The use of biopolymers for encapsulating active ingredients is a well-established approach, with ionotropic gelation representing a viable technique. This method allows the use of various cross-linking agents, though the physicochemical properties of the resulting materials can vary depending on the cross-linker selected. This study aimed to evaluate calcium (Ca2+) and aluminum (Al3+) ions as cross-linkers for the formation of carboxymethylcellulose (CMC) microbeads that can carry biological agents. Following comparative analyses, the most effective cross-linker was used for encapsulating the entomopathogenic fungus Beauveria bassiana strain IBCB66. Encapsulation of B. bassiana within a biopolymer bead matrix was found to be a promising strategy to preserve its biological control properties. Beads cross-linked with Al3+ (CMCAl3+) demonstrated superior thermal stability (Tₘax of 165. 76 and 386. 71 °C) and swelling capacity (≈800%) compared to those cross-linked with Ca2+ (Tₘax of 211. 78, 223. 22, 309. 29, and 368. 95 °C, and swelling capacity of ≈200%). CMCAl3+ beads also exhibited a uniform average size (1. 92 ± 0. 11 mm), in contrast to the heterogeneous conglomerates observed in CMCCa2+ beads. Blastospores of B. bassiana were efficiently encapsulated in CMCAl3+ beads via a simple and rapid method, with 85% germination observed on the bead surface after five months of storage at −18 °C. These findings indicate that aluminum is a promising cross-linking agent for CMC-based encapsulation matrices in biological control applications.
Zaldivar et al. (Fri,) studied this question.