Utilization of tyrosine- and histidine-containing dipeptides to enhance productivity and culture viability

Adequate supply of nutrients, especially providing a sufficient level of specific amino acids, is essential for cell survival and production. Complex raw materials such as soy hydrolysates or yeast extracts are the source for both free amino acids and peptides. However, typical chemically defined (CD) media provide amino acids only in free form. While most amino acids are highly soluble in media and can be provided at fairly high concentrations, certain amino acids such as tyrosine have poor solubility and thus, only a limited amount can be added as a media component. The limited solubility of amino acids in media can raise the risk of media precipitation and instability, and could contribute to suboptimal culture performance due to insufficient nutrient levels to meet cellular demands. In this study, we examine the use of chemically synthesized dipeptides as an alternative method for delivering amino acids to various monoclonal antibody producing cell lines. In particular, we focus on tyrosine-containing dipeptides. Due to their substantially higher solubility (up to 250-fold as compared with free tyrosine), tyrosine-containing dipeptides can efficiently provide large amounts of tyrosine to cultured cells. When tested in fed-batch processes, these supplemental dipeptides exerted positive effects, including enhanced culture viability and titer. Moreover, dipeptide-supplemented cultures displayed improved metabolic profiles including lower lactate and NH 4(+) production, and better pH maintenance. In bioreactor studies using two-sided pH control, a lactate spike occurring on Day 10 and the concomitant high levels of base addition could be prevented with dipeptide supplementation. These beneficial effects could be obtained by one-time addition of dipeptides during inoculation, and did not require further feeds during the entire 11-15-day process. Non-tyrosine-containing dipeptides, such as His-Gly, also showed improved productivity and viability over control cultures.