Substrate gradient formation in the large-scale bioreactor lowers cell yield and increases by-product formation

Abstract

A heterogeneous micro-environment was identi®ed in a 12 m 3 bioreactor with a height-to-diameter ratio of 2.5. The reactor was aerated by a ring sparger and stirred by three Rushton turbines. E. coli cells were cultivated in minimal medium to a cell density in the order of 30 g/l. Samples of glucose, the growth limiting component fed to the process, were taken at three levels in the bioreactor (top/middle/bottom). These showed that glucose concentration declined away from the feedpoint. The gradients depended on the mixing characteristics of the feedpoint, and concentrations of up to 400 times the mean value were found when feed was added to a relatively stagnant mixing zone. This resulted in up to 20% lower biomass yield compared to the bench scale. Gradients also affected the by-product formation, resulting in acetate formation in the large-scale bioreactor.

The Scale‐Up of Microbial Batch and Fed‐Batch Fermentation Processes

“…The use of LES also shows the temporal as well as the spatial concentration fluctuations of the glucose concentration in the vicinity of the feed point. Indeed, this was confirmed experimentally showing that cells were frequently exposed to peak glucose concentrations several times higher than the mean in the addition zone and that spatially dependent concentration gradients exist in large-scale fedbatch fermentation processes with a declining glucose concentration found with increasing distance from the feed point (Bylund et al, 1998). In laboratory scale bioreactors on the other hand, where much development work is done, mixing times are low (<~5s) and essentially significant temporal or spatial variations in concentration do not exist (Nienow, 1998).…”

“…In an E. coli fed-batch recombinant protein process, the maximum cell density reached was found to be 20% lower when scaling-up from 3l to 9 m 3 and the pattern of acetic acid formation had changed. (Bylund et al, 1998). During another study (Enfors et al, 2001), the performance of a recombinant strain of E. coli during fed-batch culture was found to vary on scale-up from the lab-scale to 10-30 m 3 industrial bioreactors.…”

Bench-scale Overproduction and Purification of recombinant GCSF in Escherichia coli fed-batch process

“…Type of E. coli strain influences on acetate production in aerobic fermentation processes (Phue and Shiloach, 2005;Rao et al, 2008) and take places when growth rate on glucose is high, (Phue and Shiloach, 2005;Shiloach and Fass, 2005) oxygen concentration is low (Phue and Shiloach, 2005;Bylund et al, 1998) and glucose concentration is excess (Phue and Shiloach, 2005;Bylund et al, 1998;Thiry and Cingolani, 2002). Then heterogeneous condition due to scale up makes points with excess glucose and low oxygen concentration (Bylund et al, 1998), thereby acetate production is increased in larger bioreactor.…”

Complete reuse of raw fishmeal wastewater: Evidence from a field cultivation study and economic analysis

“…It has been known that the biological properties such as metabolic reactions of microorganisms are dependent upon scale-up [25]. In comparison to the lab-scale, the typical differences in large-scale are reduced biomass yield, increased by-products production and the presence of limiting substrate gradient as measured at different heights in the bioreactor [36,37]. Therefore, such quality of liquid fertilizer produced in large-scale was necessary to compare with those that were produced under different culture conditions.…”