C. Helbig, T. Bchner, P. Gpel, M. Beuse
Introduction
Glucose is the most important nutrient source for Streptomyces spp.. The production of antibiotics after the exponential growth-phase in cultivations of Streptomyces spp. can be optimised by regulation of the glucose concentration in the media. Therefore comprehensive on-line monitoring of glucose is needed.
Methods
Streptomyces spp. cultivations with different feeds of glucose have been carried out in a 15 litres working volume bio-reactor (Biostat C, B. Braun Biotech Int.). Glucose concentrations in the complex media have been determined on-line with ProcessTRACE in combination with a dialysis probe (TRACE Analytics).
Fig. 1: Bioreactor connected to ProcessTRACE via dialysis probe.
The concentrations have been verified off-line by analysis with a hexokinase test-kit (Sigma Diagnostics). A schematic view on the experimental set-up is shown in figure 1.
Results
Figure 2 shows a comparison of the on-line and off-line data of the glucose concentrations along with the product concentration during one cycle of a repeated batch fermentation. The productivity is at its maximum. Figure 3 shows the same comparison in a batch fermentation over a period of 110 h.
Fig. 2: Glucose and product concentrations over a period of 100 h cultivation time of S. natalensis.
Discussion
Figure 2 and 3 show that the on-line monitoring with dialysis sampling method leads to data
Fig. 3: Concentrations of glucose analysed on- and off-line in a batch-fermentation of S. conglubatus.
for glucose concentrations, which correlate very well with the data from the off-line analysis. Over a period of more than 100 h no significant difference between on-line and off-line data is observed. Because of zero-volume sampling the probe is particularly suitable for small-scale fermenters in the field of research and process development. As it is possible to get data in very small intervals, a regulation of glucose concentrations in the cultivation vessel reacts very fast. With ProcessTRACE it is possible to detect glucose as well as lactate or methanol on-line in cultivations of other species.
Reference: Tollnick, C.; Beuse, M. (1999): Complete process monitoring; Chemical plants + processing, (4), 50-51.
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