Extracellular Protease-producing Psychrotrophic Bacteria from High Alpine Habitats

Abstract

Four hundred and thirty psychrotrophic strains of microorganisms were isolated from high alpine environments of the Western and Eastern Alps in Europe. Of the isolates, 77% were bacteria, 5% among them were actinomycetes. 20% of the isolates were yeasts, and 3% were hyphomycetes. All bacterial strains, with the exception of actinomycetes, were tested for their optimum growth temperature and screened for the production of extracellular proteases. The optimum temperature for growth of the majority of the bacterial strains was within the range of 10 to 25°C. Almost half of the bacterial strains excreted protease into the medium at a cultivation temperature of 10°C. The major part ofcell-free protease-containing culture filtrates showed a maximum caseinolytic activity at pH 7 and 30°C. Sensitivity to EDTA indicates that most bacteria produced metalloproteases. Fifty-four producers ofprotease were selected for taxonomic characterization. The genus Pseudomonas, especially the species P.jluorescens and P. paucimobilis, was found to be dominating.