Anaerobic butanol production driven by oxygen-evolving photosynthesis using the heterocyst-forming multicellular cyanobacterium Anabaena sp. PCC 7120
Anaerobic butanol production driven by oxygen-evolving photosynthesis using the heterocyst-forming multicellular cyanobacterium Anabaena sp. PCC 7120
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DOI：
10.1007/s00253-019-09635-z
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发表时间：
2019-03-01
影响因子：
5
通讯作者：
Ehira, Shigeki
中科院分区：
文献类型：
--
作者：
Higo, Akiyoshi;Ehira, Shigeki
蓝细菌是产氧光合细菌。已建立的基因操作方法和最近开发的基因调控工具使得蓝藻，特别是单细胞蓝藻能够通过光合作用将二氧化碳转化为生物燃料和有价值的化学物质。然而，引入蓝细菌的酶的氧敏感性在某些情况下会妨碍生产力。鱼腥藻属PCC 7120 是一种丝状蓝细菌，由数百个营养细胞组成，进行产氧光合作用。缺氮后，异形细胞（一种固氮的特化细胞）以半规则的间隔从营养细胞中分化出来。异形胞内的微氧环境保护氧不稳定的固氮酶免受氧气的影响。这项研究旨在将异形细胞重新用作宿主，在光合作用条件下用氧敏感酶生产化学物质。在此，创建了在异形胞内表达来自厌氧菌丙酮丁醇梭菌的1-丁醇合成途径的酶的鱼腥藻菌株。表达对氧高度敏感的 Bcd/EtfAB 复合物的菌株即使在光合作用条件下也能产生 1-丁醇。此外，产丁醇鱼腥藻菌株的每个异形细胞的 1-丁醇产量比具有相同组 1-丁醇合成途径基因的单细胞蓝细菌的每个细胞高五倍。因此，我们的研究表明鱼腥藻异形体作为由放氧光合作用驱动的厌氧生产底盘的有用性。
Cyanobacteria are oxygen-evolving photosynthetic bacteria. Established genetic manipulation methods and recently developed gene-regulation tools have enabled the photosynthetic conversion of carbon dioxide to biofuels and valuable chemicals in cyanobacteria, especially in unicellular cyanobacteria. However, the oxygen sensitivity of enzyme(s) introduced into cyanobacteria hampers productivity in some cases. Anabaena sp. PCC 7120 is a filamentous cyanobacterium consisting of a few hundred of vegetative cells, which perform oxygenic photosynthesis. Upon nitrogen deprivation, heterocysts, which are specialized cells for nitrogen fixation, are differentiated from vegetative cells at semiregular intervals. The micro-oxic environment within heterocysts protects oxygen-labile nitrogenase from oxygen. This study aimed to repurpose the heterocyst as a host for the production of chemicals with oxygen-sensitive enzymes under photosynthetic conditions. Herein, Anabaena strains expressing enzymes of 1-butanol synthetic pathway from the anaerobe Clostridium acetobutylicum within heterocysts were created. A strain that expressed a highly oxygen-sensitive Bcd/EtfAB complex produced 1-butanol even under photosynthetic conditions. Furthermore, the 1-butanol production per heterocyst cell of a butanol-producing Anabaena strain was fivefold higher than that per cell of unicellular cyanobacterium with the same set of 1-butanol synthetic pathway genes. Thus, our study showed the usefulness of Anabaena heterocysts as a chassis for anaerobic production driven by oxygen-evolving photosynthesis.