AUTHOR=Velmurugan Rajendran , Incharoensakdi Aran 

TITLE=Heterologous Expression of Ethanol Synthesis Pathway in Glycogen Deficient Synechococcus elongatus PCC 7942 Resulted in Enhanced Production of Ethanol and Exopolysaccharides

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00074

DOI=10.3389/fpls.2020.00074

ISSN=1664-462X

ABSTRACT=<p>In this study, the <italic>Synechococcus elongatus</italic> PCC 7942 (hereafter <italic>S. elongatus</italic>) was engineered by the <italic>glgC</italic> knockout as well as the insertion of the <italic>pdc</italic>-<italic>adh</italic> genes from two different microorganisms. The insertion of <italic>pdc</italic>-<italic>adh</italic> genes increased the ethanol synthesis with further improvement in the productivity upon the destruction of glycogen synthesis pathway and the supplementation of cofactor. The abolition of glycogen synthesis pathway led to a considerable increase of the engineered <italic>S. elongatus</italic> metabolites involved in the ethanol synthesis pathway. Moreover, the studies on cofactor addition highlighted the importance of Mg<sup>+2</sup>, Zn<sup>+2</sup>, thiamine pyrophosphate, and NADP<sup>+</sup> in ethanol synthesis. The yields of 3856 mg/L ethanol and 109.5 µg/10<sup>8</sup> cells exopolysaccharides were obtained in the engineered <italic>S. elongatus</italic> using a photo-bioreactor under optimized conditions. This enhanced production in ethanol and exopolysaccharides are attributed to the flux of carbon from glycogen synthesis pathway and proper availability of essential components.</p>