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<p>The wide application of poly-<i>β</i>-hydroxybutyrate (PHB) is limited by the increasing costs of organic carbon feedstocks. Cyanobacteria can capture CO<sub>2</sub> to produce PHB, but they face high production costs from the CO<sub>2</sub> supply. NaHCO<sub>3</sub> has been shown to be a superior alternative for delivering CO<sub>2</sub> in algal cultivation. In this study, high-concentration NaHCO<sub>3</sub> was used as both a stress inducer for PHB induction and a superior approach for supplying inorganic carbon to cyanobacteria cells. The results showed that the cyanobacterium <i>Synechocystis</i> sp. PCC6803 achieved the highest PHB content (27.93%) under 0.20 mol L<sup>-1</sup> NaHCO<sub>3</sub>, combined with high light (200 μmol photons m<sup>-2</sup> s<sup>-1</sup>) and nitrogen-phosphorus deficiency. Analysis of the expression levels of key PHB biosynthesis genes revealed that <i>phaC</i> and <i>phaE</i> are significantly upregulated by 7.78- and 11.66-fold, respectively. Further experimental results demonstrated that cells respond to stress by reducing reactive oxygen species (ROS) levels while increasing antioxidant enzyme activities, thereby promoting PHB accumulation. These findings indicate that high-concentration NaHCO<sub>3</sub> serves as both an efficient inorganic carbon source and a stress inducer for PHB accumulation in <i>Synechocystis</i> under stress conditions. This study provides a sustainable approach for PHB production through photosynthesis without organic carbon feed.</p> Graphic Abstract <p></p>

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NaHCO3-driven poly-β-hydroxybutyrate biosynthesis in Synechocystis sp. PCC6803 under multi-stress conditions

  • 期刊论文

  • 发表日期：

    2025年11月10日

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  • Ximing Li,
  • Guozhan Liang,
  • Yaling Liang,
  • Fantao Kong,
  • Zhanyou Chi

摘要

The wide application of poly-β-hydroxybutyrate (PHB) is limited by the increasing costs of organic carbon feedstocks. Cyanobacteria can capture CO2 to produce PHB, but they face high production costs from the CO2 supply. NaHCO3 has been shown to be a superior alternative for delivering CO2 in algal cultivation. In this study, high-concentration NaHCO3 was used as both a stress inducer for PHB induction and a superior approach for supplying inorganic carbon to cyanobacteria cells. The results showed that the cyanobacterium Synechocystis sp. PCC6803 achieved the highest PHB content (27.93%) under 0.20 mol L-1 NaHCO3, combined with high light (200 μmol photons m-2 s-1) and nitrogen-phosphorus deficiency. Analysis of the expression levels of key PHB biosynthesis genes revealed that phaC and phaE are significantly upregulated by 7.78- and 11.66-fold, respectively. Further experimental results demonstrated that cells respond to stress by reducing reactive oxygen species (ROS) levels while increasing antioxidant enzyme activities, thereby promoting PHB accumulation. These findings indicate that high-concentration NaHCO3 serves as both an efficient inorganic carbon source and a stress inducer for PHB accumulation in Synechocystis under stress conditions. This study provides a sustainable approach for PHB production through photosynthesis without organic carbon feed.

Graphic Abstract