Improved stability and reusability of endoglucanase from Clostridium thermocellum by a biosilica-based auto-encapsulation method

The functional improvement of endoglucanase (EG), a key cellulose-hydrolyzing biocatalyst, is imperative for the practical use of cellulosic materials such as lignocellulose, stove and straws. Here, we employed a bio-inspired silica-encapsulation method to improve the stability and reusability of EG. We introduced a new silica-forming peptide (SFP) from Ectocarpus siliculosus at the C-terminus of EG to generate a recombinant fusion protein, EG-SFP, with auto-silicifying ability. We obtained an EG-SFP-encapsulated silica matrix (EG-SFP@Silica) via the EG-SFP-mediated auto-silicification process under ambient conditions. The immobilization efficiency was 90%. The introduction of SFP did not significantly affect the functionality of EG, and moreover, EG-SFP@Silica demonstrated higher thermostability by 5 °C than free EG-SFP or EG. In addition, EG-SFP@Silica retained 90% of its initial residual activity with up to 18 uses. These results provide a platform for the development of a practical enzymatic hydrolysis process for cellulosic materials.