Evaluation of a portable Arduino-based mini spectrometer prototype for cells optical density measurement

Abstract

Cell optical density (OD) measurement is essential for tracking the progress of microbial fermentation processes. It is typically performed through a spectrophotometer at the wavelength of 600 nm. In this paper, a portable Arduino-based mini spectrometer prototype is presented. In the proposed prototype, a turbidity sensor was utilized to perform the optical density measurement of cells based on the Beer’s Lambert law. Differences on the light intensity from the excitation source and the collective point were correlated with the known cell concentration (using S. cerevisae yeast with concentration between 1 g/L and 5 g/L). The data attained was used as the standard curve and also to validate the functionality of the device. Fermentation experiments were carried out and the progress of the fermentation were measured using the proposed OD sensing prototype and compared to the standard bench top spectrometer. Both devices produced a calibration curve with R-squared value greater than 0.95 (0.95 for bench spectrometer and 0.97 for the Arduino device) and a comparable fermentation curve attained from both devices highlighted the workability of the proposed prototype. In addition, the device has a small footprint, portable and affordable.