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Systematic Engineering of Synechococcus elongatus UTEX 2973 for Photosynthetic Production of l-Lysine, Cadaverine, and Glutarate

Zachary A Dookeran, D. R. Nielsen

ACS Synthetic Biology, 2021

21 citations

Abstract

Amino acids and related targets are typically produced by well-characterized heterotrophs including Corynebacterium glutamicum and Escherichia coli. Cyanobacteria offer an opportunity to supplant these sugar-intensive processes by instead directly utilizing atmospheric CO2 and sunlight. Synechococcus elongatus UTEX 2973 (hereafter UTEX 2973) is a particularly promising photoautotrophic platform due to its fast growth rate. Here, we first engineered UTEX 2973 to overproduce l-lysine (hereafter lysine), after which both cadaverine and glutarate production were achieved through further pathway engineering. To facilitate metabolic engineering, the relative activities of a subset of previously uncharacterized promoters were investigated, in each case, while also comparing the effects of both chromosomal (from neutral site NS3) and episomal (from pAM4788) expressions. Using these parts, lysine overproduction in UTEX 2973 was engineered by introducing a feedback-resistant copy of aspartate kinase (encoded by lysCfbr) and a lysine exporter (encoded by ybjE), both from E. coli. While chromosomal expression resulted in lysine production up to just 325.3 ± 14.8 mg/L after 120 h, this was then increased to 556.3 ± 62.3 mg/L via plasmid-based expression, also surpassing prior reports of photoautotrophic lysine bioproduction. Lastly, additional products of interest were then targeted by modularly extending the lysine pathway to glutarate and cadaverine, two 5-carbon, bioplastic monomers.…

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