Introduction
Producing reliable cultivation data can be fairly difficult, time consuming and pricey.
We decided to adress this problem by creating OPEN PBR, a modular cultivation setup for photosynthetic organisms with up to 9 separate cultivation vessels.
While gathering knowledge with our efforts in Human Practices, we quickly recognized the need for a platform that enables the user to vary many parameters during cultivation of microalgae while still being affordable and capable of generating reproducible data.
The OPEN PBR fulfills these demands by providing a modular setup for cultivation of algae in turbido- or chemostat mode. With all components defined an openly available, it remains highly modular while using standardized vessels to provide reproducibility.
By using an existing model of general equations describing a chemostat with light as limiting substrate, we were able to pin down necessary functions and devices for performing them. For easy assembly of the device, files for lasercutting, a list of components and where to order them and an assembly guideline are provided below.
Chemostat equation
Light Gradient
OD Measurement
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Designing the bioreactor
Chemostat Equation
This chapter gives an overview over important parameters for cultivation resulting from the general chemostat equation.
The chemostat equation which we treated as a part of modeling provides us with an overview of general parameters important to a microbial culture. If we want to cultivate in turbidostat-mode, we need to remove liquid from the culture continuously. This removing is quantified through dilution rate \( D \): \begin{equation} D = \frac{1}{V_{c} \cdot \frac{\mathrm{d}}{\mathrm{d}t} V_{in} } \end{equation} \begin{array}{r l} V_c:& \text{Volume of culture in} mL \\ V_{in}: & \text{Volume of added medium in} mL \end{array} This equation shows us how
Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
Light Gradient
An important aspect of photosynthetic growth is illumination. Read about the light environment in a cultivation vessel here.
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Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
OD Measurement
With the same equation describing the light gradient inside the culture, we can define a relationship to measure cell density and other parameters.
Measurement of \(OD\) is based on the Beer-Lambert law (see our model for further information). From this law, \(OD\) is defined as:
\begin{equation} OD = - log(\frac{I(\lambda)}{I_0(\lambda)}) = \epsilon_X \cdot c_X \cdot d \end{equation}
\newcommand\T{\Rule{0pt}{1em}{.3em}}
\begin{array}{r l}
I_0(\lambda, t): & \text{light intensity upon entrance into vessel in} \: \frac{\mu mol}{m^2 \cdot s} \\
\epsilon_X: & \text{light attenuation coefficent for algae in} \: \frac{L}{mol \cdot cm} \\
bg: & \text{background turbidity} \: \frac{1}{cm} \\
d: & \text{light path in} cm
\end{array}
Generally speaking, realization of the setup should make the variables in the equation as indifferent to parameters that have an impact on measurement as possible.
Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
Sensors
Illumination
Gas mixing and pumps
Cultivation vessel
Casing
Overview of single components
In this chapter, we give an overview for all functions and components of the system. The aim is to serve as an introduction for assembling the system with the instructions provided in the last chapter.
Sensors
In this chapter, we will show you the sensors we are implementing in our setup. We build our own photometer and are using a prebuilt thermometer for temperature monitoring.
This already defines the components we need for measuring amount of algae cells, an LED that emits light ( \(I_0)\) ), a sensor that detects light after passage through the vessel and the vessel itself. It is important to measure under the same conditions every time, because otherwise \( I_0 \) can vary due to scattering of light at the vessel.
Linearer Opt 101 in wichtigem Bereich (PAR)
Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
Illumination
Here we want to explain our thoughts for illumination of the culture. An important aspect of illumination of photosynthetic cultures is intensity and wavelength distribution of light, which are explained here.
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Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
Gas mixing and pumps
For operating our culture in chemostat mode, we need pumps for transportation of medium in and out of our culture vessel as well as for mixing of gas into the culture for growth. This chapter aims to explain important parameters while choosing a pump for the setup.
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Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
Cultivation vessel
Because of Human Practices and Modeling, we decided to build a flat-panel cultivation vessel for our culture. Here we briefly explain our thoughts while building our own vessel and choosing vessels that fit our cultivation setup.
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Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
Casing
We shortly explain necessary properties of the case that holds our cultivation setup.
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Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
Github Project
Tools
PDF Instructions
Assembly Instructions
This chapter provides you with everything you need to rebuild our setup on your own - including software, a list of used parts and assembly instructions.
Github Project
Visit our Github page, where assembly instructions, list of parts and software are provided together and are kept up to date!
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Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
Tools
Container preview
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Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
PDF Instructions
Look at our PDF instructions where we provide you with a detailed step-by-step tutorial to build your own OPEN PBR!
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Fig. 1. Universal MoClo fusion sites.
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Fig. 2. Blablabla.
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