Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, United Kingdom.
Department of Biochemistry, University of Cambridge , Cambridge CB2 1QW, United Kingdom.
J Am Chem Soc. 2018 Jan 10;140(1):6-9. doi: 10.1021/jacs.7b08563. Epub 2017 Oct 6.
Factors governing the photoelectrochemical output of photosynthetic microorganisms are poorly understood, and energy loss may occur due to inefficient electron transfer (ET) processes. Here, we systematically compare the photoelectrochemistry of photosystem II (PSII) protein-films to cyanobacteria biofilms to derive: (i) the losses in light-to-charge conversion efficiencies, (ii) gains in photocatalytic longevity, and (iii) insights into the ET mechanism at the biofilm interface. This study was enabled by the use of hierarchically structured electrodes, which could be tailored for high/stable loadings of PSII core complexes and Synechocystis sp. PCC 6803 cells. The mediated photocurrent densities generated by the biofilm were 2 orders of magnitude lower than those of the protein-film. This was partly attributed to a lower photocatalyst loading as the rate of mediated electron extraction from PSII in vitro is only double that of PSII in vivo. On the other hand, the biofilm exhibited much greater longevity (>5 days) than the protein-film (<6 h), with turnover numbers surpassing those of the protein-film after 2 days. The mechanism of biofilm electrogenesis is suggested to involve an intracellular redox mediator, which is released during light irradiation.
光合微生物光电化学输出的影响因素尚未被充分理解，电子转移（ET）过程效率低下可能导致能量损失。在这里，我们系统地比较了光合系统 II（PSII）蛋白膜和蓝藻生物膜的光电化学性质，以获得：（i）光电荷转换效率的损失，（ii）光催化寿命的提高，以及（iii）对生物膜界面 ET 机制的深入了解。这项研究得益于分层结构电极的使用，这些电极可以针对 PSII 核心复合物和集胞藻 PCC 6803 细胞的高/稳定负载进行定制。生物膜产生的介导光电流密度比蛋白膜低 2 个数量级。这部分归因于光催化剂负载较低，因为体外从 PSII 中提取介导电子的速率仅是体内 PSII 的两倍。另一方面，生物膜的寿命比蛋白膜长（>5 天）（<6 小时），在 2 天后，其周转率超过了蛋白膜。生物膜发电的机制被认为涉及到一种细胞内氧化还原介体，该介体在光照下释放。
