New polyelectrolyte complex of chitosan: Preparation, characterization, and application as a biocontrol agent carrier

In this study, a novel water-insoluble polyelectrolyte complex between chitosan and poly(acrylic acid- co-maleic acid) was prepared and characterized. The chitosan used (M̅ v = 23,000–60,000 g/mol) formed water-insoluble polyelectrolyte complexes at pH 2.2–4.8 and water-soluble chitosan oligomers (M̅ v = 2,700 g/mol) at pH 2.2–7.4. The polyelectrolyte complexes formed were used in the preparation of novel carriers for a Trichoderma spp. biocontrol agent. Three types of beads were prepared: noncross-linked chitosan beads, coated with a chitosan/poly(acrylic acid- co-maleic acid) polyelectrolyte complex; genipin-cross-linked chitosan beads; and cross-linked chitosan beads, coated with a chitosan/poly(acrylic acid- co-maleic acid) polyelectrolyte complex. Trichoderma viride was immobilized either in the bulk or in the surface layer of the beads. The microbiological tests confirmed that T. viride immobilized in either mode maintained viability and the capacity to develop and to inhibit the growth of the pathogenic soil microorganisms, Alternaria and Fusarium.