Enhancement of lysozyme physicochemical stability and biocatalytic activity through direct electrostatic complexation...

Cellulose nanospheres (CNS) were synthesized as carriers for lysozyme (Lys) using a controlled-injection water-in-oil (W/O) emulsion method, employing cellulose nanocrystals (CNC) derived from cotton linter. Acid hydrolysis of cotton linter (CL) produced CNCs with a tenfold reduction in molecular weight (Mη) and degree of polymerization (DP), enhancing solubility and facilitating smaller particle formation. The optimal CNS formulation (3CNS11) exhibited an average particle size of 242 nm, a polydispersity index (PDI) of 0.4, and a zeta potential (ZP) of -35.27 mV. Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and ZP confirmed successful interaction between CNS and lysozyme, forming stable CNS/Lys complexes. Comparative studies under various temperatures, pH levels and urea concentrations revealed that CNS/Lys retained higher enzymatic activity, with a 35 % increase at 70 °C and a 60 % increase at pH 3. Moreover, CNS/Lys preserved over 80 % of their initial activity across all tested urea concentrations. Antibacterial assays against Bacillus subtilis (B. subtilis) showed a 25 % larger zone of inhibition (ZOI) for CNS/Lys than free lysozyme. These findings highlight the role of CNS in enhancing lysozyme stability and bioactivity, validating its potential as an efficient enzyme carrier.