Hemolymph (500 lL) was individually withdrawn from the ventral sinus cavity of healthy P. monodon shrimp using a 1-mL syringe containing 500 lL ice-cold anticoagulant solution (0.45 M NaCl, 0.1 M glucose, 26 mM citric acid, 30 mM trisodium citrate, 10 mM EDTA; pH 4.6). Hemocytes were immediately collected by centrifugation at 800g for 10 min at 4 C and the obtained hemocyte pellet was immediately washed twice and homogenized in 100 lL cacodylate buffer (10 mM sodium cacodylate, 10 mM CaCl2; pH 7.0) before being centrifuged at 25,000g for 20 min at 4 C. The shrimp hemocyte lysate supernatant (SHLS) was harvested, adjusted to a protein content of 1 mg/mL and subsequently used as a source of the PO enzyme for preparation of the active melanization reaction products. 2.