Design and fabrication of a microbioreactor for yeast culturing

From the beginning of the 1980, a new platform called "microfluidics" has been appeared. Microfluidics generally means the miniaturization of devices and systems, and this field covers engineering, biochemistry and biotechnology with several applications. As an advantage of microfluidics, small reagent or sample volumes are employed through the systems, therefore excess consumption of materials can be prevented. Since microfluidic devices can handle many processes, they can decrease the dependency on conventional equipment, which are always expensive and time consuming. Therefore, biosystems engineering heads toward the microfluidic systems with yeast applications. Within the framework of this thesis, the design and fabrication of a microbioreactor for yeast culturing was performed. A design for yeast culturing was drawn via L-Edit layout program and a master was obtained. Microbioreactor was made of polymethyl methacrylate (PMMA) polymer, which is biocompatible material, and fabricated via hot embossing by employing the master and solvent-assisted bonding techniques. In order to optimize the parameters such as fluid flow, concentration distribution within the designed chip, COMSOL Multiphysics program was utilized. Before yeast experiment, polystyrene beads of 2 and 10μm diameter were tested through the fabricated chip to check its functionality for yeast culturing. The ultimate goal of this thesis was to get knowledge about the uncharacterized YOR060C protein in yeasts. Yeast preculture at optical density (OD) of 0.5 was fed through the microbioreactor and brightfield and fluorescence images of yeast cells within the chip were taken with CCD camera on the microscope. The experiment was lasted for approximately 28 hours and the images were processed via Fiji image processing package program. Cell count, cell area and cell perimeter were estimated from brightfield microscopy images and cell integrated density, the indicator of fluorescence luminescence, was obtained from fluorescence microscopy images. According to the obtained results, cell proliferation within the microbioreactor was successfully achieved, which approves the usage of the designed microbioreactor for further yeast culturing.