Rewiring Carbon Flow in PCC 6803 for a High Rate of CO-to-ethanol Under an Atmospheric Environment

Overview

Journal Front Microbiol

Specialty Microbiology

Date 2023 Jun 16

PMID 37323905

Authors

E-Bin Gao

Junhua Wu

Penglin Ye

Haiyan Qiu

Huayou Chen

Zhen Fang

Affiliations

Soon will be listed here.

Abstract

Cyanobacteria are an excellent microbial photosynthetic platform for sustainable carbon dioxide fixation. One bottleneck to limit its application is that the natural carbon flow pathway almost transfers CO to glycogen/biomass other than designed biofuels such as ethanol. Here, we used engineered sp. PCC 6803 to explore CO-to-ethanol potential under atmospheric environment. First, we investigated the effects of two heterologous genes (pyruvate decarboxylase and alcohol dehydrogenase) on ethanol biosynthesis and optimized their promoter. Furthermore, the main carbon flow of the ethanol pathway was strengthened by blocking glycogen storage and pyruvate-to-phosphoenolpyruvate backflow. To recycle carbon atoms that escaped from the tricarboxylic acid cycle, malate was artificially guided back into pyruvate, which also created NADPH balance and promoted acetaldehyde conversion into ethanol. Impressively, we achieved high-rate ethanol production (248 mg/L/day at early 4 days) by fixing atmospheric CO. Thus, this study exhibits the proof-of-concept that rewiring carbon flow strategies could provide an efficient cyanobacterial platform for sustainable biofuel production from atmospheric CO.

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