Sequential grafting of PEI on PDA-anchored graphene oxide for enhanced xylose dehydrogenase Catalysis: Positively charged surface interfaces and mechanistic insights via molecular simulation

In this work, graphene oxide (GO) composites, sequentially enhanced with polydopamine (PDA) and polyethyleneimine (PEI), were developed for the innovative immobilization of xylose dehydrogenase (XylB). These composites were designed to achieve positively charged surfaces, aiming to explore the potential interactions between the enzyme and the modified composites. The focus was particularly on determining whether these modifications could improve the enzyme's catalytic performance and stability. Characterization was performed using Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM). Molecular dynamics simulations elucidated the structure-function correlations of immobilized XylB, revealing significant enhancements in thermal stability and catalytic performance compared to its free counterpart. Notably, the immobilized enzyme retained over 85 % of its activity after four consecutive usage cycles and exhibited double the residual activity compared to free XylB after 30 days of storage at 4 °C. Additionally, the immobilized system achieved a 1.4-fold increase in xylonic acid yield relative to the free system. This approach not only highlights the potential of advanced material composites in industrial enzyme applications but also sets a foundation for further research into sustainable biocatalyst technologies.