β crustacyanin isolated from white leg shrimp (Litopenaeus vannamei) shell by pH-shift processing

We analyzed the effect of pH-shift processing method on isolation of β crustacyanin from white leg shrimp (Litopenaeus vannamei) shell. The recovery rate, purity and secondary structure content of protein were selected as separation characteristics; the protein was recovered by pH-shifting at a 1.0 interval via acid and alkali. Under these conditions, the protein recovery rate reached 47.5% with purity of 78.23%;the molecular weight was 45 000 Da analyzed by SDS-PAGE and Size Exclusion Chromatography; the maximum and minimum solubilities were obtained at pH 3.0 (60.5%), 11.0 (55.7%) and 5.0 (15.4%), respectively; the iso-electric point determined by Isoelectric Focusing Electrophoresis was about 5.6. Secondary structure content obtained by circular dichroism spectroscopy and spectrum revealed that β crustacyanin mainly existed in α helix form and contained nearly 70.1% α helices via pH-shift processing.