Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Münster, Germany.
J Appl Microbiol. 2010 Nov;109(5):1579-90. doi: 10.1111/j.1365-2672.2010.04786.x. Epub 2010 Jun 24.
This study aimed at isolating thermophilic bacteria that utilize cheap carbon substrates for the economically feasible production of poly(3-hydroxybutyrate), poly(3HB), at elevated temperatures.
Thermophilic bacteria were enriched from an aerobic organic waste treatment plant in Germany, and from hot springs in Egypt. Using the viable colony staining method for hydrophobic cellular inclusions with Nile red in mineral salts medium (MSM) containing different carbon sources, six Gram-negative bacteria were isolated. Under the cultivation conditions used in this study, strains MW9, MW11, MW12, MW13 and MW14 formed stable star-shaped cell-aggregates (SSCAs) during growth; only strain MW10 consisted of free-living rod-shaped cells. The phylogenetic relationships of the strains as derived from 16S rRNA gene sequence comparisons revealed them as members of the Alphaproteobacteria. The 16S rRNA gene sequences of the isolates were very similar (>99% similarity) and exhibited similarities ranging from 93 to 99% with the most closely related species that were Chelatococcus daeguensis, Chelatococcus sambhunathii,Chelatococcus asaccharovorans, Bosea minatitlanensis, Bosea thiooxidans and Methylobacterium lusitanum. Strains MW9, MW10, MW13 and MW14 grew optimally in MSM with glucose, whereas strains MW11 and MW12 preferred glycerol as sole carbon source for growth and poly(3HB) accumulation. The highest cell density and highest poly(3HB) content attained were 4·8g l(-l) (cell dry weight) and 73% (w/w), respectively. Cells of all strains grew at temperatures between 37 and 55°C with the optimum growth at 50°C.
New PHA-accumulating thermophilic bacterial strains were isolated and characterized to produce poly(3HB) from glucose or glycerol in MSM at 50°C. SSCAs formation was reported during growth.
To the best of our knowledge, this is the first report on the formation of SSCAs by PHA-accumulating bacteria and also by thermophilic bacteria. PHA-producing thermophiles can significantly reduce the costs of fermentative PHA production.
本研究旨在从德国好氧有机废物处理厂和埃及温泉中分离出能够利用廉价碳源在高温下经济可行地生产聚（3-羟基丁酸酯）（PHB）的嗜热细菌。
从德国好氧有机废物处理厂和埃及温泉中富集嗜热细菌。在含有不同碳源的无机盐培养基（MSM）中，使用尼罗红对疏水性细胞内含物进行活菌染色法，分离出 6 株革兰氏阴性菌。在本研究使用的培养条件下，MW9、MW11、MW12、MW13 和 MW14 株在生长过程中形成稳定的星形细胞聚集体（SSCA）；只有 MW10 株由自由生活的杆状细胞组成。基于 16S rRNA 基因序列比较得出的菌株系统发育关系表明它们是α变形菌的成员。分离株的 16S rRNA 基因序列非常相似（>99%相似度），与最密切相关的物种Chelatococcus daeguensis、Chelatococcus sambhunathii、Chelatococcus asaccharovorans、Bosea minatitlanensis、Bosea thiooxidans 和 Methylobacterium lusitanum 的相似度在 93%至 99%之间。MW9、MW10、MW13 和 MW14 株在 MSM 中以葡萄糖为最佳生长碳源，MW11 和 MW12 株则以甘油为唯一碳源用于生长和 PHB 积累。获得的最高细胞密度和 PHB 含量分别为 4.8g l(-1)（细胞干重）和 73%（w/w）。所有菌株的细胞在 37 至 55°C 之间生长，最适生长温度为 50°C。
从葡萄糖或 MSM 中的甘油中分离出了新的聚（3-羟基丁酸酯）积累嗜热细菌菌株，并在 50°C 下进行了表征。在生长过程中报告了星形细胞聚集体的形成。
据我们所知，这是首次报道聚（3-羟基丁酸酯）积累细菌和嗜热细菌形成星形细胞聚集体。产 PHB 的嗜热菌可以显著降低发酵 PHB 生产的成本。
