PROJECT DESIGN
Introduction
BCoated is developing a modular seed coating platform designed to address multiple seed-related challenges within a single system. Our approach combines the unique properties of bacterial cellulose (BC) with tools from synthetic biology to create a versatile and adaptable material. The project is structured into three phases: (1) functionalisation of BC through introduction of heterologous genes or overexpression of native ones, regulated by inducible promoters, alongside the use of proteins including enzymes to directly modify or embed within the cellulose matrix, to tailor BCs properties; (2) production platform of BC by co-culturing Komagataeibacter sucrofermentans and Saccharomyces cerevisiae to optimise BC yield, extend the toolbox, and increase the substrate range; and (3) seed coating and application where the performance of BC as coating material is assessed in different applications (Figure 1). This page outlines the overall concept, not only describing how the final product is envisioned to be produced, but also how human practices and entrepreneurship guide its development into a potential solution for agricultural problems.
Functionalisation
The goal of the functionalisation phase is to develop BC into a modular polymer that can serve as a seed coating. One of our stakeholders noted that while current seed coatings can improve yield, their potential remains underused due to reliance on harsh chemicals and limited modularity. Currently, no single coating material can address all seed-related challenges. Hence future research was highly encouraged to focus on developing custom coatings tailored to meet the unique needs of different seeds1. These insights, together with our own values guided us to design a flexible platform for modular seed coatings derived from BC, providing a one-pot solution designed to help seeds overcome their challenges and ultimately help farmers in tackling crop-related problems.
Learn more about our integrated human practices
As a first step, we investigated the use of cellulose-binding domains (CBDs) as anchors to attach proteins to the BC matrix. The attachment of proteins is another key feature of seed coatings, particularly in light of advances in modern coating technologies1. Thus, we enable this attachment onto our BC matrix, but also offer an alternative to chemicals in seed coatings by adding proteins. Such attachment of proteins allow for precise delivery of nutrients, growth stimulants, and protectants directly to the germinating seed, increasing both efficiency and effectiveness2.
We then focused on tuning three key properties of BC, selected for their critical roles in effective seed coatings:
WHC: This can be adjusted as BC is naturally hydrophilic. This is done to modulate hydration, enabling BC to control seed hydration and potentially delaying or enhancing germination.
Biodegradability: This determines the release dynamics by influencing how quickly the BC matrix breaks down.
Porosity: This can be fine-tuned to enable the attachment and controlled release of beneficial compounds.
Using synthetic biology, we engineered S. cerevisiae to secrete enzymes containing CBDs, enabling the attachment of proteins to the BC matrix. We also engineered K. sucrofermentans to tune the properties of BC by introducing heterologous genes to increase biodegradability and/or porosity, which we made possible by exploring different electroporation protocols. We even tested out and succeeded in developing a novel conjugation method to which to our knowledge has not been tried before.
To demonstrate the modularity of our system, we tested a new inducible promoter with a low-cost inducer in K. sucrofermentans. These promoters act like a ‘volume control’ allowing us to fine-tune gene expression, thereby adjusting the degree of degradability, porosity, or potentially other properties in the future, resulting in a truly customisable polymer.
Beyond synthetic biology, we used an enzymatic-based approach, as an alternative to traditional chemistry, which focused on tuning WHC. We used the enzymes laccase and lipases, under gentler and eco-friendlier conditions which allowed us to modify the surface chemistry of BC and in turn affects its WHC. A detailed overview of each phase can be found in wet lab overview page.
Production platform
Our innovation lies within BC, a material whose properties we can fine-tune to create seed coatings and address a variety of agricultural issues. However, to unlock its full potential, we first develop a production platform. This platform will produce BC variants, but it does more. Not only does it create further functionalisation possibilities, it also increases the yield of BC production, and it broadens the range of substrates that BC can be produced from, creating opportunities for circular business and much more.
We start with K. sucrofermentans, a bacterium with high BC production recommended by Prof. Dr. Tom Ellis from Imperial College London (ICL), who we talked to because of his extensive experience in BC cultivation. As mentioned previously, we introduced yeast, S. cerevisiae, to open more doors for our production platform. The system operates as a microbial consortium where both species depend on each other through cross-feeding. Each organism produces metabolites that are essential for the survival of the other, to promote population balance and prevent them from outcompeting each other.
A method known to increase BC production, involves supplementing the culture medium with a controlled concentration of ethanol. Rather than relying on external ethanol addition, we take advantage of the consortium by engineering yeast, S. cerevisiae, to produce a controlled level of ethanol via a synthetic genetic circuit. This circuit halts ethanol production by inhibiting the yeast metabolism once concentrations reach the optimal value of 1% (v/v)3. After K. sucrofermentans consumes the ethanol, yeast production resumes, creating a self-regulating, more cost-efficient production loop over the long term.
To streamline development and reduce lab trial-and-error, we start by employing an ordinary-differential-equation (ODE) based mathematical model for both, the consortium and to develop the ethanol circuit.
The first model simulates population dynamics and metabolite exchange between the two consortium members.
The second model simulates the behaviours of the synthetic genetic circuit model for ethanol secretion in S. cerevisiae.
These models can accelerate the design-build-test-learn (DBTL) cycle and cut Research and Development costs, aligning with entrepreneurial goals of speeding up market readiness.
Learn more about our entrepreneurship
Seed coatings & applications
The final phase of our project demonstrates the potential and modularity of our seed coatings made from functionalised BC to address critical agricultural challenges. We outline the methods used to apply these coatings and present two application-focused cases:
Controlled delivery of pesticides: As BC can carry functional proteins fused with suitable CBDs, this is ideal for seed coating applications. In this instance, we incorporate Cry3Aa, a protein toxin that targets mealworms, into the BC used for coating. This provides a more precise pest control without relying on synthetic chemical treatments.
Parasitic weed suppression: Since BC’s porosity and biodegradability are tunable, we can also control the release of embedded compounds. Here, we use compounds that have been shown to tackle Striga hermonthica (Witchweed), a parasitic plant responsible for substantial crop losses across sub-Saharan Africa.
Altogether, our project is designed around an optimised, modular production platform for producing functionalised BC, specifically for use in seed coatings tailored to customer requirements. We offer a more sustainable alternative to traditional seed coatings containing microplastics. By engaging with stakeholders across science, agriculture, industry, and regulation, we’ve integrated their inputs to shape our project and ensure relevance. Ultimately, BCoated represents not only a synthetic biology innovation but also an entrepreneurial solution to challenges faced in agriculture.