EXTREMELY THERMOPHILIC CELLULOLYTIC ANAEROBES FROM ICELANDIC HOT-SPRINGS

Anaerobic enrichment cultures with Avicel as substrate and inoculated with biomat samples from Icelandic hot springs were cultured at 70 deg rees C or 78 degrees C and examined for the presence of microorganisms that produce extracellular cellulolytic and xylanolytic enzymes. From four enrichments grown at 78 degrees C eighteen strains were isolated . Five of the strains were screened for their substrate utilization, a nd on the basis of differences in morphology and substrates used, the two most unique strains were selected for further characterization. Al l cellulolytic cultures were rod-shaped and non-sporeforming. Motility was not observed. Cells stained gram-negative at various stages of th e growth phase. During growth on Avicel, most cultures produced acetat e as the major fermentation product, with smaller amounts of lactic ac id and ethanol. Carbon dioxide and hydrogen were also produced. The ph enotypic characteristics of the enrichment cultures and of isolates ar e described and assessed in relation to temperature and pH in the hot spring environment. A comparison is made between Icelandic strains iso lated in our laboratory and strains isolated from hot springs from oth er parts of the world. The biotechnological potential of this group of bacteria is briefly discussed.