Ecofriendly\nand Conductive Corn-Cob-Based Biomass\nDriven from Aqueous Deep Eutectic Solvents: A Suitable Media for Enzyme\nStructure, Storage, and Activity at High Temperature

Production of biomaterials from lignocellulosic biomass\nwaste is\nof prime importance for diverse applications. However, the use of\nharsh chemicals, extreme conditions, and tedious processes to convert\nit into useful materials are the major bottlenecks for its application.\nHerein, leftover waste of corn-cob biomass (CB) was converted into\nfunctional carbonaceous material via a solvothermal process using\nwater in deep eutectic solvents (DESs) by employing two DESs namely,\ncholine chloride-glycerol (ChCl-Gly) and ChCl-ethylene glycol (ChCl-EG).\nThe synthesized CB-based solvothermal carbon materials, using CB-ChCl-Gly\nand CB-ChCl-EG, were characterized to verify incorporated morphological\nvariations. The obtained results showed that the synthesized carbon\nmaterials were rich in oxygen functionality with a more porous, globular\nsurface structure. Further, the detailed analysis of the feasibility\nof the synthesized biomaterials as biocompatible carriers for cytochrome-c\n(Cyt-c) was evaluated. The peroxidase-like activity was remarkably\nenhanced up to 1.5-fold compared to the native enzyme. Further, the\nbiocompatibility of these synthesized carbon materials was validated\nusing the Michaelis–Menten equation. Besides this, time- and\ntemperature-dependent studies of Cyt-c after immobilization of these\nbiomass-based carbon materials demonstrated preservation of structural\nintegrity as well as improved enzymatic activity. Various biophysical\ntechniques validated the improved secondary and tertiary structures\nof the enzymes after immobilization. The micrograph obtained using\ntransmission electron microscopy (TEM) microscopy and hydrodynamic\nsize (d<sub>H</sub>) and zeta potential values measured using dynamic\nlight scattering (DLS) showed successful protein immobilization on\nthe synthesized carbon materials. Interestingly, the secondary structure\nof Cyt-c is maintained at higher temperatures in the presence of both\nCB-ChCl-EG and CB-ChCl-Gly carbon materials. Overall, this study elucidates\na sustainable source and ecofriendly method of preparation of solvothermal\ncarbon material and displays its beneficial influence on the activity\nand stability of Cyt-c. Remarkably, proving to be a protein-friendly\nhost, CB will be helpful for long-term protein packing, which may\nprovide a foundation for imaging modalities for the biomolecules with\ndiverse industrial applications.