Clostridium methoxybenzovorans sp. nov., a new aromatic o-demethylating homoacetogen from an olive mill wastewater treatment digester.

A strictly anaerobic, spore-forming bacterium (3.0-5.0 x 0.4-0.8 microns), designated strain SR3T (T = type strain), which stained Gram-positive and possessed a Gram-positive type cell wall was isolated from a methanogenic pilot-scale digester fed with olive mill wastewater (Sfax, Tunisia). It utilized a number of carbohydrates (glucose, fructose, sorbose, galactose, myo-inositol, sucrose, lactose, cellobiose), organic compounds (lactate, betaine, sarcosine, dimethylglycine, methanethiol, dimethylsulfide), alcohol (methanol) and all methoxylated aromatic compounds only in the presence of yeast extract (0.1%). The end products from carbohydrate fermentation were H2, CO2, formate, acetate and ethanol, that from lactate was methanol, those from methoxylated aromatics were acetate and butyrate, and that from betaine, sarcosine, dimethylglycine, methanethiol and dimethylsulfide was only acetate. Strain SR3T was non-motile, had a G+C content of 44 mol% and grew optimally at 37 degrees C and pH 7.4 on a glucose-containing medium. Phylogenetically, the closest relatives of strain SR3T were the non-methoxylated aromatic-degrading Clostridium xylanolyticum, Clostridium aerotolerans, Clostridium sphenoides and Clostridium celerecrescens (mean similarity of 98%). On the basis of the phenotypic, genotypic and phylogenetic characteristics of the isolate, it is proposed to designate strain SR3T as Clostridium methoxybenzovorans sp. nov. The type strain is SR3T (= DSM 12182T).