A new balance equation of reducing equivalents for data consistency check and bioprocess calculation.

The reducing equivalent (RE) balance is a basic equation for data consistency check and calculations of bioprocesses. The macroscopic approach is often used because it does not require detailed knowledge of metabolic pathways. In this work, the conventional Minkevich-Eroshin balance equation is examined with data of anaerobic glycerol conversion by Klebsiella pneumoniae and Clostridium butyricum as examples. It is shown that the Minkevich-Eroshin equation is very insensitive to measurement errors in products of less dominance and/or with relatively low reductance degree. Relatively large deviations from experimental values are encountered when the Minkevich-Eroshin equation is used for the calculations of these products. To overcome some of these shortcomings an improved RE balance equation is proposed that is based on 'reductance equations' of substrate conversion into the individual carbon containing products (including biomass). The proposed new equation significantly improves the performance of the RE balance equation for data consistency check and for the calculations of unknown variables with relatively low reductance degree. The rationale for this is that it considers merely the REs that really participate in the bioreactions. The use of the proposed method requires no detailed knowledge of metabolic pathways and is therefore of macroscopic nature. It can be reduced to the pathway balance equation if the pathways are known.