Isolation and characterization of two glycerol-fermenting clostridial strains from a pilot scale anaerobic digester treating high lipid-content slaughterhouse waste

Two obligately anaerobic bacterial strains were isolated from the contents of a pilot scale, anaerobic digester treating slaughterhouse waste with a h igh protein and lipid content. The isolates, LIPI and MW8, were characteriz ed as spore-forming, Gram-positive rods, capable of fermenting glycerol, Is olate LIP1 was also observed to be lipolytic and was able to hydrolyse tall ow and olive oil. Both isolates grew optimally at 37 degrees C and formed e ither acetate and formate (LIP1), or acetate and butyrate (MW8), as major g lycerol fermentation products, Both isolates produced ethanol as the major reduced fermentation end-product, Neither MW8 nor LIP1 had growth and metab olism inhibited by the addition of stearic acid at concentrations normally considered bactericidal. Analysis of the 16S rRNA gene sequences, in conjun ction with the phenotypic data, confirmed that the isolates are members of the genus Clostridium (sensu Into), clustering with species of clostridial clusters I (MW8) and XIVa (LIP1).