Clarification of fermentation broths is one of the most important steps in bioprocessing. The first purification step after fermentation is the cell harvest, which is designed to remove cells and cell debris as well as to reach maximum product yield in compliance with existing regulatory environments. Standard technologies (centrifugation, separators, membrane, and depth filtration) can no longer handle the high particle loads (>108 cells/mL) in an economical way.
Deciding on the right purification system involves addressing questions about process performance, economics, and existing regulatory requirements. Process performance challenges include higher and higher cell titers, cell debris content, scalability, and flexibility for process changes and future processes, higher product yields, and constant high-quality product flow for further downstream purification.
Alluvial filtration (see box below) is a well-established and economical method in pharmaceutical industries (plasma fractionation). Use of a filter aid such as diatomaceous earth (DE) provides a large capacity for high particle loads, which corresponds to dramatically extended filtration volumes per filter area (up to 80%).