Sekar Narendran, Jain Rachit, Yan Yajun, Ramasamy Ramaraja P
Nano Electrochemistry Laboratory, College of Engineering, University of Georgia, Athens, Georgia, 30602.
Biosynthetic Engineering and Biocatalysis Laboratory, College of Engineering, University of Georgia, Athens, Georgia.
Biotechnol Bioeng. 2016 Mar;113(3):675-9. doi: 10.1002/bit.25829. Epub 2015 Sep 18.
Photosynthetic energy conversion using natural systems is increasingly being investigated in the recent years. Photosynthetic microorganisms, such as cyanobacteria, exhibit light-dependent electrogenic characteristics in photo-bioelectrochemical cells (PBEC) that generate substantial photocurrents, yet the current densities are lower than their photovoltaic counterparts. Recently, we demonstrated that a cyanobacterium named Nostoc sp. employed in PBEC could generate up to 35 mW m(-2) even in a non-engineered PBEC. With the insights obtained from our previous research, a novel and successful attempt has been made in the current study to genetically engineer the cyanobacteria to further enhance its extracellular electron transfer. The cyanobacterium Synechococcus elongatus PCC 7942 was genetically engineered to express a non-native redox protein called outer membrane cytochrome S (OmcS). OmcS is predominantly responsible for metal reducing abilities of exoelectrogens such as Geobacter sp. The engineered S. elongatus exhibited higher extracellular electron transfer ability resulting in approximately ninefold higher photocurrent generation on the anode of a PBEC than the corresponding wild-type cyanobacterium. This work highlights the scope for enhancing photocurrent generation in cyanobacteria, thereby benefiting faster advancement of the photosynthetic microbial fuel cell technology.
近年来，利用自然系统进行光合能量转换的研究越来越多。光合微生物，如蓝藻，在光生物电化学电池（PBEC）中表现出光依赖的产电特性，可产生大量光电流，但其电流密度低于相应的光伏电池。最近，我们证明了一种名为念珠藻属的蓝藻即使在非工程化的PBEC中也能产生高达35 mW m(-2) 的功率。基于我们之前研究获得的见解，本研究进行了一项新颖且成功的尝试，对蓝藻进行基因工程改造，以进一步增强其细胞外电子转移。对聚球藻属蓝藻PCC 7942进行基因工程改造，使其表达一种名为外膜细胞色素S（OmcS）的非天然氧化还原蛋白。OmcS主要负责诸如地杆菌属等外生电子菌的金属还原能力。经过基因工程改造的聚球藻表现出更高的细胞外电子转移能力，在PBEC的阳极上产生的光电流比相应的野生型蓝藻高出约九倍。这项工作突出了提高蓝藻光电流产生的潜力，从而有利于光合微生物燃料电池技术更快地发展。
