PROTEASES OF PSYCHROTROPHIC BACTERIA ISOLATED FROM GLACIERS

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-degrees-C and pH 7. Enzymes were rapidly inactivated after heating at 50-degrees-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.