Advances in Applied Probability

Stochastic models for a chemostat and long-time behavior

Pierre Collet, Servet Martínez, Sylvie Méléard, and Jaime San Martín

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We introduce two stochastic chemostat models consisting of a coupled population-nutrient process reflecting the interaction between the nutrient and the bacteria in the chemostat with finite volume. The nutrient concentration evolves continuously but depends on the population size, while the population size is a birth-and-death process with coefficients depending on time through the nutrient concentration. The nutrient is shared by the bacteria and creates a regulation of the bacterial population size. The latter and the fluctuations due to the random births and deaths of individuals make the population go almost surely to extinction. Therefore, we are interested in the long-time behavior of the bacterial population conditioned to non-extinction. We prove the global existence of the process and its almost-sure extinction. The existence of quasi-stationary distributions is obtained based on a general fixed-point argument. Moreover, we prove the absolute continuity of the nutrient distribution when conditioned to a fixed number of individuals and the smoothness of the corresponding densities.

Article information

Adv. in Appl. Probab., Volume 45, Number 3 (2013), 822-837.

First available in Project Euclid: 30 August 2013

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Mathematical Reviews number (MathSciNet)

Zentralblatt MATH identifier

Primary: 60J25: Continuous-time Markov processes on general state spaces 60J27: Continuous-time Markov processes on discrete state spaces 92D25: Population dynamics (general)

Population process chemostat extinction quasi-stationary distribution


Collet, Pierre; Martínez, Servet; Méléard, Sylvie; San Martín, Jaime. Stochastic models for a chemostat and long-time behavior. Adv. in Appl. Probab. 45 (2013), no. 3, 822--837. doi:10.1239/aap/1377868540.

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