Combining mixing and grinding for Cell Culture Media

Over the past 20 years, Hosokawa has developed the expertise to provide integrated solutions for producing dry powder cell culture media, from a full-blown closed loop inert system that starts with pre-mixing, milling, post-mixing and ending with containment free packaging to basic gravity feed and discharge size reduction systems.

Cell culture is the process by which cells are grown under controlled conditions, generally outside their natural environment. The base for optimal cell activity and growth curves lies in the recipe and the correct formulation of the contents.

When the right mixture is found, a validated production line with reproducible, high-quality media plays a decisive role. The dry medium must be homogeneous, both in particle size and mixing ratio, in order to not only dissolve quickly but also to ensure the same and correct composition in every single dose. The production systems used must be flexible and efficient if new batches, with different recipes, are to be produced every day. Quick, automatic and validated wet cleaning and drying of the production line is essential for the production of high quality media.

Production of cell culture media

The challenge for producing cell culture media lies in the almost limitless number of recipes with lots of different components, with its different bulk density, particle size, flowability etc. This requires an universal system in which the following process steps are recognized:

Formulation » Pre-mixing » Grinding » Post-mixing » Packaging

The Hosokawa system immediately starts after the formulation in which the proven core technologies mixing and grinding are integrated in a seamless process for a high grade media quality.

After formulation, the materials are charged in the pre-mixer. The material is mixed and the homogenized material is dosed into the UPZ fine impact mill, which can be mounted on the post-mixer. The ground material is collected in the post-mixer where if needed additional materials can be added. After another homogenization step, the end product is packed in the contamination-free packing unit.

UPZ mill, mounted on Nauta mixer

This vertical design offer great flexibility for a wide range of formulations with:

  • A closed loop inert system
  • Temperature controlled milling (down to -40°C)
  • High mixing accuracy
  • Contained packaging
  • Integrated cleaning

Mixing

Hosokawa Micron's Nauta® conical screw mixer is a convective mixer with high mixing efficiency. It is gentle and guarantees the highest level of mixing accuracy without product distortion. The cantilevered mixing screw is suspended from an orbital arm, which rotates the screw along the conical inner vessel wall, causing convective mixing of particles and shear.

Convective mixing effect of a Nauta mixer

To avoid cross-contamination between batches, these mixers are designed to cGMP sanitary standard, with a semi- or fully domed cover (welded to the vessel in one piece), purged seals and a special internal finish. Removable or fixed spray balls are mounted for cleaning the interior of the mixer. The location of the sprayers is carefully chosen to wet all interior surfaces, including the nozzles.

Decisive advantages of the Nauta mixer:

  • Highest mixing accuracy
  • Gentle mixing without product distortion
  • Flexible batch sizes from 15 up to 100%
  • Sanitary design for excellent cleaning
  • No segregation during discharge

Milling

Hosokawa Alpine's UPZ fine impact mill is used for fine and ultrafine grinding. Generally, it covers a range of approximately 20 to 1500 μm. A wide variety of grinding inserts are available for this kind of mill, enabling a high flexibility regarding products and achieved particle sizes. The rotor's ventilation effect provides a cool milling process and an end product low in fines, with good flowability.

In cell culture media preparation, the UPZ mill is usually equipped with pin discs for very fine and homogenous products up to 90% < 20 - 150 μm. Milled products have a 'steep' particle size distribution and can be mixed easily. For special cell culture media formulation, the Alpine Contraplex pin mill can be applied, with counter-rotating pin discs and the option for cryogenic milling with LN2 cooling (down to -40 °C).

The mills are designed to cGMP standards and comply with the highest hygienic regulations. They can be provided with automated WIP systems. Characteristic features are maximum product recovery and optimum cleanability.

Decisive advantages of the Alpine fine impact mill:

  • Steep particle size distribution
  • Low temperature milling
  • Sanitary design for excellent cleaning

Cleaning

Cell culture media production systems must be flexible and efficient when new batches with different recipes have to be produced every day. Cleanability is therefore an essential aspect when selecting the right process equipment. Hosokawa mixers and mills are designed to avoid contamination. The vertical aseptic design, with a high grade surface finish and the conical mixer vessels with the fixed connection to the mill offer maximum product recovery.

However, even with all measures taken, some contamination cannot be avoided. For wet cleaning the production line, spray nozzles are positioned on strategic positions to wet all internals, ensuring a thorough top-down cleaning. The spray nozzles clean the surfaces by a combination of impact and solution. Starting by cleaning the pre-mixer, through the mill, the post-mixer and finally the packaging unit. After wet cleaning, hot air is used to dry all internals from bottom to top, using the chimney effect.

This proven Hosokawa design offers quick and validated wet cleaning and drying of a cell culture media production line.

Automation

The production line is controlled by a fully automized control system, compliant with the highest pharmaceutical standards, such as FDA, cGMP and GAMP.

Key features:

  • Core processes of mixing and grinding from one single source
  • Cooled fine grinding with the Alpine fine impact mill
  • Gentle but simultaneously intensive mixing in the conical Nauta mixer
  • Integrated, automatic system cleaning
  • Maximum degree of automation