Proteases of psychrotrophic bacteria isolated from glaciers

Abstract 25 psychrotrophic protease‐forming bacteria isolated from glaciers were identified as follows: Pseudomonas spp. (18 strains), Flavobacterium spp. (3 strains), Xanthomonas maltophilia (2 strains), Aeromonas hydrophila (1 strain) and Bacillus sp. (1 strain). Characteristics of proteolytic activity in cell‐free culture supernatants were studied. Proteases produced by 40% of the bacteria showed a maximum azocaseinolytic activity around 40°C and pH 7. Enzymes were rapidly inactivated after heating at 50°C. pI‐values of proteases ranged from > 9.5 to 7.0. Sensitivity to EDTA indicates that most proteases are metalloproteases. Proteases of psychrotrophs could be differentiated from proteases of mesophiles by a lower temperature optimum, a lower activation energy and a higher sensitivity against heat treatment.