Effect of partial medium replacement on cell growth and protein production for the high-five™ insect cell line

The potential of spent medium to support the growth and recombinant protein production of High-Five™ cells was investigated. Growth in medium consisting of three parts fresh and one part spent medium was comparable to that in fresh medium (maximal specific growth rates of 0.028 and 0.029 h ^-1, and maximal cell densities of 4 and 4.5 × 10 ⁶ cells ml ^-1, respectively). Glucose exhaustion coincided with an abrupt decrease of viability. Of 15 amino acids analyzed, not a single one was completely exhausted at the end of the growth phase. Growth in medium consisting of equal parts spent and fresh medium led to lower maximal cell concentration (2.9 × 10 ⁶ cells ml ^-1) with a smoother death phase. Glucose supplementation at the beginning of the culture or at the end of the growth phase did not lead to an increase of either the maximal cell density or the specific growth rate. Infection of High-Five™ cells at three different densities (1.4, 2.5 and 4.2 × 10 ⁶ cells ml ^-1) without medium change led to monotonically decreased specific productions for β-galactosidase. Partial (75%) or total medium replacement at the higher infection density restored the specific production at the levels of the intermediate density infection (321, 292 and 389 U.(10 ⁶ cells) ^-1, respectively).