Through communication with stakeholders in the industry chain, we confirmed the practical significance of our project and clarified that our spoilage detection system prioritizes simplicity, ease of use, and sensitivity.
  • Experimental Observations and Expert Consultation: We observed limitations in the quorum sensing mechanism during experiments, sought advice from relevant experts, and received several recommendations. Additionally, we have developed various quorum sensing plasmids and hope to further explore this issue in the future.


    • Outlook

    Future Applications and Expansion The developed quorum sensing plasmid combinations were tested under various conditions to establish a reliable correlation between fluorescence and milk spoilage. Looking forward, the team plans to develop a home testing kit that could be applied not only to milk but also to other food items that are difficult to assess visually or sensorially. This innovation has the potential to significantly enhance food safety practices, particularly benefiting the elderly and other vulnerable groups.


    References

    [1] Martinović, T., Andjelković, U., Gajdošik, M. Š., Rešetar, D. and Josić, D. (2016). Foodborne pathogens and their toxins. Journal of Proteomics, 147, pp. 226-235. doi:10.1016/j.jprot.2016.04.029.

    [2] Liang, L., Wang, P., Zhao, X., He, L., Qu, T. and Chen, Y. (2022). Single-molecule real-time sequencing reveals differences in bacterial diversity in raw milk in different regions and seasons in China. Journal of Dairy Science, 105(7), pp. 5669-5684. doi:10.3168/jds.2021-21445.

    [3] Beijing Municipal Health Commission. (2016). How elderly people should scientifically drink milk. Beijing Municipal Health Commission Website. (Accessed: 20 July 2016).

    [4] Shenzhen Municipal Market and Quality Supervision Commission. (2018). Leftovers pose risks, elderly friends should not be “frugal.” Shenzhen Municipal Market and Quality Supervision Commission Website. (Accessed: 10 May 2018).

    [5] https://2015.igem.org/Team:IIT_Kharagpur/Project

    [6] https://2016.igem.org/Team:Tokyo_Tech/AHL_Assay/AHL_Reporter_Assay

    [7] https://2019.igem.org/Team:Michigan/Project

    [8] https://2021.igem.org/Team:GCGS_China/Description