Preparation of N-acetylneuraminic acid from delipidated egg yolk.

Egg yolk, a large proportion of the egg, was studied for the preparation of N-acetylneuraminic acid (Neu5Ac). The delipidated hen egg yolk (DEY; 500 kg containing 0.2% w/w, Neu5Ac) was hydrolysed with HCl (pH 1.4) at 80 degrees C and neutralized with NaOH (pH 6.0). The mixture was filtered and electrodialysed until the conductivity was 240 microS cm-1. The filtrate was applied on a column of Dowex HCR-W2 (20-50 mesh), followed by a column of Dowex 1-X8 (200-400 mesh). The latter column was washed with water, and then eluted with a linear gradient of HCO2H (0-2 M). The eluates containing Neu5Ac were concentrated using a reverse osmosis membrane and, finally, rotary evaporated at 40 degrees C. The residue was then lyophilized to yield 500 g Neu5Ac. The purity of Neu5Ac was > 98% (TBA method). HPLC, NMR spectroscopy and TLC chromatography of the product obtained from the DEY showed that Neu5Ac was the sole derivative present in egg yolk. The DEY, a byproduct from egg processing plants, was found to be an excellent source for the large-scale preparation of Neu5Ac.