Analysis of noise and bias in fermentation oxygen uptake rate data

The calculation of many derived fermentation variables such as the respiratory quotient (RQ) and mass transfer coefficient ( K L a ) requires the differences between the molar percentages of oxygen and carbon dioxide in the fermentor inlet and exit gas, called the %OUR and %CER. Noise and bias in %CER data is of order that in the exit gas carbon dioxide analysis. However, the relative amount of noise in the %OUR is one to two orders of magnitude greater than the noise in the raw oxygen analyses because the %OUR is calculated as a small difference between two large quantities. The noise in the %OUR is white with a Gaussian amplitude probability distribution of absolute standard deviation 0.0145. A chi‐square filter of the %OUR data is shown to considerably improve the quality of the calculated RQ and K L a for a fermentation of Streptomyces clavuligerus . © 1992 John Wiley & Sons, Inc.