ISOLATION OF COPROTHERMOBACTER-PROTEOLYTICUS FROM AN ANAEROBIC DIGEST AND FURTHER CHARACTERIZATION OF THE SPECIES

Anaerobic, thermophilic, proteolytic strains were isolated from biokitchen waste digested by a Dry Anaerobic Composting process (DRANCO) under thermophilic conditions (55 degrees C). The cellular and physiological properties of one representative isolate (strain I8 = LMG 14268) were further investigated. The cells were gram-negative, nonsporeforming, nonmotile rods. The deoxyribonucleic acid base composition was 43.5 mol% guanine-plus-cytosine. The optimal pH and temperature for growth were 6.8-7.4 and 65-70 degrees C. Based on phenotypic, chemotaxonomic and genotypic properties strain I8 was identified as Coprothermobacter proteolyticus and this species was characterized in more detail. The major cellular fatty acids comprised C-15:0 iso, C-16:0, C-14:0 iso 3OH, C-17:0 iso and a fatty acid with an equivalent chain length of 15.360. C. proteolyticus I8 exhibited extracellular protease activity and fermented a variety of proteinaceous substrates with acetate as major end product. C. proteolyticus grew also on various carbohydrates. Growth of the organism was effectively inhibited by neomycin, penicillin G and 0.7 M Na+ Significant differences were observed between C. proteolyticus and the type strain of Thermobacteroides leptospartum. An emended description of Coprothermobacter proteolyticus is given.