Studies on the Proteolytic Action of Dairy Lactic Acid Bacteria

Abstract

Intracellular protease (IPLB) of Streptococcus cremoris was extracted from the cells, which were cultivated in liquid media, by momentarily disrupting between two disks by high pressure.The hydrolyzing modes of αs-, crude k-, β-, and whole casein by IPLB of Str. cremoris or rennet were observed through the released amounts of tyrosine, sialic acid, NPN, and calcium insensitive substance. Relative specific turbidity of casein solution and dissymmetry coefficient of casein were measured. Particle weight and UV absorption spectrum of each high molecular hydrolyzate of whole casein were also determined.Among four kinds of casein fractions, αs- or crude k-casein was most easily hydrolyzed by IPLB of Str. cremoris or rennet. Relative specific turbidity of crude k-casein solution was remarkably, but those of αs-, β-, and whole casein slightly increased by the action of IPLB of Str. cremoris or of rennet. Changes of dissymmetry coefficients were negligibly induced by these two enzymes. Absorption spectrum of IPLB...