Corynebacterium glutamicum is renowned for its industrial significance in amino acid production, notably l-glutamate and l-lysine. The demand for NADPH in amino acid biosynthesis, particularly l-lysine, underscores the importance of efficient carbon flux redirection towards the pentose phosphate pathway (PPP). This redirection, achieved through phosphoglucoisomerase (Pgi) deletion, enhances NADPH supply but impacts growth due to feedback inhibition on PPP enzymes. In this study, we delve into the repercussions of Pgi deficiency in C. glutamicum strains, focusing on the phosphotransferase system (PTS)-mediated glucose uptake.
The deletion of the pgi gene in C. glutamicum ATCC 13032 resulted in a strain lacking phosphoglucoisomerase activity, exhibiting poor growth with glucose as the primary substrate. Apart from the anticipated PPP inhibition due to NADPH accumulation, a significant reduction in PTS-mediated glucose uptake was observed in the pgi-deficient C. glutamicum strain. Moreover, transcriptional analyses unveiled abolished expression of ptsG, responsible for encoding the glucose-specific EII permease of the PTS in this mutant. Leveraging these findings, we optimized l-lysine production in a model C. glutamicum strain by pgi deletion and plasmid-mediated ptsG overexpression, resulting in enhanced l-lysine yields and productivity compared to the control strain.
The intricate interplay between NADPH regeneration pathways and carbon flux in C. glutamicum underscores the critical role of the PPP in amino acid production. The study’s focus on ptsG repression in pgi-deficient strains sheds light on a novel target for strain enhancement. The observed reduction in glucose uptake efficiency due to ptsG downregulation highlights a previously unexplored aspect of C. glutamicum metabolism, paving the way for further investigations into the molecular mechanisms governing glucose utilization in these strains.
The study further explored the impact of phosphoglucoisomerase deficiency on growth and substrate consumption in C. glutamicum Δpgi strains, revealing a significant growth impairment and glucose consumption slowdown. Ectopic expression of pgi partially restored the growth phenotype, emphasizing the pivotal role of Pgi in glycolysis and its downstream effects on cellular processes. Additionally, heterologous expression of E. coli transhydrogenase UdhA in C. glutamicum Δpgi strains showed limited improvement in growth on glucose, highlighting the multifaceted nature of NADPH regulation in these strains.
Glucose uptake analyses in pgi-deficient strains elucidated a drastic reduction in PTS-mediated uptake, alongside suppressed ptsG transcription. The rescue of glucose uptake and growth phenotype through ptsG overexpression underscored the significance of PTS components in mitigating the effects of pgi deletion. Moreover, the study’s findings on residual glucose uptake being PTS-dependent in C. glutamicum Δpgi strains shed light on the adaptive mechanisms employed by these bacteria to sustain glucose utilization in the absence of Pgi activity.
The optimization of l-lysine production in pgi-negative C. glutamicum strains highlighted the delicate balance between NADPH availability and biosynthetic pathways. While pgi deletion enhanced l-lysine production, the introduction of E. coli transhydrogenase UdhA resulted in a marked decrease in productivity, emphasizing the intricate regulatory networks governing metabolic flux in these strains. Notably, ptsG overexpression in pgi-deficient l-lysine production strains significantly improved productivity and yield, showcasing the synergistic effects of pgi deletion and ptsG upregulation on amino acid biosynthesis.
In conclusion, the study unraveled the complexities of PTS-mediated glucose uptake in C. glutamicum strains lacking phosphoglucoisomerase activity. By elucidating the regulatory mechanisms underlying glucose utilization in pgi-deficient strains, the research provides valuable insights into metabolic engineering strategies for enhancing amino acid production in industrial bioprocesses. Future investigations delving deeper into the molecular interactions governing glucose uptake regulation in C. glutamicum hold promising avenues for optimizing biotechnological applications of this bacterium.
Key Takeaways:
– Phosphoglucoisomerase deficiency in C. glutamicum strains leads to impaired growth and glucose uptake efficiency.
– Repression of ptsG in pgi-deficient strains hampers PTS-mediated glucose uptake, impacting metabolic flux redirection.
– Overexpression of ptsG in pgi-negative strains enhances l-lysine production, highlighting the potential for metabolic engineering in amino acid biosynthesis.
– Understanding the intricate regulatory networks governing glucose utilization in C. glutamicum sheds light on novel targets for strain optimization in industrial bioprocesses.
Tags: yeast, regulatory, chromatography, upstream
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