JIA-2019-11

Journal of Integrative Agriculture 2019, 18(11): 2534–2548 RESEARCH ARTICLE Available online at www.sciencedirect.com ScienceDirect Physicochemical properties and release characteristics of calcium alginate microspheres loaded with Trichoderma viride spores Slaven Jurić 1 , Edyta Đermić 2 , Snježana Topolovec-Pintarić 2 , Marta Bedek 1 , Marko Vinceković 1 1 Department of Chemistry, University of Zagreb Faculty of Agriculture, Zagreb 10000, Croatia 2 Department of Plant Pathology, University of Zagreb Faculty of Agriculture, Zagreb 10000, Croatia Abstract Novel agroformulations for simultaneous delivery of chemical and biologically active agents to the plants were prepared by encapsulation of Trichoderma viride spores in calcium alginate microspheres. The impact of calcium ions concentration on the viability and sporulation of T. viride spores as well as on the microsphere important physicochemical properties were investigated. Intermolecular interactions in microspheres are complex including mainly hydrogen bonds and electrostatic interactions. T. viride germination inside matrix and germ tubes penetration out of microspheres revealed calcium alginate microspheres provide a supportive environment for T. viride growth. Differences in physicochemical properties and bioactive agents release behaviour from microspheres were ascribed to the changes in microsphere structure. Fitting to Korsmeyer- Peppas empirical model revealed the underlying T. viride release mechanism as anomalous transport kinetics (a combination of two diffusion mechanisms and the Type II transport (polymer swelling and relaxation of the polymeric matrix)). The increasing amount of T. viride spores in the surrounding medium is closely related to the release from microspheres and germination. The rate controlling mechanism of calcium release is Fickian diffusion . A decrease in the release rate with increasing calcium ion concentrations is in accordance with the calcium ions effect on the strength of the alginate network structure. T. viride germination inside microsphere diminished the amount of released calcium ions and slowed release kinetics in comparison with microspheres prepared without T. viride. The results indicated investigated agroformulations have a great potential to be used for plant protection and nutrition. Keywords: agroformulations, alginate microspheres, calcium ions, Trichoderma viride , sustainability in storage, are susceptible to attacks by many pathogens that cause severe damage to the plant. A wide range of organisms, mainly bacteria, nematodes, and fungi have been used as biocontrol agents among whom Trichoderma species is the most commonly studied. Their agricultural importance is good antagonistic abilities against soil-born plant pathogenic fungi thanks to different mechanisms of antagonism; the production of antifungal metabolites (antibiosis), competition for space and nutrients, induction of defense responses in plant and mycoparasitism. Investigations also revealed their ability to promote plant growth that was first treated as a side effect of suppression of Received 25 September, 2018 Accepted 8 January, 2019 Correspondence Marko Vinceković, E-mail: mvincekovic@agr.hr © 2019 CAAS. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/) . doi: 10.1016/S2095-3119(19)62634-1 1. Introduction Plants at all stages of their growth, as well harvest products