Abstract
Glutarate is an important C5 platform chemical produced during the catabolism of L-lysine through 5-aminovalerate (5-AMV) pathway. Here, we first established a whole-cell biocatalysis system for the glutarate production from L-lysine with the engineered Escherichia coli (E. coli) that co-expressed DavAB and GabDT. However, the accumulation of intermediate 5-AMV was identified as one important factor limiting glutarate production. Meanwhile, the negative interaction of co-expressing DavAB and GabDT in a single cell was also confirmed. Here, we solved these problems through engineering a microbial consortium composed of two engineered E. coli strains, BL21-22AB and BL21-YDT, as the whole-cell biocatalysts, each of which contains a part of the glutarate pathway. After the optimization of bioconversion conditions, including temperature, metal ion additives, pH, and cell ratio, 17.2 g/L glutarate was obtained from 20 g/L L-lysine with a yield of 95.1%, which was improved by 19.2% compared with that in a single cell. Little accumulation of 5-AMV was detected. Even at the high substrate concentration, the reduced 5-AMV accumulation and increased glutarate production were achieved. This synthetic consortium produced 43.8 g/L glutarate via a fed-batch strategy, the highest titer reported to date.
Highlights
As the seriousness of environmental problems related to global warming and depletion of oil reserves, the development of sustainable bio-process for petroleum-derived chemicals has attracted increased attention in recent years (Tsuge et al, 2016)
To analyze the aqueous concentrations of L-lysine and 5-AMV, a highperformance liquid chromatography (HPLC) (Agilent 1100 series, Santa Clara, CA, United States) system was used, which was equipped with an evaporative light scattering detector (ELSD) and a Prevail C18 column (250∗4.6 mm, 5 μm, Bio-Rad, Hercules, CA, United States) at 28.5◦C. 0.7% (v/v) trifluoroacetic acid aqueous solution was used as the mobile phase at a flow rate of 1.0 mL/min
We found that the highest glutarate molar yield was only 75.9% under the condition of 20 g/L L-lysine
Summary
As the seriousness of environmental problems related to global warming and depletion of oil reserves, the development of sustainable bio-process for petroleum-derived chemicals has attracted increased attention in recent years (Tsuge et al, 2016). Dicarboxylic acids, especially aliphatic dicarboxylic acids, such as succinate, glutarate, adipate, pimelate, and suberate, are important building blocks for the synthesis of polymers and polyamides, such as polyurethanes, polyester polyols and polyamides (Okino et al, 2008; Gobin et al, 2015). For the chemical synthesis of glutarate, a mixture of cyclohexanone, and Engineering a Microbial Consortium cyclohexanol (KA oils) was oxidized with nitric acid (Paris et al, 2003; Vafaeezadeh and Hashemi, 2016). The cost and environmental concern of chemical methods limited the sustainable production of glutarate in industry. The efficient bio-based process for glutarate production is highly desired
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