Kinetics of Vinyl Acetate Biodegradation by Pseudomonas fluorescens PCM 2123

Abstract

The microbial degradation of vinyl acetate (VA) by Pseudomonas fluorescens PCM 2123 strain was studied in both batch and continuous modes. The purpose of the experiments was to determine the kinetic model of the cell growth and biodegradation rate of vinyl acetate (VA), which was the sole carbon and energy source for tested microorganisms. The experiments, carried out in a batch reactor for several initial concentrations of growth substrate in the liquid phase ranging from 18.6 to 373 g_substrate·m⁻³ (g_s·m⁻³) made it possible to choose the kinetic model and to estimate its constants. The Haldane inhibitory model with the values of constants: μ_m = 0.1202 h⁻¹, K_S = 17.195 g_s·m⁻³, K_i = 166.88 g_s·m⁻³ predicted the experimental data with the best accuracy. To set the parameters of maintenance metabolism it was necessary to carry out a series of continuous cultures at different dilution rates (0.05 to 0.072 h⁻¹) and concentrations of VA in the liquid supplied to the chemostat ranging from 30.9 to 123.6 g_s·m⁻³. The obtained data-base enabled to determine the coefficient for maintenance metabolism (m_e = 0.0251 g_substrate g_{cell dry weight}⁻¹·h⁻¹ (g_s·g_cdw⁻¹·h⁻¹)) as well as the maximal and observed values of yield coefficients, Y_{xs M} = 0.463 g_cdw·g_s⁻¹ and (Y_xs)_obs = 0.411 g_cdw·g_s⁻¹, respectively. The developed kinetics was verified by comparison of the computed and obtained in batch experiments profiles of changes in biomass and growth substrate concentrations.