Feed rate noise modulates autocatalysis and shapes the oscillations of the Belousov–Zhabotinsky reaction in a continuous stirred tank reactor

Abstract

Metabolism, just like other functions in living systems, involves chemical oscillators, and the detailed metabolic oscillation profiles reflect the preferential pathways in the complex metabolism reaction network, as well as the thermodynamics of metabolism. Living systems are open and subject to a noisy environment; hence it is natural to question how noisy reactant intake affects the chemical response, i.e. the detailed resulting oscillations, of an open complex chemical oscillatory system. In this paper, we use a chemical analogue of noisy “metabolism”, by applying white Gaussian noise on the feed rates of the [Ru(bpy)₂]³⁺ catalyzed Belousov–Zhabotinsky (B–Z) reaction running in a continuous stirred tank reactor (CSTR). The noise was applied to the flow rate of a reactant one at a time, in the excitability region (near the Hopf bifurcation), and we observed its effect on the dynamical response, e.g. the features of the noise-induced oscillatory profiles. We show experimentally that noise on a specific reactant tunes the shape of the relaxation oscillations, and we link the observed effects to the most affected subnetworks in the Field–Körös–Noyes (FKN) mechanism. Hence, the autocatalytic loop is most affected by the noise on the acid feed rate and on the bromate feed rate pumping systems. This tuning of the oscillation shape together with the more studied ability to tune the amplitude and period of the noise oscillations by the noise parameters allows achieving distinct oscillations (shape + period + amplitude) not attainable in deterministic operation. Furthermore, noise on a specific reactant feed can thus be used to direct the reaction to a given pathway. Our results can be used to develop methods to force chemical and/or biological systems into desired dynamical regimes not otherwise easily attainable.