Initial conditions-dependent growth kinetics in microbial batch culture

The ratio of initial substrate concentration (S0) to initial biomass concentration (X0) represents the availability of carbon and energy source for microbial growth in a batch culture. Based on the concept of consecutive catabolism and anabolism, a thermodynamic approach was used to derive the expression of the specific growth rate to S0/X0, which shows that microbial growth kinetics are determined by the S0/X0 ratio in batch culture, while the constants involved in the proposed model have clearly defined physical meanings. The proposed model was verified by the experimental data obtained at different S0/X0 ratios, while literature data also supported the model derived. This study provides theoretical evidence that the S0/X0 ratio is the most important determinant of kinetic ability of microorganisms in a batch culture. When batch culture is chosen to evaluate the kinetic parameters for process design and ready biodegradability of substances, care is required in designing initial conditions of batch culture since microbial growth kinetics is highly influenced by the S0/X0 ratio.