Parameter identification of thermophilic anaerobic degradation of valerate

Mathematical model of the decomposition of valerate presents 3 unknown kinetic parameters, 2 unknown stoichiometric coefficients and 3 unknown initial concentrations for biomass. Applying a structural identifiability study, it is concluded that it is necessary to perform simultaneous batch experiments have been done at 55 degree C, charcterised by four different initial acetate concentrations. Product inhibition of valerate degradation by acetate is considered. Practical identification has been done optimising the sum of the multiple determination coefficients for all measured state variables and for all experiments simultaneously. The estimated values of kinetic parameters have been 0.676 d^-1 for the maximum growth rate (um), 0.176 g Val/L for the saturation constant (Ks) and 0.405 g Ac/L for the constant of acetate inhibition (Kin), considering Monod kinetics and a non-competitive inhibition form. Stoichiometry of valerate anaerobic decomposition has also been established, with the following yeild coefficients: 0.072 g biomass/g Val, 0.52 g Ac/g Val and 0.73 g Pr/g Val. Kinetic parameter values are not significantly different from kinetic values for butyrate anaerobic degradation found in the literature. Results have bann characterised by the parameter correlation matrix and applying the t-Student test at 5% significance level with positive results except for Ks parameter, for which more experiments for improving its identifiability should be done.