Detection of peptidoglycan and beta-glucan with silkworm larvae plasma test

A method to detect peptidoglycan and (1-->3) beta-D-glucan with silkworm larvae plasma (SLP) derived from the hemolymph of the silkworm, Bombyx mori was developed. SLP contains all of the factors of the pro-phenol oxidase cascade, an important self-defense mechanism of insects. Peptidoglycan or (1-->3)-beta-D-glucan initiates the cascade, in which pro-phenol oxidase is finally activated to phenol oxidase. The phenol oxidase activity was colorimetrically or visually detected with 3,4-dihydroxyphenylalanine as a substrate. SLP displayed high reactivity with peptidoglycan and polysaccharides containing 1,3-beta-glucosidic linkages, but not with endotoxins. SLP is useful for the detection of microbial contamination because peptidoglycan and (1-->3)-beta-D-glucan are cell wall components of bacteria and fungi, respectively.