Plasticicumulans lactativorans sp nov., a polyhydroxybutyrate-accumulating gammaproteobacterium from a sequencing-batch bioreactor fed with lactate

A bacterial consortium that accumulated more than 90% (w/w) polyhydroxybutyrate (PHB) from lactate was selected in a laboratory-scale bioreactor with a 'feast-famine' regime. Bacterial strain YDT, representing a dominant species in this enrichment, was isolated and characterized. Analysis of the 16S rRNA gene sequence revealed that the isolate is a member of the class Gammaproteobacteria, forming an independent phylogenetic lineage. The closest relative of the isolate was Plasticicumulans acidivorans TUD-YJ37(T), with 94% 16S rRNA gene sequence similarity. Strain YDT was an obligate aerobe with large, ovoid, Gram-negative cells, motile by means of a polar flagellum. It utilized a relatively broad spectrum of substrates (e.g. carbohydrates, fatty acids) as carbon and energy sources. The temperature range for growth was 20-45 degrees C, with an optimum at 40 degrees C; the pH range was pH 6.0-8.0, with an optimum at pH 7.0. The major respiratory lipoquinones were Q-8 (91%) and Q-7 (9%). The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmono-methylethanolamine and an unidentified aminolipid. The predominant fatty acids in the membrane polar lipids were C-16:1 omega 7c, C-16:0 and C-18:1 omega 7c. The G+C content of the genomic DNA was 68.5 mol%. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, the isolate is proposed to represent a novel species in the genus Plasticicumulans, for which the name Plasticicumulans lactativorans sp. nov. is proposed. The type strain is YDT (=DSM 25287(T)=NCCB 100398(T)).