Characteristics of some fermentative bacteria from a thermophilic methane-producing fermenter

Anaerobic bacteria from a 55‡C methane-producing beef waste fermenter were enumerated, isolated, and characterized. Direct microscopic bacterial counts were 5.2-6.8×10(10) per g fermenter effluent. Using a nonselective roll-tube medium which contained 40% fermenter effluent, 8.5-14.1% of the microscopic count was culturable. Deletion of fermenter effluent significantly reduced the viable count. Sixty-four randomly picked strains were characterized. All were pleomorphic, gram-negative, anaerobic rods, many of which were difficult to grow in liquid media. The strains were divided into 5 major groups based on glucose fermentation, hydrogen sulfide production, starch hydrolysis, fermentation products, and morphology. Glucose was fermented by 75% of the isolates, 76% utilized starch, 25% produced hydrogen sulfide, 76% produced hydrogen, 37% produced indole, 21% hydrolyzed gelatin, and 13% were sporeformers. Ethanol, lactate, formate, acetate, and hydrogen were common fermentation products. Twenty-four representative strains had 1-12 flagella. Growth was observed between 35 and 73‡C. These studies indicate that species diversity among the isolated organisms was low.