S116: HIgher Density Fed-Batch Culture through Elimination of Lactic Acid Production

In 2009, we introduced a novel strategy to reduce lactic acid production and control pH in animal cell culture.  This successful strategy involves: 1) supplementing the medium with sufficient lactate to eliminate the net flux of pyruvate to lactate, and 2) adapting the cells to grow well in this high level of lactate.  In 2010, we applied our novel technology to the development of higher density, fed-batch CHO cell cultures in pH-controlled bioreactors.  For a blank CHO cell line (DG44), this approach successfully reduced lactic acid production and base additions by eight fold and allowed more concentrated nutrient feeds to be added without excessive increases in osmolality. Viable cell densities of 35 million cells per ml were achieved, among the highest ever reported for a fed-batch animal cell culture.  Furthermore, high viabilities were maintained for an extended period, resulting in an integral viable cell day (IVCD) level of 273 million cell-days per ml, again among the highest ever reported for a fed-batch animal cell culture.   In 2010 and 2011, we tested this technology for two CHO cell lines engineered to make recombinant products, as well as a different blank CHO line (CHO-S).  The technology again proved effective.  Certain other operating conditions, such as the basal medium formulation, feed formulations, and operating conditions, needed to be optimized for these different cell lines.