| Accumulation of polyhydroxyalkanoates by Microlunatus phosphovorus under various growth conditions.
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Akar A.,Akkaya EU.,Yesiladali SK.,Celikyilmaz G.,Cokgor EU.,Tamerler C.,Orhon D.,Cakar ZP.
J. Ind. Microbiol. Biotechnol. 33 (2006) 215-20 [PMID: 15660231] Abstract
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| Abstract: Microlunatus phosphovorus is an activated-sludge bacterium with high levels of phosphorus-accumulating activity and phosphate uptake and release activities. Thus, it is an interesting model organism to study biological phosphorus removal. However, there are no studies demonstrating the polyhydroxyalkanoate (PHA) storage capability of M. phosphovorus, which is surprising for a polyphosphate-accumulating organism. This study investigates in detail the PHA storage behavior of M. phosphovorus under different growth conditions and using different carbon sources. Pure culture studies in batch-growth systems were conducted in shake-flasks and in a bioreactor, using chemically defined growth media with glucose as the sole carbon source. A batch-growth system with anaerobic-aerobic cycles and varying concentrations of glucose or acetate as the sole carbon source, similar to enhanced biological phosphorus removal processes, was also employed. The results of this study demonstrate for the first time that M. phosphovorus produces significant amounts of PHAs under various growth conditions and with different carbon sources. When the PHA productions of all cultivations were compared, poly(3-hydroxybutyrate) (PHB), the major PHA polymer, was produced at about 20-30% of the cellular dry weight. The highest PHB production was observed as 1,421 mg/l in batch-growth systems with anaerobic-aerobic cycles and at 4 g/l initial glucose concentration. In light of these key results regarding the growth physiology and PHA-production capability of M. phosphovorus, it can be concluded that this organism could be a good candidate for microbial PHA production because of its advantages of easy growth, high biomass and PHB yield on substrate and no significant production of fermentative byproducts. |
| Microlunatus phosphovorus gen. nov., sp. nov., a new gram-positive polyphosphate-accumulating bacterium isolated from activated sludge.
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Nakamura K.,Hiraishi A.,Yoshimi Y.,Kawaharasaki M.,Masuda K.,Kamagata Y.
Int. J. Syst. Bacteriol. 45 (1995) 17-22 [PMID: 7857797] Abstract
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| Abstract: Polyphosphate-accumulating bacteria that were previously isolated from activated sludge and exhibited high phosphate removal activity were studied taxonomically and phylogenetically. These organisms were gram-positive, coccus-shaped, aerobic chemoorganotrophs that had a strictly respiratory type of metabolism in which oxygen was a terminal electron acceptor. They accumulated large amounts of polyphosphate under aerobic conditions. The major quinone was menaquinone MK-9(H4). The cell wall peptidoglycan contained LL-diaminopimelic acid. The guanine-plus-cytosine content of the DNA was 67.9 mol%. Our isolates were similar phenotypically and chemotaxonomically to Luteococcus japonicus, which was proposed recently as a new genus and species. However, our isolates differed from L. japonicus in cellular fatty acid composition and some other traits. A phylogenetic analysis based on 16S rRNA sequences showed that our isolate differ from the genus Luteococcus and other genera belonging to the high-G+C-content gram-positive group. Accordingly, we concluded that our strain NM-1T (T = type strain) should be assigned to a new genus and species, for which we propose the name Microlunatus phosphovorus. |
