Towards the Design of an Iterative Synbiotic Life Cycle.

Summary.

Previous observations made on the manipulation of bacteria by electrical means showed various kinetic effects with aesthetic qualities.  The study of the synbiotic mixture, i.e., a mix of probiotics and the food they need to thrive (prebiotic), led to the identification of living and non-living parts.  This work takes a step further into designing electrolytic reactions in order to achieve a cyclical dynamic behavior on the bacterial solution.  The goal was to incite and evidence recurrent living-dying processes within a Lactic Acid Bacteria (LAB) micro ecosystem.  Additionally, specific patterns, shapes, colors, and movements were obtained by modulating the components and forces that stimulated this living systems, showing a great potential for live interactive micro ecosystems design, and an interesting implementation of solid scientific foundations as catalysts for the background narrative of artistic concepts and storytelling.

Elaboration.

When observing a bacterial mix consisting of water, yogurt, salt, and the contents of a probiotic capsule (1) under the effect of electrolysis, one can easily notice various phenomena under different microscopical magnifications.  These evident phenomena such as change of bacterial flow direction and speed, oxidation and reduction processes at the electrodes, and rotation of fillers can last many hours on the microscope slide before the solution dries entirely and inactivation of bacteria takes place.  The dry state has its own peculiarities, contributing to the visual and conceptual aesthetics of the work.  However, the question here was: How can the inactivation of bacteria be accelerated and then reestablished to its living conditions and viability within ca. 30 minutes? Two approaches were analyzed:

1. Drying and wetting the mix. The drying could be accelerated by vaporizing the solution with electrolysis or hot air, or evaporation by reaching boiling temperature (100 °C at sea level).  Wetting could be done by pumping or injecting synbiotic mixture to the slide as the mix dried beyond a certain threshold.
2. Inactivation of bacteria and promoting its growth.  Bacteria can be inactivated in many ways, e.g., by applying UV light, antibiotics, an acidic or alkaline chemical reaction to lower pH levels under 4 or rising it above 9, or temperatures above 65°c.  Promoting its growth would be approached the same way as wetting the mix, because LAB growth rate is not evident within 30 minutes.

Although basic electrolysis of water with iron wire electrodes was implemented in the preceding part of this experimentation, it was further examined in detail and changed this time around.  Wetting the solution with a syringe was a new approach with interesting implications.

Electrolysis / Drying:

The key to use electrolysis in this experiment was to manage the process in specific ways.  Electrode composition, electrolyte composition, voltage and current, temperature and partition of the solution play a role on the reactions and products of the electrolytic process.  Pure distilled Water, for example, has low conductivity (18.2 mΩ at 25 °C), but tap water usually has salts (electrolytes) that allow it to conduct electricity.  In this experiment, conductivity was improved by adding table salt, sodium chloride (NaCl); thus, reducing the power loss driving the current through the solution.  Nevertheless, this reduced the electrolysis efficiency and produced new solutes, gases and materials.  Hydrogen gas (H₂ ) still formed on the cathode, but the anode got oxidized to copper ions forming a deposit of copper hidroxide Cu(OH)₂ and copper oxide Cu(OH)₂ (bluish, yellowish substances) as well as copper contamination from the erosion of the anode.  Additionally, the electric potential necessary to break water molecules is about 1.229V.  Voltages higher than that have different reactions depending on the other parameters.  A higher current flow (I) means a faster rate of reduction at the cathode and a faster rate of oxidation at he anode.  Hence, the variables in V=IR determine the rate of nano and micro bubbles in an unpartitioned solution where O^2- forms in the anode and H⁺ forms in the cathode (electrolysis of water).

After experimenting with different parameters, a stable electrolytic process was achieved using a mix of salt, water, and synbiotic (2) at 20V with tinned copper electrodes.  Electrolysis was applied for 10 minutes and then switched off to inject the mix.  A five minutes period followed to let the bacterial solution spread and afterwards the process was repeated.

Syringe Pump / Wetting:

In order to restore the living conditions for the LAB, a few drops of synbiotic solution were pumped under the slide cover with a syringe.  This was done on the cathode side to counteract the drying effects of the hydrogen gas bubbles as they advanced towards the middle of the microscope slide.

Discussion and Further Work:

The progress made on this work aiming at an iterative synbiotic life cycle, allowed a higher degree of parameter estimation (2) considering the complexities of the electrolysis of brine using copper electrodes.  Therefore, the inactivation effects of this electrochemical reaction on LAB’s physiology led to the desired living-dying rounds of repeating events.  Nevertheless, some elements of this project need a more detailed level of control while other elements raised new insights:

1. The syringe pump needs to be mechanized in order to inject solution more precisely and efficiently.  The idea behind this is to gain more control on the amount and variety of ingredients that are introduced.  The levels of pH to affect the bacteria could be better managed this way and other visual elements could be implemented as well.  A mechanism with two or more syringes is needed.
2. The live feed of the camera could be analyzed with computer vision algorithms to do a segmentation of the bacteria by means of machine learning.  This information would be used to trigger a motorized microscope x-y stage and the syringe pump automatically by dynamically determining the bacteria viability states.
3. Similarly, the microscope slide needs improvement in order to integrate circuitry that allows the modulation of the electrolysis and other variables such as temperature with more ease.
4. An autonomous micro ecosystem function, i.e., matter cycles and energy flow, needs to be developed to polish the aesthetic design of bioelectrochemical phenomena.

br41n.io hackathon project demo at the Hasso Plattner Institute / University of Potsdam for the opening reception of the ACM UIST18 conference in Berlin. Read below about the background sound piece.

Many more visual results were obtained in the video recordings.  This material will be used with a myth-science sound piece to better portray the message and the background concept of this work.  Sonification of the microinteraction will also be an integration to this project to create dynamic interactive psychoacoustic soundscapes.  The myth-science sound piece project can be viewed in the following link:

ODE to Länadk. A Myth-Science Sound Piece.

(1) Contents of probiotic:

Bifidobacterium lactis, inulin, Lactococcus lactis, Lactobacillus plantarum, Lactobacillus acidophilus, Streptococcus thermophilus, Bifidobacterium longum, Lactobacillus rhamnosus, Lactobacillus bulgaricus, Bifidobacterium bifidum, Lactobacillus salivarius, Lactobacillus casei. Filler / Bulking agent: corn starch, modified starch / corn starch pregelatinized. Capsule Shell / Capsule shell: Hydroxypropylmethylcellulose, gellan. Release Agent / Anticaking agent: Magnesium stearate.

(2) Synbiotic:

1 Capsule of probiotic

10ml tap water

1ml salt

1ml yogurt