Investigation of <i>Humulus lupulus</i> as a novel adsorbent for protein adsorption: assessment of sorption kinetics, surface topology, and thermal properties using BSA as a model protein

Abstract The increasing production of protein-rich waste, primarily from the household and food industries, associated with the growing global population has imposed a negative environmental burden on society at large. Protein waste is a growing international concern, with more unsegregated waste released from developing countries. This work explored the sorption behavior of amorphous plant extract of Humulus lupulus , towards bovine serum albumin as a representative model protein. The adsorbed proteins analyzed using scanning electron microscopy, revealed irregular beads masking the surface cues and changing the surface smoothness, further validated by atomic force microscopy. The atomic force microscopy analysis showed an increase in the surface potential of pre-adsorbed material (−60.2 mV to 42.5 mV) compared to post-adsorbed complex (−736 mV to 640 mV) suggesting the protein interaction on the plant surface. Differential scanning calorimetry indicated the possible interaction between protein and surface which is responsible for showing a shift in the enthalpy pattern of the surface pre- and post-adsorption. Change in enthalpy pattern, higher surface potential, and shift in Fourier-transform infrared spectroscopy binding pattern indicates an interaction between plant surface and protein that was further validated and confirmed using the adsorption isotherm. The adsorption isotherm towards bovine serum albumin protein followed the Freundlich isotherm with k and n values of 1.143 and 1.157, respectively. The Freundlich isotherm pattern observed for the material has suggested H. lupulus plant extract as a suitable surface for protein adsorption. The study opens the avenue for the adsorption kinetics of different proteins and establishing the plant extract as a suitable remediation solution for environmental sustainability.