On the use of the pH control reagent addition rate for fermentation monitoring

Abstract

The linear relation between the pH control reagent addition rate, the net conversion rates of metabolites, the carbon dioxide mass transfer rate and the feed rates is developed and shown to have the same form for batch, fed-batch, and continuous reactors, regardless of the number of feeds. The magnitudes of various biological and solution chemistry effects on the pH control reagent addition rate are estimated to be negligible, facilitating the use of the pH control reagent addition rate as a straightforward indicator of primary metabolism. Finally, application of the linear relation, termed the abiotic proton balance, is discussed for a number of fermentation processes. (c) 1995 John Wiley & Sons, Inc.

Use of the abiotic proton balance for determining linear relations among net conversion rates of primary metabolites in fermentation processes

“…(6) is missing in eq. (54) of the original article (Siano, 1995).] The rre, is the pH control reagent addition rate (mol reagL-h), f,, is the proportionality constant for proton formation for the metabolite (mol H+/mol met), greag is the proportionality constant for proton neutralization for the reagent (mol reag/mol H+), ZrH,in is the proton formation rate due to the sum of the feeds (mol H+/L-h), rc0, is equivalent to CEWV,, CER is the CO, evo- lution rate (mol C02/h), V, is the volume of the liquid (L), and CTR is the CO, transfer rate (mol CO,/h).…”

“…(20) of Siano 1995 [but must often be determined experimentally (Siano, 1995)] and [The negative sign in Eq. (6) is missing in eq.…”

“…[The CrH,in will be zero when feeds are not used or when the feeds and fermentor are at the same pH and similar ionic strengths (Siano, 1995).] The APB is applicable for batch, fed-batch, and continuous reactors (Siano, 1995). Equation (20 represents a fifth independent balance, derived from Eq.…”

“…The rre, is the pH control reagent addition rate (mol reagL-h), f,, is the proportionality constant for proton formation for the metabolite (mol H+/mol met), greag is the proportionality constant for proton neutralization for the reagent (mol reag/mol H+), ZrH,in is the proton formation rate due to the sum of the feeds (mol H+/L-h), rc0, is equivalent to CEWV,, CER is the CO, evo- lution rate (mol C02/h), V, is the volume of the liquid (L), and CTR is the CO, transfer rate (mol CO,/h). [The CrH,in will be zero when feeds are not used or when the feeds and fermentor are at the same pH and similar ionic strengths (Siano, 1995).] The APB is applicable for batch, fed-batch, and continuous reactors (Siano, 1995).…”

“…The abiotic proton balance (APB) is an available linear relation between the pH control reagent addition rate and the net conversion rates of the pH-affecting primary metabolites for fermentations at constant pH (Siano, 1995). Incorporation of the APB into the balancing matrices introduces an additional independent equation and an additional rate (r,,,, based on the pH control reagent addition rate), and therefore does not decrease the number of degrees of freedom, i.e., the number of rate measurements that must be taken to determine the entire set of net conversion rates.…”