Optimization of Bacillus cereus sp H1 amylase immobilization for an eco-friendly approach to textile processing

Immobilization represents one of the strategies to tackle the challenges related to the cost of production, storage stability, and property improvement of biocatalysts. In this study, the Bacillus cereus sp H1 α-amylase was immobilized using physical adsorption onto CaCO₃ powder and entrapment in calcium alginate beads. Using experimental design, optimized yields of 80.77% and 97.42% were recorded for the adsorbed and encapsulated amylase, respectively. The surface-modified CaCO₃ and Ca-alginate were characterized and confirmed by FTIR and SEM. After immobilization, an upgrade in pH and thermal stabilities was observed with the CaCO₃-immobilized amylase compared to the free counterpart and Ca-alginate form. 65% or 52.45% of the activity was conserved after a 1-h incubation at pH 6.5–7.5 or 65°C, respectively. The Ca-alginate-immobilized amylase maintained over 60% of its activity in the presence of 5 mM Cu²⁺ and Mn²⁺, whereas the soluble enzyme’s activity decreased by 70%. Both immobilized biocatalysts maintained a minimum of 60% activity opposed to surfactants and inhibitors. Nevertheless, the Ca-alginate amylase demonstrated higher resistance to the commercial detergents, preserving at least 88% of its activity. Meanwhile, it retained over than 80% of activity after 35 days of storage at 4°C. The highest stability was observed after 2 reuses, with 55.11% residual activity when using CaCO₃ as support. Furthermore, the obtained immobilized amylases were shown to be highly effective in removing starch stains from cotton fabrics, making them potent candidates for developing green and eco-friendly processes, especially for the textile industry.