  Self-cycling fermentation is an automated process used for culturing
microorganisms. We consider a model of $n$ distinct species competing for a
single non-reproducing nutrient in a self-cycling fermentor in which the
nutrient level is used as the decanting condition. The model is formulated in
terms of impulsive ordinary differential equations. We prove that two species
are able to coexist in the fermentor under certain conditions. We also provide
numerical simulations that suggest coexistence of three species is possible and
that competitor-mediated coexistence can occur in this case. These results are
in contrast to the chemostat, the continuous analogue, where multiple species
cannot coexist on a single nonreproducing nutrient.
