NEW MATERIAL:The antibacterial protein having the following characteristics: molecular weight, 4,000W7,500; thermal stability, stable at 100°C for 10W60min; solubility, soluble in hydrous methanol; antibacterial activity, active even in 10% bovine serum medium; amino acid composition (mol%), shown in table I.

USE: Edible antibacterial agent.

PROCESS: The body, usually the part other than the head, of the larva of an insect belonging to Hymenoptera or Diptera (e.g. Sarcophaga peregrina) is incised, and 0W5 days after that, the body fluid is squeezed out, centrifuged to remove the body fluid cells, heated on a water bath to remove lipids and unnecessary proteins from the resultant supernatant liquid, and centrifuged to obtain supernatant liquid to be used as the starting material. The material is purified by ion exchange resin treatment and the thermal treatment keeping all the active components in the material, concentrated by ultrafiltration, and further purified by gel-filtration and ion exchange resin treatment to obtain the objective antibacterial proteins.