Promotion in Refolding and Heat Stress Tolerance of Proteins by Adsorption Immobilization to Biochar

The heat stress tolerance of hen egg white lysozyme (HEWL) was dramatically enhanced by the adsorption of HEWL on adzuki bean charcoal powder (ABCP), which was prepared from adzuki bean waste by pyrolysis without combustion under a nitrogen atmosphere and then comminution with a jet mill. HEWL was firmly adsorbed on ABCP even at high temperatures. The remaining activity of HEWL adsorbed on ABCP exhibited 30% just after the incubation for 30 min at 90oC, increased with incubation time at 25oC, reached a plateau at 30 min, and became around 50%. On the other hand, there is almost no remaining activity of native HEWL just after the incubation for 30 min at 90oC, and it did not change by the incubation at 25oC. The thermal denaturation curve of HEWL adsorbed on ABCP was shifted to high temperatures, compared to that of native one. Moreover, the half-life of BCP-adsorbed HEWL was 28 min at 90oC while that of native one was 4 min.