Overview ​

Lychee, a fruit of high cultural and economic importance in Southern China, suffers from a very short shelf life. Within just a few days after harvest,fruits rapidly lose moisture, deplete nutrients, brown, and decay, leading to losses of up to 30–40% of production. Current solutions such as cold storage or chemical treatment are either costly or raise safety concerns. Our HKUST(GZ) iGEM 2025 team proposes an integrated synthetic-biology strategy to extend lychee shelf life. We designed:

Melatonin regulation to slow respiration, prevent oxidative browning, and enhance fruit immunity.

Microbial wax coating to form a natural protective barrier that retains moisture and resists pathogens.

To support this, our dry-lab tools include AI-driven genome design (BactaGenome, SynbioMCP), a lychee dataset and recognition app, and aprecision-spraying drone system. Together, these modules form a comprehensive, safe, and scalable approach to lychee preservation that integrates biology,computation, and engineering.

Problem Statement ​

Lychee is among the most perishable tropical fruits. Its thin peel, high moisture content, and rapid metabolism make it extremely vulnerable after harvest.Within just 2–3 days at room temperature, lychees begin to lose water, suffer oxidative browning, and become prone to fungal decay. Even under coldstorage, shelf life rarely exceeds 14–21 days, and quality loss continues.

Existing preservation methods are far from ideal. Cold chain systems require high infrastructure costs and are often unavailable in rural productionareas. Chemical preservatives can slow browning but raise food safety and consumer acceptance concerns. Conventional handling practices—such assulfur fumigation—are increasingly restricted due to health and environmental risks. As a result, postharvest losses remain high: studies report 20–40% ofharvested lychees are wasted before reaching consumers .

These limitations have severe consequences. Farmers lose income due to reduced marketability, distributors face high logistics costs, and consumers oftenencounter poor-quality fruits. Most importantly, the short shelf life restricts lychee exports and limits the fruit’s cultural and economic value on aglobal scale.

To overcome these challenges, new strategies must combine safety, effectiveness, and scalability—preserving lychees in a way that benefits producers,consumers, and the environment alike.

Solution ​

To overcome this, we propose a preservation method combining a wax membrane and exogenous melatonin. The wax membrane works primarily by reducing water loss(thus decreasing weight loss) and preventing microbial infection , while the melatonin acts as a potent antioxidant , anti-aging , and immune-boosting agent . This combined approach is designed to enhance the fruit’s natural defenses, extend shelf life, and maintain its freshness.

Compared with directly sprayed melatonin and wax, the advantages of melatonin and wax produced by Bacillus subtilis in our study are reflected in the following two aspects:

• It enables the bacteria to continuously produce melatonin, while simultaneously reducing the cost of melatonin synthesis.

• The micro-wax can cover the cracks on lychee fruits without affecting their appearance, thereby achieving the preservation of lychee.

  

(For details, please refer to the circuit design.)

Innovation ​

Our project introduces several innovations that go beyond conventional lychee preservation methods. Instead of relying solely on cold storage or chemicalpreservatives, we integrate synthetic biology, computational modeling, and engineering tools into a single pipeline:

Biological Innovation ​

Melatonin regulation: Unlike chemical treatments, melatonin is a naturally occurring molecule that slows respiration, delays browning, and enhancesimmunity without introducing harmful residues.

Microbial wax coating: By engineering bacteria to produce edible wax esters, we create a bio-derived protective layer. This offers a sustainablealternative to synthetic coatings and can be applied directly in the supply chain.

Computational & Engineering Innovation ​

BactaGenome: An AI-driven platform for bacterial genome design, adapted to handle 100 kbp DNA sequences at single-base resolution. It accelerates promoter/RBS optimization and pathway design for our wax and melatonin modules.

SynbioMCP: A natural-language AI agent that allows non-computational team members to design and analyze biological systems, democratizing access todry-lab tools.

Lychee dataset & recognition app: A comprehensive digital resource that supports both scientific research and consumer education through a WeChat mini-program.

Drone-based spraying system: A precision agriculture tool that combines real-time computer vision with automated treatment application, making our strategy scalable in the field.

Human Practices Innovation ​

We engaged diverse stakeholders—from farmers to consumers—to ensure our design prioritizes safety, accessibility, and cultural relevance.

Inclusive educational activities, such as the Lychee Preservation Science Class for students with intellectual disability, broaden the social impact of synthetic biology.

We moved beyond traditional lectures, designing activities like workshops, art submissions, interactive games, and stream media that encourage active participation and creativity.

In summary, our innovation lies not in a single technique but in the integration of biological regulation, real-time sensing, computational design, and scalable deployment. This holistic approach redefines lychee preservation as a safe, sustainable, and socially inclusive model for synthetic biology applications in agriculture.

Expected Impact ​

Agricultural & Economic ​

Reduced postharvest loss: By extending lychee shelf life from only a few days to several weeks, we can recover a large portion of the 20–40% of fruits currently wasted each season.

Increased farmer income: Longer shelf life improves marketability and allows access to distant markets, directly benefiting growers and distributors.

Export potential: Preserved quality supports international trade, unlocking new economic opportunities for the lychee industry.

Scientific & Technological ​

Synthetic biology in agriculture: Demonstrates how genetic circuits (melatonin regulation, microbial wax synthesis) can be applied to real-world crop preservation.

Computational empowerment: Our AI platforms (BactaGenome, SynbioMCP) showcase how machine learning can accelerate design and make dry-lab tools accessible to people unfamiliar with computational tools and programming.

Scalability: The drone system provides a path toward field-level deployment of synthetic-biology solutions.

Social & Educational ​

Food safety and sustainability: By replacing chemical treatments with bio-derived solutions, our project promotes healthier and environmentally friendly preservation practices.

Education and inclusivity: Outreach activities foster public understanding of synthetic biology and create accessible learning opportunities, from highschool students to community members.

Conclusion ​

In the long run, our project envisions a new paradigm of fruit preservation that integrates biology, computation, and social responsibility — not only for lychees, but also as a model for other perishable crops.

References ​