PHB (poly-hydroxy-butyrate) represents a promising bioplastic variety with good biodegradation properties. Furthermore, PHB can be produced completely carbon-neutral when synthesized in the natural producer cyanobacterium Synechocystis sp. PCC 6803. This model strain has a long history of various attempts to further boost its low amounts of produced intracellular PHB of ~15 % per cell-dry-weight (CDW). We have created a new strain that lacks the regulatory protein PirC (gene product of sll0944), which causes a rapid conversion of the intracellular glycogen pools to PHB under nutrient limiting conditions. To further improve the intracellular PHB content, two genes from the PHB metabolism, phaA and phaB from the known production strain Cupriavidus necator, were introduced under the regime of the strong promotor PpsbA2. The created strain, termed PPT1 (Δsll0944-REphaAB), produced high amounts of PHB under continuous light as well under day-night rhythm. When grown in nitrogen and phosphor depleted medium, the cells produced up to 63 % / CDW. Upon the addition of acetate, the content was further increased to 81 % / CDW. The produced polymer consists of pure PHB, which is highly isotactic. The achieved amounts were the highest ever reported in any known cyanobacterium and demonstrate the potential of cyanobacteria for a sustainable, industrial production of PHB.

中文翻译：

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最大化集藻囊藻中的PHB含量。PCC 6803：开发一种新的光合作用过量生产菌株

PHB（聚羟基丁酸酯）代表了一种具有良好生物降解特性的有前途的生物塑料品种。此外，当在天然生产者蓝藻Synechocystis sp。中合成时，PHB可以完全碳中和。PCC6803。该模型菌株已有悠久的历史，曾尝试过各种尝试以进一步提高其低产生量的细胞内PHB，每细胞干重（CDW）约为15％。我们创建了一种新的菌株，该菌株缺乏调节蛋白PirC（sll0944的基因产物），该蛋白在营养限制条件下会导致细胞内糖原池快速转化为PHB。为了进一步提高细胞内PHB含量，在强启动子PpsbA2的作用下，引入了来自PHB代谢的两个基因，即来自已知生产菌株Cupriavidus necator的phaA和phaB。产生的应变 称为PPT1（Δsll0944-REphaAB）的PPH1，在连续光照下以及在昼夜节律下均产生大量PHB。在贫氮和缺磷的培养基中生长时，细胞产生的CDW高达63％。加入乙酸盐后，含量进一步增加至81％/ CDW。生成的聚合物由高度等规的纯PHB组成。达到的数量是任何已知的蓝细菌中所报道的最高数量，并且证明了蓝细菌对于PHB的可持续工业生产的潜力。这是高度全同立构的。达到的量是有史以来已知的任何蓝细菌中最高的，证明了蓝细菌对PHB的可持续工业生产的潜力。这是高度全同立构的。达到的量是有史以来已知的任何蓝细菌中最高的，证明了蓝细菌对PHB的可持续工业生产的潜力。