Large Scale Emulsification Process

The greatest challenging on emulsions are the large-scale emulsification process and the possible volumes that can be reached, however in our experience these volumes are unlimited as long as the initial pre-mixture and pre-emulsification process are small and are divided in steps.

Emulsifying large volumes of liquid can be a complex and demands tasks that requires meticulous attention to detail at every stage of the process. In a recent project, we faced the challenge of emulsifying 16,700 liters of oil in a water vaccine, which included a viral antigen as the water phase, 40% mineral oil, and 10% tentative into a 50/50 emulsion. This process requires refrigeration and a viscosity under 200 cps, making it a significant challenge. However, we employed a pre-mixture strategy and “broke” the process into smaller steps, resulting in a successful scale-up and a robust industrial process.

A few considerations are important in this case; reliable equipment with appropriate dimensions and meticulous adjustment and estimations of all small-scale parameters are required for a successful transfer form bench to industrial scale.

In short, the process was developed as the following:

To prepare for the oil phase, we followed a two-stage process. First, we pumped mineral oil into an empty vessel after transferring it from barrels to ensure compliance with GMP. We followed the same procedure for the tensoative to avoid errors during the operation. After that, we mixed both oils vigorously and sterilized the mixture using two 30-inch Pall filters (AB3DFL7PHA). To facilitate the filtration, we pre-warmed the oil mixture to 50-70°C, once filtration was complete, we prepared the water phase.

The water was transferred from disposable begs to an empty vessel and mixed with PBS and other components until full completion (refrigerated at 2-8°C). Once both phases were ready, the PRE-MIXTURE started. This phase consisted of a mixture of oil and water at low speed at a rate of 9 liters per minute, under continuous agitation. The total volume of 16.700 liters was divided in this step in small volumes of 1000 liters. This was a solution encountered to ensure a robust emulsification process.

The emulsion micelle was created by homogenizing the mixture twice using a high-speed colloid mill Silverson Mixer Homogenizer (Silverson). To achieve the optimal particle size for immune system activation, 90% of the emulsion micelle must be smaller than 1 micron. After homogenization, the mixture was transferred to a storage container until the remaining 16,600 liters were added. Once the complete volume was emulsified, an additional emulsification passage was added to the process. This time, the 16,700 liters were passed through Silverson to ensure complete emulsification. The emulsion went through the emulsifier three times in total, and the process was carried out under refrigeration between 2-8°C. It is crucial to maintain this temperature range as the antigen is sensitive to temperature changes, and below there is a schematic of the complete formulation process, from pumping the oil to the vessel until the final emulsification and prefilling.

For a successful process, it is essential to define the appropriate Critical Process Parameters (CPPs) at bench scale and then scale them up to different volumes until optimal results are achieved.

When selecting equipment, it is essential to consider several factors to ensure that you are making an informed decision. Firstly, you need to assess the specific needs of your project or task and determine which equipment is best suited to fulfill those requirements. It is also crucial to evaluate the equipment’s quality, reliability, and durability, as well as its safety features and ease of use. Additionally, you should consider the cost-effectiveness of the equipment and its compatibility with your existing tools and systems. By considering these factors, you can make a more informed decision and choose the right equipment to help you achieve your goals efficiently and effectively.

Below you can find important critical process specification that require attention such as:  

– High-shear colloid homogenizer: This equipment mixes liquids at high shear. It’s crucial to select the right size for the job. For instance, in the process mentioned above, the model 450 was utilized for 16,700 liters.

– Piping: Choosing the correct dimensions for the piping is essential to ensure that the liquid flows through the equipment at the appropriate speed. Selecting the wrong size can result in the liquid passing too quickly or too slowly, causing viscosity issues.

– Vessels: the vessels should be appropriately sized for step-by-step mixing.

– Filters for oil filtration: You can partner with the supplier to find the ideal filter size for your oil filtration requirements. Provide them with a sample of the oil, and they can perform the necessary tests and measurements to provide a complete specification and recommendation. (https://shop.pall.com/de/de/food-beverage/zidAB1FFN7WH4). 

By following these recommendations and appropriately adjusting the scale of your production process, you can establish a robust and reliable method that can be effectively utilized and validated for commercial purposes. Implementing automation for certain steps, such as emulsification, oil filtration, and pre-mixing, can significantly improve the efficiency and precision of the process. As a result, you can achieve better results and ensure consistent product quality.

Schematic of the production flow of the emulsification process