(506c) Use of Flocculation to Improve Clarification Efficiency in a Microbial Feedstream

E. coli is one of the fastest growing, least expensive, and highest product-to-volume systems available for the production of therapeutic proteins. Despite these advantages, efficient clarification of the product stream can be challenging due to its high solids content, propensity for cell lysis, as well as high concentrations of impurities such as DNA and host cell protein.  While centrifugation can be used to remove larger particles, such as whole cells, many small particles, such as cell debris and protein DNA complexes, are difficult to sediment.  Depth filtration can be used to remove fine particulates but capacities of the depth filters can be limited, especially by high DNA concentration.   In this presentation, polycation precipitation is explored as a method to enhance the removal of cells, cell debris and DNA during centrifugation processes. Screening is performed using a combination of high throughput methods and bench scale experimentation. We examined the impact of polycations on processability, particle size distribution, DNA and host cell protein content.  Subsequent scale-up work has demonstrated a minimum four-fold increase in depth filter capacity using optimized flocculation conditions.