The effect of non-biological particulates on microbial cell disruption in a slurry bioreactor

Bibliography: leaves [177]-191.Cell damage from hydrodynamic stress is an important consideration in biological systems since it can result in the growth and function of the cell becoming impaired (Toma et al. 1991, Lilly et al. 1992). In the extreme case of cell damage, cell disruption occurs. This dissertation presents the results of an investigation into the disruption of stationary-phase microbial cells in a stirred tank reactor when agitated in the presence of biologically inert solid particles in the absence of aeration. Applications of biological processes, where cells and solid particles are used, include bead mills, minerals bioprocessing, soil bioremediation and immobilised biocatalysts. An understanding of the rate, extent and mechanisms of cell disruption in these systems will facilitate the design of bioreactors to minimise or maximise microbial cell disruption, depending on the application. The primary objectives were to quantify and model the effect of incompletely and completely suspended solids on the kinetics of cell disruption, as a function of the solids concentration, agitation intensity and impeller flow pattern. Saccharomyces cerevisiae was used as model micro-organism and silica as the solid particles. Modelling the cell disruption enabled its prediction as a function of the operating parameters and further allowed the cell disruption mechanisms to be elucidated. A final objective was to quantify the solids suspension as a function of the operating parameters