On-line stoichiometry and identification of metabolic state under dynamic process conditions

A method for the online calcn. of conversion rates and yield coeffs. under dynamic process conditions was developed. The method is based on cumulated mass balances using a moving av. method. Elemental balances were used to test the measured cumulated quantities for gross errors and inappropriate stoichiometry definition followed by data reconciliation and estn. of non-measured conversion rates, using a bioprocess set-up including multiple online anal. techniques. The quant. potential of the proposed method is demonstrated by executing transient expts. in aerobic cultures of Saccharomyces cerevisiae on glucose. Rates and yield coeffs. could be consistently quantified in shift-up, shift-down, and accelerostat expts. The method shows the capability to describe quant. transient changes in metab. including uncoupling of catabolism and anabolism, also for the case when multiple components of metab. are not measured. The validity of the expt. can be evaluated online. Addnl., the method detects with high sensitivity inappropriate stoichiometry definition, such as a change in state of metab. It was shown that concn. values can be misleading for the identification of the metabolic state. In contrast, the proposed method provides a clear picture of the metabolic state and new physiol. regulations could be revealed. Hence, the novelty of the proposed method is the online availability of consistent stoichiometric coeffs. allowing a significant speed up in strain characterization and bioprocess development using minimal knowledge of the metab. Addnl., it opens up the use of transient expts. for physiol. studies. [on SciFinder (R)]