Metabolic engineering of <i>Escherichia coli</i> based on adaptive evolution and omics technology for highly efficient l-valine production under oxygen-limited conditions.
This study achieved the highest reported yield and productivity for l-valine production in Escherichia coli, setting a new benchmark for industrial biotechnology.
Where it sits
this study against the rest of the sermorelin corpusSummary and findings
The study focuses on engineering Escherichia coli for efficient l-valine production under oxygen-limited conditions. Through adaptive laboratory evolution and omics analysis, an evolved strain demonstrated improved l-valine yield. The final strain achieved a titer of 93.7 g/L in 28 hours in a 5-L bioreactor.
Abstract
In industrial production, the yield of desired targets derived from carbon sources is frequently diminished by the competitive influence of cellular metabolism within microbial cell factories. The bioproduction of l-valine exemplifies a classic process that is confronted with such a dilemma, substantially hindering its economic industrial-scale production. In this study, we aim to engineer a cell factory capable of efficiently synthesizing l-valine with high yield by minimizing the consumption of its precursor pyruvate through the TCA cycle under oxygen-limited conditions. Metabolic engineering-based adaptive laboratory evolution (ALE) under oxygen-limited conditions resulted in the development of an evolved strain ALE2-40 with better cell growth and enhanced l-valine yield. Through comparative omics analysis and validation experiments, it was uncovered that during the ALE process, both pyruvate dehydrogenase activity and NADH availability were significantly improved. Moreover, beneficial targets have the potential to contribute to the NADH and ATP pools, thereby further promoting l-valine synthesis. Based on these results, reverse engineering of the evolved strain ALE2-40 was further conducted. Ultimately, the final strain VAL19 demonstrated remarkable performance, achieving an impressive l-valine titer of 93.7 g/L within 28 h in a 5-L bioreactor under oxygen-limited conditions, with a remarkable yield of 60.4% from glucose-equivalent to 92.9% of the theoretical yield-and a productivity of 3.35 g/L/h. These results set a new benchmark for the fermentative production of l-valine, with the highest yield and productivity reported so far.
Background
The study addresses the challenge of producing l-valine efficiently in industrial settings, where metabolic processes often reduce yield. Previous efforts have been hindered by the competitive consumption of precursors like pyruvate. This research is significant as it aims to optimize microbial production processes, potentially lowering costs and increasing efficiency in industrial biotechnology.
Methods
The study employed metabolic engineering and adaptive laboratory evolution (ALE) under oxygen-limited conditions to develop a strain of Escherichia coli. Comparative omics analysis was used to identify key metabolic changes. The evolved strain ALE2-40 was reverse-engineered to create the final strain VAL19, which was tested in a 5-L bioreactor for l-valine production.
Results
The primary finding was an l-valine titer of 93.7 g/L achieved within 28 hours, with a yield of 60.4% from glucose, equivalent to 92.9% of the theoretical yield. Productivity was reported at 3.35 g/L/h. The study also noted improvements in pyruvate dehydrogenase activity and NADH availability during the ALE process.
Interpretation
This study sets a new benchmark for l-valine production in microbial systems, achieving the highest reported yield and productivity. While the results are statistically significant, their clinical relevance is limited as the study focuses on industrial applications rather than therapeutic outcomes. The findings could inform future biotechnological applications but require further validation in different contexts.
Key findings
- l-valine titer of 93.7 g/L within 28 h
- 60.4% yield from glucose-equivalent
- 92.9% of the theoretical yield
- productivity of 3.35 g/L/h
- improved pyruvate dehydrogenase activity and NADH availability
Limitations
- microbial model, not human
- industrial focus, not clinical
- results specific to oxygen-limited conditions
- single strain engineering