Preparation and characterization of silica nanoparticles as an efficient carrier for two bio-detergents based enzymes

摘要

Bio-detergents are new bio-friendly formulas that contain biobased ingredients, including enzymes. In the present study, alkaline protease and alpha-amylase were immobilized via physisorption onto silica nanoparticles (SNPs). The derivatized SNPs served as major components of a prepared bio-detergent. Alkaline protease was produced by the recombinant Bacillus subtilis cells that carry the protease genes on a multiple-copy plasmid, while alpha-amylase was commercially purchased. SNPs were prepared by the sol-gel method and well-characterized through the Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), zeta potential, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The adsorption capacity of the SNPs was determined via colorimetry through the adsorption of methylene blue dye (MB), with approximately 97% adsorption achieved under the conditions employed. The Langmuir isotherm well described the adsorption of MB on SNPs. High immobilization yield for the enzymes was obtained, and the storage stability of SNP-alkaline protease and SNP-alpha-amylase was good, reaching 65% and 85% of their initial activities after 6 weeks of storage at 4 degrees C, respectively. The immobilized enzymes could be reused for 7 cycles. Additionally, the immobilized enzymes retained residual activity to a greater extent than free enzymes in simulated basic detergent solutions. SNPs containing adsorbed alkaline protease and alpha-amylase were mixed with a basic detergent solution, and the washing efficiency of some proteinous and starchy stains was examined through Hunter Lab spectrophotometry. The latter experiments demonstrated that the immobilized enzymes performed well during the washing process.