Scale‐down studies for the scale‐up of a recombinant Corynebacterium glutamicum fed‐batch fermentation; loss of homogeneity leads to lower levels of cadaverine production

BACKGROUNDThe loss of efficiency and performance of bioprocesses on scale‐up is well known, but not fully understood. This work addresses this problem, by studying the effect of some fermentation gradients (pH, glucose and oxygen) that occur at the larger scale in a bench‐scale two‐compartment reactor (Plug flow reactor (PFR) + Stirred tank reactor (STR)) using the cadaverine‐producing recombinant Corynebacterium glutamicum DM1945 Δact3 Ptuf‐ldcC_OPT. The new scale‐down strategy developed here studied the effect of increasing the magnitude of fermentation gradients by considering not only the average cell residence time in the PFR (τPFR), but also the mean frequency at which the bacterial cells entered the PFR (fm) section of the two‐compartment reactor.RESULTSOn implementing this strategy the cadaverine production decreased on average by 26 %, 49 % and 59 % when the τPFR was increased from 1 min to 2 min and then 5 min respectively compared to the control fermentation. The CO2 productivity was highest (3.1‐fold that of the control) at a τPFR of 5 min, but no losses were observed in biomass production. However, the population of viable but non‐culturable cells increased as the magnitude of fermentation gradients was increased.CONCLUSIONThis study demonstrated that C. glutamicum DM1945 Δact3 Ptuf‐ldcC_OPT physiological response was a function of the magnitude of fermentation gradients simulated. The adaptations of a bacterial cell within a heterogeneous environment ultimately result in losses in fermentation productivity as observed here.</div

Supplementary information files for 'Scale‐down studies for the scale‐up of a recombinant Corynebacterium glutamicum fed‐batch fermentation: loss of homogeneity leads to lower levels of cadaverine production'

Supplementary information files for 'Scale‐down studies for the scale‐up of a recombinant Corynebacterium glutamicum fed‐batch fermentation: loss of homogeneity leads to lower levels of cadaverine production'Abstract:BACKGROUNDThe loss of efficiency and performance of bioprocesses on scale‐up is well known, but not fully understood. This work addresses this problem, by studying the effect of some fermentation gradients (pH, glucose and oxygen) that occur at the larger scale in a bench‐scale two‐compartment reactor (Plug flow reactor (PFR) + Stirred tank reactor (STR)) using the cadaverine‐producing recombinant Corynebacterium glutamicum DM1945 Δact3 Ptuf‐ldcC_OPT. The new scale‐down strategy developed here studied the effect of increasing the magnitude of fermentation gradients by considering not only the average cell residence time in the PFR (τPFR), but also the mean frequency at which the bacterial cells entered the PFR (fm) section of the two‐compartment reactor.RESULTSOn implementing this strategy the cadaverine production decreased on average by 26 %, 49 % and 59 % when the τPFR was increased from 1 min to 2 min and then 5 min respectively compared to the control fermentation. The CO2 productivity was highest (3.1‐fold that of the control) at a τPFR of 5 min, but no losses were observed in biomass production. However, the population of viable but non‐culturable cells increased as the magnitude of fermentation gradients was increased.CONCLUSIONThis study demonstrated that C. glutamicum DM1945 Δact3 Ptuf‐ldcC_OPT physiological response was a function of the magnitude of fermentation gradients simulated. The adaptations of a bacterial cell within a heterogeneous environment ultimately result in losses in fermentation productivity as observed here.</div

Expansion of human mesenchymal stem/stromal cells on temporary liquid microcarriers

Background: Traditional large scale culture systems for human mesenchymal stem/stromal cells (hMSCs) use solid microcarriers as attachment substrates. While the use of such substrates is advantageous due to the high surface-to-volume ratio, cell harvest from the same substrates is a challenge as it requires enzymatic treatment, often combined with agitation. Here, we investigated a two-phase system for expansion and non-enzymatic recovery of hMSCs. Perfluorocarbon droplets were dispersed in a protein-rich growth medium and were used as temporary liquid microcarriers for hMSC culture. Results: hMSCs successfully attached to these liquid microcarriers exhibiting similar morphologies to those cultured on solid ones. Fold increases of 3.03±0.98 (hMSC1) and 3.81±0.29 (hMSC2) were achieved at day 9. However, the maximum expansion folds were recorded at day 4 (4.79±0.47 (hMSC1) and 4.856±0.7 (hMSC2)). This decrease was caused by cell aggregation upon reaching confluency due to the contraction of the interface between the two phases. Cell quality as assessed by differentiation, cell surface marker expression and clonogenic ability was retained post-expansion on the liquid microcarriers. Cell harvesting was achieved non-enzymatically in two steps, by firstly inducing droplet coalescence, then aspirating the interface. hMSCs’ quality characteristics continued to be retained even after inducing droplet coalescence.Conclusion: The prospect of a temporary microcarrier that can be used to expand cells and then ‘disappear’ for cell release without using proteolytic enzymes is a very exciting one. Here, we’ve demonstrated that hMSCs can attach and proliferate on these perfluorocarbon liquid microcarriers, while very importantly retaining their quality.</div

Supplementary figures for "Process development of human multipotent stromal cell microcarrier culture using an automated high-throughput microbioreactor"

Supplementary information files for "Process development of human multipotent stromal cell microcarrier culture using an automated high-throughput microbioreactor"<div><br></div><div><p><b>Figure S1</b>. Growth kinetics of hMSCs donor 2 cells using serum-free (SFM) and fetal bovine serum (FBS)-based media in both the ambr15 and spinner flasks with data showing the viable cell density.</p><p><br></p><p><b>Figure S2</b>. Nutrient and metabolite flux for hMSC donor 1 cells expanded on microcarriers in the serum-based and serum-free cultures in both the ambr and spinner flasks.</p><p><br></p><p><b>Figure S3</b>. Functional characterisation of hMSCs from donor 1 harvested from the serum-free ambr15 bioprocess.</p><p><br></p><h2>ABSTRACT</h2><p>Microbioreactors play a critical role in process development as they reduce reagent requirements and can facilitate high-throughput screening of process parameters and culture conditions. Here, we have demonstrated and explained in detail, for the first time, the amenability of the automated ambr15 cell culture microbioreactor system for the development of scalable adherent human mesenchymal multipotent stromal/stem cell (hMSC) microcarrier culture processes. This was achieved by first improving suspension and mixing of the microcarriers and then improving cell attachment thereby reducing the initial growth lag phase. The latter was achieved by using only 50% of the final working volume of medium for the first 24 h and using an intermittent agitation strategy. These changes resulted in >150% increase in viable cell density after 24 h compared to the original process (no agitation for 24 h and 100% working volume). Using the same methodology as in the ambr15, similar improvements were obtained with larger scale spinner flask studies. Finally, this improved bioprocess methodology based on a serum-based medium was applied to a serum-free process in the ambr15, resulting in >250% increase in yield compared to the serum-based process. At both scales, the agitation used during culture was the minimum required for microcarrier suspension, N_JS. The use of the ambr15, with its improved control compared to the spinner flask, reduced the coefficient of variation on viable cell density in the serum containing medium from 7.65% to 4.08%, and the switch to serum free further reduced these to 1.06–0.54%, respectively. The combination of both serum-free and automated processing improved the reproducibility more than 10-fold compared to the serum-based, manual spinner flask process. The findings of this study demonstrate that the ambr15 microbioreactor is an effective tool for bioprocess development of hMSC microcarrier cultures and that a combination of serum-free medium, control, and automation improves both process yield and consistency.</p></div