C10 10

The cryogels are housed in commercial available column hardware as mentioned in the materials section. We used columns from GE Healtcare such as C10/10, XK16/20, XK26/20 or XK50/20. These columns were optimal as they were easy the handle as they had the correct dimensions to prepare columns of different dimensions for chromatographic experiments. The epoxy-phage-cryogels are connected to an Äkta Pure system (GE Healthcare, Uppsala, Sweden) and equilibrated with PBS buffer. Defatted human milk is diluted twice with PBS and is loaded on the column and washed with PBS to remove unbound protein. The column is then eluted with phosphate buffer-1M NaCl pH=7.5 (PB-1M). The eluted protein fractions are pooled for quantification. See table 1 for running parameters. Protein concentration of the pooled PB-1M fraction is determined based on the Folin-Ciocalteus method [15] . The yield is finally expressed as μg bound protein.

Allyl glycidyl ether, iminodiacetic acid and 1,6-diamino hexane were purchased from Sigma-Aldrich (Bornem, Belgium); acrylamide, methylene-bis-acrylamide, TEMED, ammonium persulfate, glutaraldehyde, ethanolamine and iminodiacetic acid (IDA) were from Sigma (St.Louis, Mo); C10/10, XK16/20, XK26/20, XK50/20 columns and Äkta Pure chromatographic system are from GE Healthcare (Uppsala, Sweden); Vernier stainless steel temperature probe and Logger Pro software are from Vernier (Beaverton, OR).