Since our material contains biological components, it is relevant to consider whether it could directly impact human health. Our prototype development team has devised protocols in which the final product tries to mitigate this risk.

In practice this means:

1. Firstly, the biological and non-biological components are mixed together.
2. Then the mixture is packed into moulds and incubated at 25°C, through this process the biological components have time to establish themselves. Meaning mycelium can grow through the material and B. subtilis has time to biomineralise.
3. When the material had time to fully establishes itself structurally, the brick will be baked at 60-70°C for a few hours and then treated with temperatures exceeding 120°C to terminate any remaining life [2].

The heat treatment serves 3 functions:

1. By heat curing the material toughens as the hydrogel polymer chains cross link and dehydrate and tension throughout the brick cross link and also the mycelial matrix hardens.
2. B. subtilis cells should progressively die as the calcium carbonate shell around the cell surface prevents access to nutrients. Yet to mitigate risk, by baking the material the cells die from heat shock, while the material is able to maintain its structural properties.
3. Heat shock minimises the risk of contamination from other unwanted organisms.

Currently our vector contains an antibiotic selection marker for genetic stability and colony selection. We first intend to remove antibiotic requirements and utilise an auxotrophic complementation to ensure stability. Our current protocol involves curing the bricks at 120°C to ensure that all B. subtilis is killed off following mineralisation.

The biomineralization process will be taken to completion with the data on how long this will take will be conducted in future work. During the stationary phase and death phase of this process, B. subtilis will produce spores which are incredibly resistant and dormant until exposed to conditions suitable for propagation. These spores being physically crystalised into the material poses a minimal risk of environmental exposure while giving us an exciting possibility for self healing applications in the future.

• Once fully mineralised our material will be very similar to cement, with the calcium carbonate crystals insoluble to water, locking together our aggregate mix.
• Additionally, once baked we noticed mycelium gains hydrophobic properties. This is an exciting additional feature that can be explore in the future as our bricks can grow their own water-resistant coating preventing water ingress.

Long term properties of our material still need to be tested however, chemically it utilises the same hydration reaction to create calcium carbonate. Full mineralisation of concrete can take years, increasing in compressive strength over time, we expect a similar progression of our material as it is compacted

As has been highlighted during the COVID-19 pandemic, global supply chains and ‘just in time’ / ‘lean’ manufacturing can be a vulnerability to commercial operations. The team has considered the feedstocks need to produce our biomaterial, and one of the largest sources of risk has been identified as urea acquisition. Since urea is widely employed in the agricultural sector in fertilizer, its cost and availability are closely tied to the market. Recently, economic sanctions and export restrictions being placed on some key exporters of urea and fertilizer have meant that urea is currently trading at record prices [3].

Basic mitigations such as stockpiling could obviously be employed to lessen the risk of a lack of urea halting manufacture of our product. However, our team has engineered a more ingenious solution to this issue into the biological component of our product. Our cells simultaneously employ two distinct enzymatic mechanisms for biomineralization. Whilst the urease-based mechanism requires urea as an input, the mechanism which employs carbonic anhydrase does not, and could be used in isolation. Previous research, which informed our project, has created biomaterials (via biomineralization) using only the carbonic anhydrase pathway [4]. Beyond this, we have also utilised wastewater (sewage) as an input stream into our process. It serves as a source of urea and other minerals.

Our life cycle assessment has illumed our manufacturing process to be water intensive. Thus, water availability and scarcity should be considered when locating manufacturing facilities. As water scarcity is a large and growing problem in and of itself, have used wastewater (sewage) as our primary input stream. This, as aforementioned, has the added benefit of providing a source of urea.

As part of a sustainability-focused project, distribution must be considered as a source of emissions alongside its relevance as a logistical challenge. Our BioCement, as a dried product, provides a format for distribution which is preferable to BioBrick. It is both lighter and more compact, meaning that the amount of material required to create a given mass of solid can be transported with significantly fewer emissions than if the analogous mass of BioBrick were to be moved. As has been discussed above, longer term plans for manufacturing and distributing larger masses of either product incorporate future infrastructure for distributed biomanufacturing in multi-purpose bioprocessing facilities spread throughout geographies.

The main challenges in marketing our product will be negative attitudes towards genetic engineering and a lack of knowledge relating to biomanufacturing and biomaterials amongst populations. Part of our project has involved surveying consumers shopping at hardware stores across Western Europe (UK), Central Europe (Slovakia, Austria, Germany), Eastern Europe (Romania), Asia Pacific (Taiwan), and North America (USA), which has allowed us to map how public perceptions of genetic engineering and biomaterials vary based on geography (see human practices). This will allow us to target our efforts in marketing and education towards populations where it will be needed to facilitate early adoption.

Both BioBrick and BioCement have been designed to be easily used by consumers and construction companies in the same way that ready-mix cement or solid concrete is currently used. However, public awareness of the synthetic biology and bioengineering behind our product will still be needed for the product to be fruitfully employed. With this knowledge, consumers can appreciate why the product possesses the qualities it has and ideate on how the technology might be adapted for their own use cases of interest. As part of our project, we have run workshops online on the topic of programming for biology, have run a workshop on biomineralization and biomaterials in a school, and have produced educational multimedia content which has been broadcast through our social media channels as well as through platforms such as the UCL Department of Biochemical Engineering website.