Does single-use make sense for fermentation?
Single-use bioprocessing technology offers increased speed, efficiency, and economy compared with stainless steel equipment when used in animal cell culture processes. But can it do the same if used in microbial fermentation, which has its own specific requirements and challenges? We wanted to find out, so we set up a comparison between fermentation in single-use versus stainless steel equipment. In this article, we take a look at the key results and takeaways.
We have tested four hypothetical situations to investigate
Stainless steel and glass equipment have historically been used in microbial fermentations, which require sufficient mass transfer of oxygen and the removal of excess metabolic heat. The deployment of single-use equipment is less common. We set out to understand the economic implications of using a disposable strategy and to identify scenarios where single-use technology might be more favourable than traditional stainless steel equipment. To do so, we created a model of an E.coli dAb process.
We focused on the upstream fermentation process and the dAb production phase, looking at process economy in four hypothetical scenarios:
- Single-product facilty with stainless steel equipment
- Single-product facility with single-use equipment
- Multi-product facility with stainless steel equipment
- Multi-product facility with single-use euqipment
The single-use fermentor was the Xcellerex XDR-50 MO system, while the stainless steel Biostat™ D-DCU 50 L fermentor (Sartorius Stedim Biotech) was used as a reference.
Single-use boosts production and increases agility
The results show that single-use technology can increase annual production capacity up to 100%, thanks to faster batch changeover. Although we found that production cost per batch can be higher with single-use, the increased batch throughput means greater profit opportunties. Plus, single-use represents reduced financial risk, giving businesses increased agility.
Let’s look more closely at how we arrived at these results.
Faster fermentation, more batches
The model we created worked on the assumption that 300 days are available for fermentation. Using a stainless steel fermentor, batches can be harvested every third day, meaning a maximum of 100 batches can be produced per year at 100% utilization. However, single-use fermentation batches – which take 33% less time to complete – can be harvested every second day, giving a maximum of 150 batches per year. The difference was particularly marked in the multi-product scenario.
Cleaning validation downtime
When stainless steel equipment is used, the final equipment CIP procedure at the end of each campaign is followed by cleaning validation. This procedure can take seven days, but it’s significantly reduced or eliminated altogether when producing in a single-use fermentor. Futhermore, the risk for product carry-over from production vessels is non-existent with single-use equipment, meaning new campaigns can be started faster.
Higher costs for consumables
When it comes to cost, the picture is more complex. The costs for consumables, such as disposable fermentor bags, were higher in the single-use scenarios. This pushed up single-use costs per batch 29% higher than stainless steel in the single-product facility, and 25% higher in the multi-product facility. However, captial investment, qualification costs, and annual maintenance costs are higher for stainless steel equipment.
This makes the most difference at lower utilization rates, as maintenance costs for stainless steel remain constant regardless of equipment utilization. And in certain situations–for example, a manufacturing start-up or small volume vaccine production–the utilization rate might be very low.
Faster to market?
In process development, the shorter process time that comes with single-use equipment can lead to decreased development time overall. And, that can have a positive impact on market access as well as finances.
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