Optical device for parallel online measurement of dissolved oxygen and pH in shake flask cultures

We describe a new device with parallel optical measurement of dissolved oxygen (DO) and pH in up to nine shake flasks applicable in any conventional shaking incubator. Measurement ranges are 0-500% of air saturation for oxygen and 5.5-8.5 for pH. It was used to characterize growth profiles of different L-lysine producing strains of Corynebacterium glutamicum, of Saccharomyces cerevisiae and of Escherichia coli. Cultures in unbaffled flasks were highly reproducible. Oxygen limitation was indicated online which is particularly important when cultivating fast growing cells as E. coli. C. glutamicum strains showed distinct characteristic patterns of DO and pH indicating biological events. During the cultivation of S. cerevisiae on glucose, fructose and galactose, oxygen uptake rate was determined using the predetermined value of k(L)a. pH measurement was used to determine the minimum buffer requirement for a culture of C. glutamicum.