An engineered cellobiohydrolase I for sustainable degradation of lignocellulosic biomass

This study provides computational-assisted engineering of the cellobiohydrolase I (CBH-I) from Penicillium verruculosum with simultaneous enhanced thermostability and tolerance in ionic liquids, deep eutectic solvent, and concentrated seawater without affecting its wild-type activity. Engineered triple variant CBH-I R1 (A65R-G415R-S181F) showed 2.48-fold higher thermostability in terms of relative activity at 65°C after 1 h of incubation when compared with CBH-I wild type. CBH-I R1 exhibited 1.87-fold, 1.36-fold, and 1.57-fold higher specific activities compared with CBH-I wild type in [Bmim]Cl (50 g/L), [Ch]Cl (50 g/L), and two-fold concentrated seawater, respectively. In the multicellulases mixture, CBH-I R1 showed higher hydrolytic efficiency to hydrolyze aspen wood compared with CBH-I wild type in the buffer, [Bmim]Cl (50 g/L), and two-fold concentrated seawater, respectively. Structural analysis revealed a molecular basis for the higher stability of the CBH-I structure in which A65R and G415R substitutions form salt bridges (D64 … R65, E411 … R415) and S181F forms π-π interaction (Y155 … F181), leading to stabilize surface-exposed flexible α-helixes and loop in the multidomain β-jelly roll fold structure, respectively. In conclusion, the variant CBH-I R1 could enable efficient lignocellulosic biomass degradation as a cost-effective alternative for the sustainable production of biofuels and value-added chemicals.