Thermokinetic description of anaerobic growth of Halomonas halodenitrificans using a static microcalorimetric ampoule technique.

Efficiency and velocity of growth are key variables to consider when designing any microbial biotechnological process. Selection of the optimal strain and description of environmental effects on growth patterns require rapid information about relevant parameters. Calorimetry is particularly suitable for providing such data, provided it can simultaneously perform many measurements and the apparatus is as simple as possible. The simplest experimental set-up measures the heat flux of microorganisms growing in a static, sealed ampoule. But, how reliable and reproducible are the growth rates and growth yield coefficients obtained from such a system? To answer this question, the strain Halomonas halodenitrificans CCM 286(T) was grown on glycerol with nitrate as the terminal electron acceptor in a multi-channel isothermal heat conduction calorimeter in such a way that growth was predominantly influenced by availability of the oxidant. The time course of the heat fluxes up to the maximum attained was successfully modelled using integrated Monod kinetics. The reproducibility of the specific growth rate obtained was excellent (standard deviation less than 1% for a single measurement and less than 3% for a couple of measurements) and agreed well with figures reported in the literature. An Arrhenius-type model, consisting of one term for the activation and one for the inactivation of the microbial catalyst, was found to fit the whole specific growth rate versus temperature curve.