| Summary: | Production of xylitol via biotechnological process is a potential substitute for the conventional production of xylitol via chemical route due to it being inexpensive and eco-friendly. Biotechnological approaches, particularly using genetically modified Escherichia coli (E. coli), offer a promising alternative to conventional chemical methods. Despite efforts to enhance xylitol yield, achieving high production levels remains a challenge. This research compared the metabolic profiles of free and immobilised recombinant E. coli, identified affected metabolic pathways due to heterologous gene expression, and explored the correlations between xylitol and other metabolites. Free and immobilised recombinant E. coli with deleted phosphoglucose isomerase (pgi) gene and cloned with xylitol phosphate dehydrogenase (xpdh) gene were cultivated at 37 oC, 180 rpm for 24 h. The maximum specific growth rates of free and immobilised E. coli were 0.0459 h-1 and 0.0362 h-1 respectively, indicating a slower growth of the immobilised cells. However, despite the slower growth rate, the immobilised cells produced significantly more xylitol than the free cells with 26.17% improvement at 24 h. Apart from that, GC-MS was employed to identify the metabolites present in free and immobilised recombinant E. coli and a total of 87 and 77 unique metabolites were detected in free and immobilised cells respectively. Furthermore, the results from this study also revealed significant differences between the metabolic profiles of free and immobilised cells with specific pathways being uniquely affected in immobilised cells, namely monobactam biosynthesis, and selenocompound metabolism pathways. Moreover, the study highlights notable shift in amino acids metabolisms, suggesting their critical roles in the bioproduction of xylitol. The immobilised cells demonstrated not only a capacity for a higher xylitol production, but also metabolic alterations that underscore the complexity of cellular responses to immobilisation and genetic modifications. Other than that, correlation analysis revealed metabolites that have high correlation coefficient (≥ 0.7) with xylitol during production, suggesting potential associations with xylitol synthesis, which could be investigated further to facilitate a deeper understanding of their metabolic dynamics. In conclusion, the results gained from this study contributed to a deeper understanding of metabolic foundation of xylitol production in recombinant E. coli emphasising the potential of immobilisation to improve xylitol bioproduction processes. This study lays the groundwork for further optimisation of xylitol production, promoting for targeted metabolic engineering and the refinement of immobilisation techniques to harness the full productive capacity of recombinant E. coli, particularly the one that utilises glucose as substrate.
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