Online Monitoring of Cell Growth on PDMS-PDMS Reversible Microfluidic Bioreactor Integrated to Optical Fiber Sensor

A microfluidic bioreactor was fabricated by curing PDMS over 3D-printed molds, and it contains microchannels and perfusion chambers instrumented with optical fibers for the online analysis of the cellular growth. The channels were designed for allowing both the complete mixture of reagents and the possibility of generation of concentration gradients, and the perfusion chambers are isolated from them by polycarbonate membranes, providing a chemical environment with a constant concentration of nutrients for the cells. The optical fibers are laterally inserted in the chambers, and the monitoring of cells concentration is based on the quasi-elastic light scattering: as the total number of cells grows, there is an increase on the dispersion of the reflected intensity data, and the autocorrelation of the values allows the inference of the concentration. The sensor signals obtained during the fermentation of S. cerevisiae were equivalent to the cell counting on the Neubauer chamber using an optical microscope, leading to a value of the maximum specific growth rate pm of 0.50 h(-1). This optical monitoring system has proven to be easily manufacturable and capable of performing fast screening and online monitoring of the microbial kinetics.