Kojibiose as a sustainable bioactive molecule: Experimental and DFT insights into antibacterial activity and electronic properties

In this work, the structural, electronic, vibrational, and biological properties of Kojibiose (KB), a naturally
occurring disaccharide, were assessed using a combination of experimental and computational methods. The molecular geometry was optimized by means of Density Functional Theory (DFT) calculations at the B3LYP/6- 311++G(d,p) level, which yielded comprehensive information on bond lengths, bond angles, dihedral angles, and intramolecular hydrogen bonding interactions that stabilize the pyranose ring structure. Whereas NBO and HOMO-LUMO analyses demonstrated notable intramolecular charge delocalization and electronic stability, vibrational analyses, backed by FT-IR spectra and Potential Energy Distribution (PED), validated distinctive
functional group frequencies. Significant nonlinear optical response was suggested by topological descriptors and
NLO property calculations, including dipole moment, polarizability, and first-order hyperpolarizability, while
UV-Visible spectral analysis revealed prominent electronic transitions, suggesting possible photophysical activity. Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli were both effectively inhibited by
antibacterial activity assessed using the agar well diffusion method, with inhibition zones that were comparable
to those of common antibiotics. The combination of measurable bioactivity, stability, and strong electronic
properties suggests that KB has promising multifunctional qualities appropriate for optoelectronic and pharmaceutical applications.