Development of an Environmentally Benign Surfactin-based Disinfectant

Each component plays an important role in the disinfectant for targeting different areas.

As disinfection use has risen since the start of the pandemic the presence of bleach based disinfectants and quaternary ammonium compounds (QAC) have been observed in soil and wastewater. [2] Surfactants, such as QAC’s, will interact with a variety of biological components including bacteria and growths that are required to maintain a healthy ecosystem. To limit the impact from the overuse of disinfectants we must takes steps to limit the amount of cleaning products entering the environment as well as consider more eco-friendly compositions. The motivation for this project is to create an environmentally benign surfactant based disinfectant

We selected a product of bacillus subtilius, surfactin (C-15) as our primary agent. The bio-surfactant has been previously suggested to be used in oil spill remediation as it is highly biodegradable. [3] Similarly, the surfactant is near harmless to people and requires a significant amount to be ingested before any risk of acute or chronic health problems. Figure 3 below is a visual model for surfactin.

We are breaking away from tradition soaps, detergents, and disinfectants by employing bio-surfactants. Bio-surfactants are typically not used in disinfectants due to problems associated with storage and costs with cultivating the bacteria. By having our own method of producing a bio-surfactant we may overcome the associated problems and high costs of bio-surfactants in the market.

Our design meets all of our design criteria. Our formulation provides broad spectrum disinfection of hard surfaces within short exposure times. The disinfectant is easy and safe to use in residential settings. The production and life-cycle of the disinfectant is environmentally conscious and will be sustainable into the future. Our bioprocess for surfactin production also makes the disinfectant cost effective for an expanding market.

The efficacy for our design was first simulated in MATLAB using an intrinsic kinetic model for disinfection to verify our solution composition.

We were able to model the effect the initial concentration of surfactin (bulk) had on the inactivation of a virus titer. We found that at a 3% by weight composition of surfactin at least 99.9% of microbials (using an initial 1.4×10⁸ titer) were inactivated. This 99.9% inactivation falls in line with the Canadian Food and Drug Act guidelines for a general use hard surface disinfectant. Figure 4 below is the plot for the disinfection kinetics.

Furthermore, the solution was tested in a lab against a sample of E coli to test the anti-bacterial properties of the solution. Figure 5 below provides an overview of the experiment. Two disinfectants were made, one contained the the active ingredient surfactin and the other did not. Both solutions demonstrated strong anti-bacterial properties reducing the colony-forming units (CFU) from 175 CFU to 0 visible CFU.

The hydrogen peroxide and ethanol both contribute to the anti-bacterial properties of our solution. Surfactin is there to target viruses, however it will have an effect against bacteria and biofilms which can be resistant against our secondary agents. This evidence supports our secondary goal of creating a general use disinfectant that is effective against a broad range of bacteria.

Our product looks to sell 3 different products of disinfectant as units of 1L, 4L, and 120L which are sold at respective prices of $12, $34, and $950, where the 1 L and 4 L units would be sold commercially on the national level, and the 120 L would be sold internationally as a bulk product. Overall the process will be producing 2 million kg annual of the disinfectant with a total of 1.2 million units produced of which are split as 50% being 1 L, 40% being 4 L and 10% being 120 L. Assuming that all the product disinfectant would be sold we would look at an annual revenue of 20 million dollars with an annual expense of 10 million dollars meaning a net profit of 10 million per year. When evaluating the feasibility of our project a cash flow analysis was done over a 10 year period to see the longevity of the project which was found to initially require a total capital investment of 54 million dollars due to required processes to first produce the surfactin and then to produce the disinfectant solution, but the overall project was found to have a net present worth of 26 million dollars with a DCFRR of 13.7% followed by a payout period of 5 years.

As for the sensitivity of the project should still be feasible with a range of 20% decrease or increase in the 3 main factors of the fixed capital investment, expenses and revenue as the Net present worth remains positive, but larger degrees of variation are shown when revenue is changed compared to the expenses and FCI. This means that our product is both technically feasible and economically feasible.

Producing our own Surfactin became a necessity as purchasing bulk amounts of Surfactin was not an option due to it’s high costs. When designing our bioprocess, we focused on controlling variances of key parameters such as pH, temperature and dissolved oxygen levels. This was crucial to achieve optimal yields. We also modeled the growth kinetics of our process using the Monod kinetics model, this helped us to learn more about our process and estimate a batch time of 34 hours. Figure 8 below provides a visual aid for this process.

Once the bioreactor has finished its growth cycle, the harvested broth and excess foam is dissolved and passed through a membrane filtration process. The broth is passed through a series of polyether sulphone membranes of decreasing porosity, removing large cell debris in the first stage, and concentrating surfactin between the second and third stages by allowing smaller products to pass. The purified surfactin is then pumped to the mixing tanks already in a proper solution for use immediately.

The entering feed into the mixing tank is thoroughly mixed at a blending power of 2.2 kW with five 100L mixers working continuously. The mixing is done over 1 hour intervals for each new batch of feed entering which allows for thorough mixing and adequate time for the exiting solution to leave with the desired composition. This thorough mixing ensures complete miscibility and that all components are dissolved into one solution. This is then fed into a product reserve tank to then be later bottled and shipped off.