Images acquisition of multiphase dispersions in fermentation processes

Abstract

Multiphase mixing is a common operation in fermentation process. However, one of the main problems for online automatic monitoring of dispersions occurring in microbial cultures in a mechanically stirred bioreactor, is the difficulty in acquiring images (in motion) clear enough to characterize its elements (mainly air, water, oil and biomass) and their interactions during cultivation. Once the images to be analyzed have been acquired, other problems arise related to the complexity and diversity of objects/artifacts captured in the visual field. The heterogeneous transparency of some objects, low contrast and similarity between different classes of objects are, among others, major problems for the automation of image analysis procedures. The purpose of this work is to present a system that allows the on-line acquisition of images inside a mechanically stirred tank.The images are digitally obtained by connecting a TV camera to a stereomicroscope. The scanning of the camera is synchronized to the flashing of a stroboscope, which acts as the light source and is equipped with a submergible probe. These illumination conditions allow obtaining high quality images that can be further analyzed to quantify size distributions of air bubbles and oil drops in multiphase dispersion, and to observe the dynamics of phase interactions (solid, liquid and gaseous) in a model culture.