Biofilm Structures

Biofilms are the dominant form of microbial life on Earth. Inside the biofilm matrix buildup of extracellular polymeric substances (EPS) microorganisms (e.g., bacterie, fungi, algae) are embedded. Microorganisms and EPS form a three-dimensional (3D) network interacting with the surrounding fluid. Within this workpackage the complex biofilm structure will be visualized and characterized in 3D.

The 3D biofilm structure will be visualized by means of Optical Coherence Tomography (OCT), which is a more and more recognized method to non-invasively image the mesocopic biofilm structure representatively. OCT allows to visualize biofilm volumes of up to 10-by-10-by-2.8 mm³ within less than 1 minute including organic and inorganic components as well as cavities. An example of an OCT volume scan of a heterotrophic wastewater biofilm grown in a flume setup shows the figure.

This will allow us a deeper understanding of the fluid-structure interaction of biofilm systems, because the dynamics of the biofilm structure as well as its interaction with the surrounding fluid will be explored. The effects on mass transport and transfer processes will thus be elucidated. The correlation of the biofilm structure, its development, and the overall system performance – measured as power output of the microbial fuel cell (MFC) – will allow an optimized operation of the MFC.

This correlation will be used to mature the evolutionary platform by “printing” inoculation to force the “optimal” structural development with respect to development duration, costs, and performance of the MFC.

WP5 has therefore the following objectives:

  1. Set-up a cultivation experiment that allows a detailed structural characterization of the biofilm development inside a MFC
  2. Correlate biofilm structure and fluid-structure-interaction with the output power (performance) of the MFC
  3. Develop a “printing” inoculation strategy to enhance the biofilm development in new 3D printed MFCs
Recent experiments show the feasibility of OCT to image the biofilm structure directly inside the MFC without opening it.

Biofilms are created by microorganisms. Biofilms form a complex three-dimensional network, which interacts with the surrounding fluid. Due to these interactions and their metabolic activities biofilms can be ‚productive’. In EVOBLISS the production of electrical energy in microbial fuel cells (MFC) has been selected as model system to reveal the correlation between power output (‚productivity’) and biofilm structure.

The MFC design is subsequently optimized with the project partners at the Bristol Robotics Laboratory (UWE) allowing the in situ visualization of the biofilm structure by means of optical coherence tomography (OCT). Handling the OCT probe by the EVOBOT is challenging and required partly re-designing by ITU.

The biofilm structure will be characterized using structural parameters. These parameters will, together with the output power of the MFC, serve as feedback function to the EVOBOT.

The evolutionary approach of EVOBLISS, will allow the EVOBOT platform to control the imaging of the biofilm, the addition of nutritional liquids as well as the distribution of microbs based on feedback provided by the evolving system.

The biofilm coverage of the anode from the beginning, at day 10, and day 14. The scale bar is 1 mm.
The biofilm coverage of the anode from the beginning, at day 10, and day 14. The scale bar is 1 mm.
The corresponding power curve and the power curve development.
The corresponding power curve and the power curve development.
Power curve development over time.
Power curve development over time.
The development of the mean biofilm thickness over time, which we got from the image analysis of the OCT data.
The development of the mean biofilm thickness over time, which we got from the image analysis of the OCT data.

 

Technological Evolution of Synergy Between Physicochemical and Living Systems