BIOPROCESSWATCH

In the realm of biopharmaceutical production, Chinese Hamster Ovary (CHO) cells have emerged as the main expression system for recombinant therapeutic proteins (RTPs), despite the availability of several alternative cell lines. CHO cells are among the most widely used worldwide for their unique advantages, e.g, the variety of post-translational modifications that closely mimic those found on human cells (Stach et al. 2019); their high degree of biosafety due to their low risk of propagation of human viruses infection (Lalonde and Durocher, 2017); their adaptability from adherent to suspension cell culture in serum-free media (Davami et al. 2014). Thanks to these combined attributes that solidified the position of CHO cells, they have become the gold-standard of the bioindustry and are responsible for the production of approximately 70% of all marketed RTPs (Pereira et al., 2018; Stolfa et al., 2018; Dziomba et al. 2023).

Fetal bovine serum (FBS) is commonly used as a supplement to basal media for in vitro cell cultures (including mammalian, animal, insect, and bacterial cells). Many studies have revealed its rich composition, containing essential macro- and micronutrients such as growth factors, adherent factors, amino acids, hormones, and vitamins (Michael Butler et al. 2020), which are crucial for proper cell function. In addition to the ethical issue, increasing demand, high cost, significant contamination risks (bacterial and viral), and batch-to-batch variability of FBS prompt us to seek alternatives. To reduce or eliminate FBS use, we have decided to implement culture media with various plant protein hydrolysates. Although serum-free media have been available for several decades, and their widespread adoption has increased, despite the fact that their compositions are undefined for users. Our goal is to make these serum-free media more accessible considering that serum-free media cost about 1.5 to 3 times more than serum-containing media.

Several publications highlighted the effects of vegetable proteins hydrolysate (peptones) as supplements in basal media, i.e : the enhancing of the cell growth and productivity of recombinant proteins (Burteau et al. 2003; Michael J. Betenbaugh et al. 2020). Some publications have shown an enhancing of the volumetric productivity more than 100%, and a 40% increase in cell number (Davami et al. 2014; Davami et al. 2015). Then, the composition of these plant hydrolysates varies according to the plant source and the production process. Thanks to their vegetable origins there are neither ethical issues, nor health standards.

In the present study, the effect of different peptone concentrations on the CHO-K1 cell line under various culture conditions (adherent/suspension) in a basal medium with a 10-fold reduction of FBS have been evaluated. Supplementation with wheat peptones at defined concentrations increased the viable cell density of CHO-K1 in adherent conditions by 190 – 265%.

Additionally, the suspension culture exhibited different results compared to the adherent conditions. In suspension cell culture, only three peptones – wheat, soy, and pea – enhanced viable cell density compared to the medium without hydrolysates. Actually, the only peptone supplementation is not enough to be completely serum-free, but that can reduce the FBS consumption.