Asahi Kasei’s BioOptimal MF-SL filters offer a filtration performance which results in faster processing times and higher-quality protein streams, even when filtering high-density cell culture solutions. The unique hollow-fibre membrane structure used in BioOptimal MF-SL filters enables gentle processing of cells and proteins in tangential flow mode, which reduces the burden on subsequent processing steps. This also makes BioOptimal MF-SL filters suitable for use in perfusion-based fermentation processes.