Microbial competition: Study of global branching phenomena

The stability characteristics of a bioreactor with cell recycle involving t he competition between microbial cultures are investigated. The unstructure d model, based on Andrew's inhibitory kinetics, involves the pure and simpl e competition between two microorganism for a single pollutant. The singula rity theory used for this study allows an in-depth analysis of both the sta tic and dynamic bifurcation mechanisms occurring in the system. The hystere sis with five solutions is the highest singularity the system can exhibit. With inhibitory kinetic expressions, the model can also predict self-sustai ned oscillations for a wide range of parameters. The analysis of clean feed conditions shows that the model cannot exhibit periodic behavior regardles s of the growth kinetics model. Analytical criteria are also derived for th e coexistence of the competing cultures and for the prevention of wash-out conditions. The stability characteristics for Monod kinetics, derived as a limiting case of the inhibitory kinetic expressions, are incorporated in th e general framework offered by the singularity theory.