Feed media

What is this patent about?

’236 is related to the field of cell culture media and methods, specifically focusing on the formulation of concentrated feed media used in large-scale fed-batch cultures of mammalian cells. In the production of therapeutic proteins using cell lines like Chinese Hamster Ovary (CHO) cells, maintaining high nutrient levels is essential for maximizing protein titers. However, concentrated media often suffer from poor solubility and the formation of precipitates during storage, which creates uncertainty in nutrient delivery and complicates regulatory compliance in commercial manufacturing environments.

The underlying idea behind ’236 is that high concentrations of pyruvate can act as a stabilizing agent to prevent the precipitation of poorly soluble amino acids in concentrated cell culture feeds. While amino acids like tyrosine and the oxidized form of cysteine (cystine) are critical for cell growth and protein expression, they have very limited solubility at the near-neutral pH required for biological systems. The inventor discovered that by incorporating specific ranges of sodium pyruvate, these nutrient-dense solutions remain stable and clear for extended periods, even when containing high levels of sulfur-containing amino acids.

The claims of ’236 focus on a method and a resulting composition for a stable, concentrated feed medium containing between 25 mM and 45 mM pyruvate. The independent claims specifically protect formulations where the combined concentration of cysteine and cystine is at least 7.9 mM, while maintaining a pH between 5.8 and 7.4. To ensure stability, the claims also require that the tyrosine concentration is strictly limited—generally to no more than 4.4 mM or 4.6 mM—and include a specific profile of other essential amino acids such as arginine, leucine, and lysine at defined concentration ranges.

In practice, the invention allows for the preparation of a single-part, highly concentrated nutrient feed that can be stored at room temperature or refrigerated at 4–8° C for at least one to three weeks without forming solids. By adding pyruvate, the medium can support much higher levels of cysteine (up to 40 mM) than would otherwise be possible in a stable solution. This concentrated approach is particularly effective for fed-batch bioreactors, as it minimizes the volume of liquid added to the culture, thereby preventing excessive dilution of the produced protein and simplifying large-scale fluid handling.

This approach differs from prior methods that often required heating media to high temperatures to achieve dissolution or maintaining separate, highly alkaline or acidic feed streams to keep specific amino acids in solution. By utilizing pyruvate-mediated stabilization, the invention provides a robust, near-neutral pH solution that is ready for immediate use. This technical insight solves the trade-off between nutrient density and physical stability, ensuring that the precise concentration of components remains known and consistent throughout the duration of a commercial protein production run.