Introduction
The openPBR is a low-cost, easy to assemble and reliable option to cultivate phototrophic organisms. We have developed it as an open-source platform to operate as you need it. It comes in several setups, from nine cultivation vessels to three flat panels with a minimum width of 15 mm and up to a volume of 190 ml. It provides users with the ability to measure optical density at wavelengths from 400 nm to 800 nm, online and provides a .csv file output. All parts are openly available and even gas supply is exactly adjustable through a rotameter, depending on the needs of your organism and setup. We want to offer scientists a simple and versatile cultivation platform.
Sensors
Illumination
Gas mixing and pumps
Cultivation chamber
Casing
Overview of single components
Cultivation Chamber
The openPBR can be used with several different cultivation vessels. Originally designed to hold three 95 ml, fully autoclavable, flat panels, with interchangeable rings from 15 mm (95 ml) up to 30 mm width (190 ml). For growth-comparison studies, the openPBR can be set up with up to nine hybridization flasks with standard SCHOTT-45 cups. Even the use of cell-culture flasks is possible. For this use-case we 3D-printed autoclavable cups to connect them with hoses for classical cell-culture flasks.
Illumination
The LED panel of the openPBR is designed to give you full control of both color and intensity of the light source powered by 250 single RGB LEDs and 250 white LEDs with a total light intensity of up to 300 µE. Having a constant and reproducible light source in a photobioreactor setup is one of the most difficult tasks to achieve. To learn how to build and control your own please visit our step-by-step tutorial.
To get an impression of how to set up the relative voltage in the OBP-software to get the desired light intensity we developed a light intensity adjustment curve. We measured the light intensity at 24 different positions above the LED panel, each with the relative voltage set to 15, 140 and 225. Using these values we calculated a linear fit, which can be used to predict the light intensity at any given relative voltage.
Gas supply
Sensors
The sensory system of the openPBR consist of up to nine Opt 101 Monolithic linear voltage sensors and nine LEDs with the specific wavelength of 680 nm. It is possible to use any LED in the linear area of the sensor thus measurements from 400 nm to 800 nm are feasible.
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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Electronic
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.
Chemostat equation
Light Gradient
OD Measurement
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.
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!
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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