Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, USA.
mBio. 2012 Aug 7;3(4):e00197-12. doi: 10.1128/mBio.00197-12. Print 2012.
The relationship between dinitrogenase-driven H(2) production and oxygenic photosynthesis was investigated in a unicellular cyanobacterium, Cyanothece sp. ATCC 51142, using a novel custom-built photobioreactor equipped with advanced process control. Continuously illuminated nitrogen-deprived cells evolved H(2) at rates up to 400 µmol ⋅ mg Chl(-1) ⋅ h(-1) in parallel with uninterrupted photosynthetic O(2) production. Notably, sustained coproduction of H(2) and O(2) occurred over 100 h in the presence of CO(2), with both gases displaying inverse oscillations which eventually dampened toward stable rates of 125 and 90 µmol ⋅ mg Chl(-1) ⋅ h(-1), respectively. Oscillations were not observed when CO(2) was omitted, and instead H(2) and O(2) evolution rates were positively correlated. The sustainability of the process was further supported by stable chlorophyll content, maintenance of baseline protein and carbohydrate levels, and an enhanced capacity for linear electron transport as measured by chlorophyll fluorescence throughout the experiment. In situ light saturation analyses of H(2) production displayed a strong dose dependence and lack of O(2) inhibition. Inactivation of photosystem II had substantial long-term effects but did not affect short-term H(2) production, indicating that the process is also supported by photosystem I activity and oxidation of endogenous glycogen. However, mass balance calculations suggest that carbohydrate consumption in the light may, at best, account for no more than 50% of the reductant required for the corresponding H(2) production over that period. Collectively, our results demonstrate that uninterrupted H(2) production in unicellular cyanobacteria can be fueled by water photolysis without the detrimental effects of O(2) and have important implications for sustainable production of biofuels.
The study provides an important insight into the photophysiology of light-driven H(2) production by the nitrogen-fixing cyanobacterium Cyanothece sp. strain ATCC 51142. This work is also of significance for biotechnology, supporting the feasibility of "direct biophotolysis." The sustainability of the process, highlighted by prolonged gas evolution with no clear sign of significant decay or apparent photodamage, provides a foundation for the future development of an effective, renewable, and economically efficient bio-H(2) production process.
本研究使用新型定制光生物反应器和先进的过程控制，研究了固氮酶驱动的 H2 生产与产氧光合作用之间的关系，该光生物反应器配备了新型定制光生物反应器和先进的过程控制。在连续光照下，氮饥饿细胞以高达 400µmol ⋅ mg Chl(-1) ⋅ h(-1)的速率进化 H2，同时不间断地产生光合 O2。值得注意的是，在 CO2 存在下，H2 和 O2 的共生产生持续了 100 小时以上，两种气体都呈相反的振荡，最终分别稳定在 125 和 90µmol ⋅ mg Chl(-1) ⋅ h(-1)的速率。当 CO2 被省略时，没有观察到振荡，并且 H2 和 O2 演化速率呈正相关。实验过程中，叶绿素含量稳定，基线蛋白和碳水化合物水平维持，叶绿素荧光测定的线性电子传递能力增强，进一步支持了该过程的可持续性。原位光饱和分析表明，H2 生产具有强烈的剂量依赖性，并且不受 O2 抑制。光系统 II 的失活具有长期的重大影响，但不影响短期 H2 生产，表明该过程还得到光系统 I 活性和内源性糖原氧化的支持。然而，质量平衡计算表明，在光下碳水化合物的消耗最多可能不超过该期间相应 H2 生产所需还原剂的 50%。总的来说，我们的结果表明，在没有 O2 有害影响的情况下，单细胞蓝藻中的不间断 H2 生产可以由水的光解提供燃料，这对生物燃料的可持续生产具有重要意义。
该研究为固氮蓝藻 Cyanothece sp. 菌株 ATCC 51142 的光驱动 H2 生产的光生理学提供了重要的见解。这项工作对生物技术也具有重要意义，支持“直接生物光解”的可行性。该过程的可持续性，通过长时间的气体演化而没有明显的明显衰减或明显的光损伤迹象来突出，为未来开发有效、可再生和经济高效的生物 H2 生产过程奠定了基础。
Zotero 插件
