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Metab Eng. 2017 Nov;44:273-283. doi: 10.1016/j.ymben.2017.10.010. Epub 2017 Oct 28.

Engineering photosynthetic production of L-lysine.

Author information

1
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, United States; Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI 53706, United States.
2
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, United States.
3
Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI 53706, United States; Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI 53706, United States; Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI 53706, United States; Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, United States.
4
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, United States; Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI 53706, United States. Electronic address: pfleger@engr.wisc.edu.

Abstract

L-lysine and other amino acids are commonly produced through fermentation using strains of heterotrophic bacteria such as Corynebacterium glutamicum. Given the large amount of sugar this process consumes, direct photosynthetic production is intriguing alternative. In this study, we report the development of a cyanobacterium, Synechococcus sp. strain PCC 7002, capable of producing L-lysine with CO2 as the sole carbon-source. We found that heterologous expression of a lysine transporter was required to excrete lysine and avoid intracellular accumulation that correlated with poor fitness. Simultaneous expression of a feedback inhibition resistant aspartate kinase and lysine transporter were sufficient for high productivities, but this was also met with a decreased chlorophyll content and reduced growth rates. Increasing the reductant supply by using NH4+, a more reduced nitrogen source relative to NO3-, resulted in a two-fold increase in productivity directing 18% of fixed carbon to lysine. Given this advantage, we demonstrated lysine production from media formulated with a municipal wastewater treatment sidestream as a nutrient source for increased economic and environmental sustainability. Based on our results, we project that Synechococcus sp. strain PCC 7002 could produce lysine at areal productivities approaching that of sugar cane to lysine via fermentation using non-agricultural lands and low-cost feedstocks.

KEYWORDS:

Amino acids; Cyanobacteria; Lysine; Metabolic engineering; Synechococcus sp. PCC 7002

PMID:
29111438
PMCID:
PMC5776718
DOI:
10.1016/j.ymben.2017.10.010
[Indexed for MEDLINE]
Free PMC Article

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