Improving l-threonine production in Escherichia coli by elimination of transporters ProP and ProVWX

Abstract

Background Betaine, an osmoprotective compatible solute, has been used to improve l-threonine production in engineered Escherichia colil-threonine producer. Betaine supplementation upregulates the expression of zwf encoding glucose-6-phosphate dehydrogenase, leading to the increase of NADPH, which is beneficial for l-threonine production. In E. coli, betaine can be taken through ProP encoded by proP or ProVWX encoded by proVWX. ProP is a H+-osmolyte symporter, whereas ProVWX is an ABC transporter. ProP and ProVWX mediate osmotic stress protection by transporting zwitterionic osmolytes, including glycine betaine. Betaine can also be synthesized in E. coli by enzymes encoded by betABIT. However, the influence of ProP, ProVWX and betABIT on l-threonine production in E. coli has not been investigated. Results In this study, the influence of ProP, ProVWX and betABIT on l-threonine production in E. coli has been investigated. Addition of betaine slightly improved the growth of the l-threonine producing E. coli strain TWF001 as well as the l-threonine production. Deletion of betABIT retarded the growth of TWF001 and slightly decreased the l-threonine production. However, deletion of proP or/and proVWX significantly increased the l-threonine production. When proP was deleted, the l-threonine production increased 33.3%; when proVWX was deleted, the l-threonine production increased 40.0%. When both proP and proVWX were deleted, the resulting strain TSW003 produced 23.5 g/l l-threonine after 36 h flask cultivation. The genes betABIT, proC, fadR, crr and ptsG were individually deleted from TSW003, and it was found that further absence of either crr (TWS008) or ptsG (TWS009) improved l-threonine production. TSW008 produced 24.9 g/l l-threonine after 36 h flask cultivation with a yield of 0.62 g/g glucose and a productivity of 0.69 g/l/h. TSW009 produced 26 g/l l-threonine after 48 h flask cultivation with a yield of 0.65 g/g glucose and a productivity of 0.54 g/l/h, which is 116% increase compared to the control TWF001. Conclusions In this study, l-threonine-producing E. coli strains TSW008 and TSW009 with high l-threonine productivity were developed by regulating the intracellular osmotic pressure. This strategy could be used to improve the production of other products in microorganisms.

L-threonine promotes healthspan by expediting ferritin-dependent ferroptosis inhibition in C. elegans

“…1k–m ). We therefore believed that threonine concentrations beyond 10 mM are unlikely to be encountered in nature outside of experimental settings like genetically modified E. coli 26 , whereas the suitable dose range of threonine in this investigation (100–400 μM).

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Overexpression of the key genes in the biosynthetic pathways of lipid A and peptidoglycan in Escherichia coli

“…In this study, the genes related to the initial steps in the biosynthesis of lipid A and PG were overexpressed individually or in combination in E. coli MG1655 to investigate how the cell will be affected when the balance between LPS and PG is broken. Furthermore, some recombinant E. coli cells were tested for producing L‐threonine by overexpression of genes thrA , thrB , and thrC related to L‐threonine biosynthesis, and rhtC encoding the transport of L‐threonine 13–17 …”

Toxicity and inhibition mechanism of gallic acid on physiology and fermentation performance of Escherichia coli

“…Escherichia coli is an ideal strain for producing target products by microbial fermentation in the industry (Pontrelli et al 2018). With the rapid rise and development of genetic engineering technology and metabolic engineering breeding strategies, a large number of genetic engineering strains of E. coli have recently been constructed, signi cantly improving the yield and production e ciency of the target product (Fang et al 2021;Guo et al 2020;Liu et al 2016b; Wang et al 2021).…”