Two proteolytic, strictly anaerobic bacterial strains (TB107T and TB6-6) were isolated from the granule sludge of an upflow anaerobic sludge blanket reactor treating brewery wastewater. The strains were Gram-negative, non-spore-forming and motile. Cells were rod-shaped (0·6–0·9×1·9–2·2 μm). Growth of the strains was observed at 20–45 °C and pH 6·0–9·7. The strains were proteolytic. Yeast extract, peptone, pyruvate, glycine and l-arginine could be used as carbon and energy sources. Weak growth was also observed with tryptone, l-serine, l-threonine and l-alanine as carbon and energy sources. Both strains did not use any of the tested carbohydrates, alcohols and fatty acids except pyruvate. Acetic acid and NH3 were produced from yeast extract, peptone and l-arginine, and propionic acid was also produced from yeast extract. Pyruvate was converted to acetic acid and CO2. Gelatin was not hydrolysed. Indole and H2S were not produced. The two strains did not grow in medium containing 20 % bile. Addition of strain TB107T to a syntrophic propionate-degrading co-culture accelerated the propionate-degradation rate. The predominant cellular fatty acid was the branched-chain fatty acid anteiso-C15 : 0 (46·21 %). The genomic DNA G+C contents of strains TB107T and TB6-6 were 46·6 and 48·9 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the two strains represent a new phyletic sublineage within the Cytophaga–Flavobacterium–Bacteroides (CFB) group, with <91 % 16S rRNA gene sequence similarity to the closest species with validly published names. On the basis of polyphasic evidence from this study, a new genus and species, Proteiniphilum acetatigenes gen. nov., sp. nov., is proposed, with strain TB107T (=JCM 12891T=AS 1.5024T) as the type strain.

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A spore-forming anaerobic bacterium, designated strain P6T, was isolated from the sludge of an up-flow anaerobic sludge blanket reactor treating brewery wastewater. Cells were Gram-positive, oval and 0.6–0.9 μm by 1.2–1.8 μm in size. Growth was observed at 20–42 °C and at pH 5.0–7.5. It fermented several hexoses, polysaccharides and alcohols. Sucrose and aesculin could also be fermented. The main end products of fermentation from glucose were acetate, lactate and fumarate; trace CO2 and H2 were also produced. The DNA G+C content of strain P6T was 55.6 mol%. The major cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0 and iso-C14 : 0 3-OH. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain P6T represented a novel phyletic sublineage in clostridial cluster III, and showed <91 % similarity to the type strains of recognized species in this cluster. Phenotypically, the new isolate was distinguished from its phylogenetic relatives (e.g. Clostridium straminisolvens, Clostridium thermocellum, Acetivibrio cellulolyticus and Clostridium aldrichii) by producing acid from glucose and its inability to degrade cellulose. On the basis of evidence from this polyphasic study, strain P6T is considered to represent a novel species of a new genus, for which the name Saccharofermentans acetigenes gen. nov., sp. nov. is proposed. The type strain of Saccharofermentans acetigenes is P6T (=JCM 14006T =AS 1.5064T).