School of Life Sciences, Arizona State University Tempe, AZ, USA.
The Biodesign Institute, Arizona State University Tempe, AZ, USA.
Front Microbiol. 2014 Dec 10;5:680. doi: 10.3389/fmicb.2014.00680. eCollection 2014.
Cyanobacteria are considered good models for biohydrogen production because they are relatively simple organisms with a demonstrable ability to generate H2 under certain physiological conditions. However, most produce only little H2, revert readily to H2 consumption, and suffer from hydrogenase sensitivity to O2. Strains of the cyanobacteria Lyngbya aestuarii and Microcoleus chthonoplastes obtained from marine intertidal cyanobacterial mats were recently found to display much better H2 production potential. Because of their ecological origin in environments that become quickly anoxic in the dark, we hypothesized that this differential ability may have evolved to serve a role in the fermentation of the photosynthate. Here we show that, when forced to ferment internal substrate, these cyanobacteria display desirable characteristics of physiological H2 production. Among them, the strain L. aestuarii BL J had the fastest specific rates and attained the highest H2 concentrations during fermentation of photosynthate, which proceeded via a mixed acid fermentation pathway to yield acetate, ethanol, lactate, H2, CO2, and pyruvate. Contrary to expectations, the H2 yield per mole of glucose was only average compared to that of other cyanobacteria. Thermodynamic analyses point to the use of electron donors more electronegative than NAD(P)H in Lyngbya hydrogenases as the basis for its strong H2 production ability. In any event, the high specific rates and H2 concentrations coupled with the lack of reversibility of the enzyme, at the expense of internal, photosynthetically generated reductants, makes L. aestuarii BL J and/or its enzymes, a potentially feasible platform for large-scale H2 production.
蓝藻被认为是生物制氢的良好模型，因为它们是相对简单的生物体，在某些生理条件下具有产生 H2 的明显能力。然而，大多数蓝藻只产生少量的 H2，很容易恢复到 H2 的消耗，并且易受氢气酶对 O2 的敏感性的影响。最近从海洋潮间带蓝藻垫中获得的蓝藻 Lyngbya aestuarii 和 Microcoleus chthonoplastes 菌株显示出更好的 H2 产生潜力。由于它们在黑暗中迅速缺氧的环境中的生态起源，我们假设这种差异能力可能是为了在光合作用产物的发酵中发挥作用而进化而来的。在这里，我们表明，当这些蓝藻被迫发酵内部底物时，它们表现出生理产氢的理想特征。其中，L. aestuarii BL J 菌株在光合作用产物发酵过程中具有最快的比特定速率，并达到最高的 H2 浓度，该过程通过混合酸发酵途径进行，生成乙酸盐、乙醇、乳酸盐、H2、CO2 和丙酮酸。与预期相反，与其他蓝藻相比，每摩尔葡萄糖的 H2 产率仅为平均水平。热力学分析表明，Lyngbya 氢化酶中使用比 NAD(P)H 更具电负性的电子供体作为其强产氢能力的基础。无论如何，高比特定速率和 H2 浓度加上酶的不可逆性，牺牲了内部光合作用产生的还原剂，使 L. aestuarii BL J 和/或其酶成为大规模 H2 生产的潜在可行平台。
