Illuminated Orbital Shaker for Microalgae Culture v1
Authors: Nedbal Jakub 
Published: March 2020

Microalgae are grown for the research on photosynthesis, biotechnology, and water-environment ecology. Specialized laboratories typically use calibrated commercial equipment, which agitates the microalgae culture by shaking or bubbling, controls the irradiance, temperature, and CO2 content. Such commercial incubators may be out of reach for some laboratories, like those not specializing in microalgae research, teaching laboratories, or laboratories in low resource settings. Our research uses microalgae cultures during the development and validation of advanced microscopy techniques. We lacked access to and the budget for a commercial incubator. We solved the problem by building a stand-alone orbital shaking incubator with an in-built variable light source and a 24-hour timer. The shaker features a homogeneously illuminated growth area of 20 cm × 15 cm, which is suitable for three T75 tissue culture flasks or four 100 ml Erlenmeyer flasks. The overall material cost was around £300 and assembly time of about two days. We tested the shaker with fresh-water microalgae Desmodesmus quadricauda and Chlorella vulgaris. Both microalgae cultures have been grown continuously for seven months in the incubator. We studied their growth under different light conditions to validate the function of the shaker. The protocol outlines the step-by-step process to the building of this microalgae shaker. Here, we describe an illuminated orbital shaker designed for culture of microalgae suspensions. It was optimized for production cost, simplicity, low power consumption, design flexibility, and consistent and controllable growth light intensity. The instrument agitates and illuminates microalgae suspensions grown inside flasks. The agitation speed is variable while the light intensity is both variable and programmable (24-hour light/dark diurnal cycle). The instrument offers a vastly cheaper alternative to commercial instruments for many laboratory applications, making it especially well suited for teaching and poorly-resourced research laboratories. It improves on home-built microalgae growth systems by offering consistent and well characterized illumination light intensity, low power consumption and heat dissipation. The illuminated growth area is 20 cm × 15 cm, which is suitable for three T75 tissue culture flasks or six 100 ml Erlenmeyer flasks. The photosynthetic photon flux density, measured inside an Erlenmeyer flask, is variable in eight steps (26−800 μmol·m−2·s−1). The overall material cost is around £300 (including an entry-level orbital shaker). The build takes about two days, requiring electronics assembly and machine workshop skills. The instrument build is documented in a set of protocols, design files, and source code. Its design can be readily modified, scaled, and adapted for other orbital shakers and specific experimental requirements. The illuminated orbital shaker is ideal for growing small volumes of microalgae for research and teaching. It can readily replace commercial systems in many common microalgae culture application for a fraction of their cost. It outperforms typical home-made systems by offering consistent and predictable illumination light intensity and low power consumption.