# Sustainable Encapsulation of Biocontrol Agents: Cross-Linker Influence on Carboxymethylcellulose-Based Microbeads

## TL;DR

This paper explores using aluminum ions to create biopolymer beads that effectively preserve and deliver biocontrol fungi for sustainable pest management.

## Contribution

The study identifies aluminum as a superior cross-linker for carboxymethylcellulose beads in encapsulating biocontrol agents.

## Key findings

- CMC beads cross-linked with Al3+ showed higher thermal stability and swelling capacity than those with Ca2+.
- B. bassiana blastospores encapsulated in CMC_Al3+ beads retained 85% germination after five months of storage.
- Al3+-cross-linked beads had a uniform size, unlike the heterogeneous Ca2+-cross-linked beads.

## Abstract

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+ (CMC_Al3+) demonstrated superior thermal
stability (T_max of 165.76 and 386.71 °C) and
swelling capacity (≈800%) compared to those cross-linked with
Ca2+ (T_max of 211.78, 223.22, 309.29,
and 368.95 °C, and swelling capacity of ≈200%). CMC_Al3+ beads also exhibited a uniform average size (1.92 ±
0.11 mm), in contrast to the heterogeneous conglomerates observed
in CMC_Ca2+ beads. Blastospores of B. bassiana were efficiently encapsulated in CMC_Al3+ 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.