Shaft-Mounted Fluid Transfer Assembly for Disposable Bioreactors
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Solution Overview
Problem
Existing bioreactors face challenges in efficiently delivering sparge gas and feed fluids directly below the impeller blades in microbial systems, where microbial cells tend to clump and require high oxygen consumption, and lack a shaft-mounted fluid transfer device that can function as both a sparger and perfusion device for disposable bioreactors.
Innovation Solution
A shaft-mounted fluid transfer assembly with a rotatably-mounted fluid transfer housing that allows for the direct delivery of gases and liquids under the impeller blades, utilizing a rolling element bearing to enable high-speed rotation and prolonged operation, and can be used as a perfusion device by connecting to a port on the bioreactor wall through an elongate conduit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a bottom tethered sparger mechanism is used to deliver sparge gas close to the impeller, then oxygen supply to microbial cells is improved, but the sparger structure adds rigidity to the flexible bioreactor bag and complicates fabrication/assembly
Solution Approach 1:
The patent combines the sparger function with the impeller shaft by mounting the sparger assembly directly to the shaft. This integration eliminates the need for separate bottom tethered sparger structures, simplifying fabrication and assembly while maintaining effective oxygen delivery close to the impeller blades.
Solution Approach 2:
The impeller shaft is designed to serve multiple functions: it provides mechanical agitation through impeller rotation and simultaneously serves as a mounting structure for the sparger assembly. This multi-functionality reduces the number of separate components needed, easing manufacturing and assembly processes.
2Quantity of substance
If a bottom tethered sparger is positioned below the lowest Rushton impeller, then sparge gas delivery is effective, but the position of the sparger with respect to the impeller varies and fabrication becomes more difficult
Solution Approach 1:
By integrating the sparger assembly onto the impeller shaft, the patent eliminates the need for complex bottom tethered structures. The sparger position is determined by the shaft geometry, ensuring consistent positioning relative to the impeller without requiring additional structural elements.
Solution Approach 2:
The sparger assembly mounted on the rotating shaft moves dynamically with the impeller rotation, maintaining optimal positioning throughout the mixing cycle. This dynamic mounting approach simplifies the static structural requirements compared to fixed bottom tethered designs.
3Stability of the object's composition
If high speed impellers are used to break apart microbial cell clumps, then cell mixing is improved, but the requirement for large amounts of air increases oxygen consumption rates
Solution Approach 1:
The sparger assembly is positioned locally at the impeller tips where shear forces are highest, delivering oxygen directly to the regions of greatest cell disruption. This localized oxygen delivery optimizes the balance between cell mixing and oxygen supply, addressing the increased oxygen demand in high-speed mixing conditions.
Solution Approach 2:
The sparger delivers oxygen to the culture before and during the high-speed impeller action that breaks cell clumps. This preliminary oxygen supply ensures that oxygen is available in advance of the intensive mixing event, supporting the high oxygen consumption rates that result from rapid cell multiplication.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures precise delivery of oxygen and fluids directly under the impeller blades, effectively breaking up cell clumps and supporting rapid microbial growth, while allowing for independent rotation of the impeller shaft and flexible installation along the impeller shaft, enhancing mixing and oxygen supply in microbial fermentation processes.
Implementation Method 1
utilizing a rolling element bearing to enable high-speed rotation and prolonged operation
Implementation Method 2
Microbial cells have protective cell walls, and tend to clump together when grown in a bioreactor. Microbial cell cultures thus require high speed, shearing impellers to break apart the clumps of cells
Implementation Method 3
In microbial bioreactors, sparge gas needs to be applied in close proximity to the lowest impeller, preferably directly under the lowest Rushton impeller
Data Source
AI summary
A fluid transfer assembly for single use bioreactors includes a fluid transfer housing that can be mounted to the impeller shaft using a bearing that places the fluid transfer assembly directly below the lowest impeller but allows the impeller shaft to spin inside independently of the fluid transfer assembly. A fluid conduit connects the fluid transfer housing to a port in the single use bag wall which allows fluids to be introduced into the sparger and which also helps prevent the fluid transfer assembly from rotating with the impeller shaft.