[Isolation, identification and phylogenetic analysis of a thermophilic cellulolytic anaerobic bacterium]

Four strains of thermophilic cellulolytic anaeobic bacteria were isolated from fresh feces, heat compost, cellulolytic mixed culture with a method based on adherence of cellulolytic bacteria to cellulose. The cells of isolates were straight or slightly curved rods that were 0.4 micron-0.6 micron x 3 microns-15 microns, Gram negative, strictly anaerobic, sulfate reduction negative, spore-forming bacteria. Most of the cells had oval terminal spores, while subterminal spores, middle spores, two or more spores also could be observed and spore formation could occurred in any position. The isolates degraded cellulose filter paper, cellulose powder Whatman CF II, microcrystalline cellulose, cellulose powder MN300 and unpretreated maize stem core, sugarcane residue and rice straw. The pH and temperature ranges for growth on cellulose were 6.2-8.9 and 45 degrees C-65 degrees C respectively with the optima, 7.0-7.5 and 55 degrees C-60 degrees C, respectively. The major fermentation products from cellulose were acetic acid, ethanol, CO2, H2. The isolates could ferment cellobiose, glucose, fructose, maltose, and sorbital. The phylogenetic analysis based on 16S rDNA suggested strain EVA1 was the closest relative of Clostridium thermocellum with 99.8% sequence similarity.