Every harvest begins with a seed. Farmers depend on seeds to support their families and feed communities. However, each crop and location is vulnerable to its unique abiotic stressors (drought, UV, heat, flooding) and biotic stressors (pests, weeds, pathogens). Ensuring reliable germination and yield is a constant challenge.

Both anonymous arable farmer and Egge Jan Hommes commonly use coated seeds. They explain that they use a different coating for each crop, as each crop comes with its own struggles. Sugar beets, for example, are pelleted to change the shape of the seeds and simplify sowing. The coating also attracts moisture to improve germination in dry times. Egge Jan Hommes also uses seeds coated with pesticides. The kind of pesticide is different for each crop, with insecticides for some crops and fungicides for others, depending on the need. An anonymous farmer is also aware of pesticide coatings, which he used to use for sugar beet and wheat. However, since neonicotinoids are banned from seed coatings in new regulations, not all seeds have a suitable coating.

In the Netherlands, seed coatings are commonly used to standardise germination and make seeds more resilient. Studies show that coatings can increase crop yields by 20–50%². They also improve handling, sowing efficiency, and early plant establishment³, making them valuable to farmers, distributors, and, of course, to communities. The benefit of coatings is that they help the plant during germination and initial growth, which results in a stronger plant later on.

“In my view, it is useful to use seed coatings, because that way you can ensure a good start and prevent a whole range of problems later on. The start of a crop is very important, so a seed coating helps enormously to give the crop a good start, allowing you to quickly get a strong plant […]”

However, today’s seed coatings have some major drawbacks:

• Over 55% are synthetic; they are made with materials such as polyacrylamide (PAM) or polyacrylic acid (PAA), contributing to microplastic pollution. This microplastic pollution accounts for ~10% of all microplastics released into the environment⁴.
• Some biodegradable alternatives exist, but mainly rely on harsh chemicals during production, and are inflexible in applying to different circumstances.

Not all farmers (anonymous arable farmer) are aware that seed coatings contain microplastics. After learning about the problem, he expressed that he would change to a more sustainable alternative if possible. Therefore, we noticed this gap in the market: there is a demand for sustainably produced biodegradable seed coatings, but there is a limited supply. We decided to commit to designing improved coatings with SynBio. Based on this market gap, we also decided to pursue the entrepreneurial route for our iGEM project.

Recognising both the benefits and current limitations of seed coatings, we investigated what future innovations should look like. From the farmers, we learned how every seed needs a customised coating, indicating the need for a modular coating material. A recent study confirmed this, highlighting that coatings must become modular and applicable to various local conditions while remaining sustainable—a principle that inspired our project design⁵.

We engaged with experts in agriculture to identify methods of designing our coatings to be flexible for different use cases. We considered incorporating microbes or different active compounds into the BC for different applications.

Dr. Desalegn W. Etalo from WUR Translational Phytopathology warned us that microbial inoculants can disrupt soil communities, either being rejected by the local community or outcompeting native microbes. Instead, he suggested using precursor molecules to “fish” for beneficial microbes.

This led us to Prof. Dr. Jonne Rodenburg from the chair group Weed Ecology at WUR. He confirmed the potential of incorporating a precursor that mitigates against disastrous parasitic weeds, preventing crop damage. This became our first proof-of-concept use case: demonstrating parasite control through modular BC coatings. This can provide a simple solution for farmers worldwide. Currently, these farmers have to rely on labour-intensive methods that can do nothing more than mitigate losses.

Based on their input, we needed to find a modular material suitable to encapsulate active compounds. Ideally, the material would be tunable such that it can release the compound faster or slower depending on the farmer’s wishes.

Traditionally, seed coatings have relied on petroleum-based binders (adhesives, or “seed stickers”). This is a practice soon to be outlawed, as we found out from our stakeholders in the seed sector. Our consultation with Amalia Kafka from Euroseeds highlighted the urgency of this change, due to the upcoming EU microplastics restrictions under the EU chemical legislation REACH:

• By 2028: deliberately added microplastics will be restricted in agricultural products, including seed treatments.
• By 2031: the restriction will extend to all plant protection products and treated seeds.

In relation to this, some chemical pesticides have already been banned. Anonymous arable farmer mentioned that the ban on neonicotinoids now forces him to spray against pests, instead of coatings that included these pesticides. This costs more time, and spraying is worse in performance, according to him. Not to mention that spraying exposes him to these toxic fumes.

This made us realise that biodegradability of the coating material and incorporating bio-based active compounds (rather than chemical) is not only a market preference, but a soon-to-be legal requirement that has already begun affecting farmers.

In meetings with Maroushka Blahetek (Carapace Biopolymers), we were advised to search for opportunities to replace agrochemical active compounds with biologicals, ideally using one biodegradable material/polymer compatible with many applications. This confirmed what we had learned from literature: the importance of modularity⁵.

Additionally, all the consultations we had with stakeholders knowledgeable of the seed sector—namely, ecological agriculture academic Dr. Bert Smit , Maroushka Blahetek from Carapace Biopolymers, CEO of Seedforward Dr. Jacob P. Rohn , Amalia Kafka from Euroseeds, and others—highlighted the same non-negotiables for an improved seed coating. These included practical factors, such as long storage durability, consistency in colour and high yields; and factors impacting farmer health, such as dust control.

Accordingly, we began searching for a biodegradable matrix that could carry different active compounds while remaining low-cost. Early brainstorming sessions also led us to consider whether binding proteins to the matrix material could be a novel way to functionalise coatings for multiple applications.

Having identified the need for a biodegradable, modular matrix, we turned our attention to bacterial cellulose (BC). To evaluate whether BC could meet the demands of farmers, seed companies, and regulators, we reviewed literature and consulted multiple experts.

While PHA, chitosan, and alginates are biodegradable and widely studied, their use in seed coatings is often constrained by formulation challenges—such as requiring harsh solvents or acids, limited control over release kinetics, or negative effects on microbial compatibility⁶. We therefore sought a more tunable matrix for our platform. Dr. Shanmugam Thiyagajaran compared different polymers with us (PHA, chitosan, and BC) and noted that BC has reactive hydroxyl groups that could be enzymatically modified.

Prof. Dr. Tom Ellis highlighted BC’s intrinsic advantages: high tensile strength, biocompatibility, and the ability to hold 100–200× its own weight in water (very high water-holding capacity, WHC). He also noted its high surface-area-to-volume ratio, which could be exploited to attach proteins for functionalisation.

In addition to expert input, our research confirmed that cellulose already performs well in terms of dust reduction compared to many alternative coating materials. This reinforced its potential to address one of the seed industry’s most important safety concerns. Combining this information, we concluded that BC could be a suitable coating material, depending on the ease of production and functionalisation.

Production & scale-up advice: Dr. Amritpal Singh advised us on strain and bioreactor choice, recommending K. sucrofermentans for higher yields and suggesting a stacked tray bioreactor design to scale up sheet production efficiently. Inspired by these conversations, we began testing BC in the lab and brainstorming modular functionalisation approaches, such as protein binding.

Our literature survey showed that structural properties of BC—such as WHC⁷, porosity and hydrophilicity⁸, and biodegradability^{9, 10} are tunable by activating certain genes, altering operational conditions, and applying enzymatic modifications. All of these properties are interesting targets for functionalisation, as they affect germination and active-compound incorporation, which we identified as key functions of seed coatings together with farmers.

By cross-comparing stakeholder demands with expert input, we identified BC as a promising candidate: it has a sustainable production process, is highly tunable, and is biodegradable. This choice aligns not only with scientific reasoning but also with the regulatory, industrial, and customer demands our stakeholders emphasised.

Stakeholders like Jeroen van Rotterdam (Foamlab) warned us that BC is inherently sticky and difficult to handle. They also cautioned that downstream processing (DSP) could compromise the tuned properties of our coatings. In response, Dr. Zohaib Hussain suggested exploring in situ coating methods, where BC is grown directly around the seed, as well as regeneration strategies for dissolving BC in an organic solvent for easier handling. This feedback led us to successfully coat seeds in situ, though further optimisation is still required (Implementation).

An important seed coating property, according to farmers and seed companies, is the colour. Inspired by SUMATRIX Biopolymers, which boil their cellulose in coffee to colour it, we decided to try the production of BC with different colours. Attempts with red beetroot powder, spirulina and strawberry powder resulted in colourful coatings. In addition, we developed colourful proteins with a cellulose binding domain, so that the cellulose colouring can be done during the production.

For the use cases, we wanted to demonstrate that BCoated can help alleviate real problems. Through conversations with farmers and seed companies, we learned about specific agricultural challenges that our modular coatings could address. One of the pressing issues was the wireworm. It is mainly a problem in Europe, highlighted by Dr. Jacob P. Rohn from SeedForward. Wireworms cause serious crop losses by damaging the seeds and roots. Due to the legislation mentioned before, farmers have limited effective seed treatments since many chemical insecticides have been banned. Helping with the development of a bio-based insecticide and incorporating it into our seed coating could bring a direct solution to this issue.

Therefore, we functionalised bacterial cellulose by binding a bioinsecticide protein with a cellulose-binding domain (CBD). In laboratory assays, we demonstrated that this protein-functionalised coating significantly reduced wireworm feeding, providing a proof-of-concept for BC as a carrier of protective proteins. Interested in scaling up the bioinsecticide coatings, SeedForward invited us to their facility in Osnabrück to have coating trials with their equipment.

Positive Impacts

We strongly believe that our BCoated coatings will have a positive impact on human and environmental health and contribute to food security. Moreover, we will be supporting the seed sector in becoming a more inclusive market that can serve more of the pressing problems in agriculture that farmers express to be detrimental to crop yields. We plan on taking advantage of our diverse network and expanding it even more to aid in bridging the gap between market stakeholders. Our goal is to ensure that the problems, demands, and plans of these actors are all combined when implementing solutions.

Although we still need to carry out a full Life-Cycle Assessment and field trials to guarantee this as a responsible business, we propose that BCoated will reduce microplastic pollution and reduce adverse effects on human and environmental health, as BC is fully biodegradable in soil¹³. As mentioned before, this is an urgent issue, since the agricultural and horticultural sectors are responsible for ∼10% of all microplastics released into the environment¹⁴. These microplastics accumulate in the human body, with studies linking them to DNA damage, organ dysfunction, and metabolic disorders¹⁵.

Global food demand is expected to rise by 40% in the next 30 years, while population at risk of hunger is expected to change by −91% to +8% over the same period^1,. Experts believe that constructing adaptive and resilient food systems is one of the top priorities to keep up the supply. Seed coatings are already shown to increase yields by 20–50%². By creating a modular and profitable BC coating platform, our project contributes to the adaptability of seed coatings. These seed coatings will help by the establishment of strong crops (Bert Smit), strengthening food security in both the Netherlands and worldwide.

From farmers such as Egge Jan Hommes and the anonymous arable farmer, we learned that they rarely have a choice in coatings for their most pressing problems, and typically only one option is available from their supplier. From our stakeholders in the seed sector, we learned that this market is rigid and coating production often continues in traditional ways. By offering a coating platform that can be applied to different seeds and tailored for multiple functions, we aspire to create greater inclusivity and flexibility in the seed market.

Through our HP strategy, we built a diverse network that spans farmers, seed companies, cellulose manufacturers, regulators, and policymakers. This network uniquely positions us to act as a bridge between actors who often do not interact, such as farmers struggling with yield and climate unpredictability, regulators focused on safety and compliance, and companies navigating market dynamics. By continuing to expand this network and encouraging interactions, we aim to ensure that the problems, demands, and plans of all stakeholders are fused rather than neglected. In this way, BCoated does not simply deliver a technical product, but facilitates dialogue across the agricultural sector.

Negative impacts and risks

While our consultations made us confident that BCoated can deliver many positive impacts, they also made us realise that no solution is without risks. We considered and reflected on potential negative consequences that our products being adopted might have, and have thought of mitigation strategies.

BC can influence soil microbial communities¹⁶. Since these communities are critical for soil health and crop development, we plan to test multiple soil types during future field trials to assess potential unintended impacts. If certain coatings have negative effects on the soil microbiome, we aim to adjust these coatings to decrease the effect.

A second negative impact comes from the cost of seed coating. If priced as a premium product, our coatings risk becoming inaccessible for small-scale farmers with limited budgets. To prevent this, we plan to remain in close dialogue with these farmers and work with seed companies to explore special pricing models or subsidies. As feedstock choice can have a large impact on costs, we consider the feedstock choice an important factor in our production process. Establishing our product as an ecologically approved product would also help to mitigate the exclusion problem, since then the government offers subsidies. These farmers are often smaller in scale, and they are currently most excluded from seed treatment advances.

Transitioning away from synthetic polymers may additionally disrupt jobs in conventional coating industries and among their upstream suppliers. While EU regulations (e.g., the REACH microplastics ban) make this shift inevitable, it underscores the importance of planning for a just and inclusive transition.