engleski

Simultaneously encapsulated chemical and biological agents for plant protection and nutrition

The use of agrochemicals in agriculture had substantial repercussions for the environment, food security as well as human health because some of them are persistent organic pollutants. To diminish the overall exposure to agrochemicals that may end up in the environment, the worldwide intention is the restriction of their use and application of environmentally friendly systems like biofertilizers and/or biopesticides (pesticides derived from natural materials). Biofertilizer formulations usually contain a living microorganism (bacteria, fungi) and a suitable carrier together with additives. Efficient formulation demands a carrier material which must preserve or maintain living organisms in a viable condition during storage and transport as well as must keep its functional properties after application. Encapsulation in microparticles (microspheres/microcapsules) is an advanced technology which is superior to other formulations in terms of living organism protection from the environment, improvement of their viability and possibility of controlled release into the field. Trends of encapsulation in agriculture are focused on the preparation of microparticle formulations involving biological and chemical agents. The main problems that should be solved here are: (i) to choose microparticle that can incorporate biological and chemically active agents and (ii) the presence of active agents in the same compartment should not diminish their activities. Due to benefits of crop protection and nutrition as well as high compatibility, Trichoderma viride spores (biofertilizers) and copper or calcium cations (micro- or macronutrient) were taken as a suitable couple of the chemical and biological agent. We have developed and characterized alginate microspheres and microcapsules (with chitosan layer) prepared by the ionic gelation using copper or calcium cations as a crosslinking agent and loaded with T. viride spores. Simultaneous loading in microparticles revealed that presence in the same compartment does not inhibit bioactivity either of T. viride spores nor gelling cations. Controlled release, that is the successful delivery of bioactive agents to the plants and at the right time is necessary characteristic for all bioactive agents’ delivery systems. To obtain the well-designed delivery system efficient for simultaneous loading and release of bioactive agents to plants at the rate that closely approximates plants demand, it is important to optimize parameters during microparticles preparation. The concentration of gelling cation, microparticle size, and presence of chitosan layer were considered as variables with possible influence on the essential microparticle parameters. The gelation at a fixed amount of sodium alginate and at different concentrations of gelling cation in solution resulted in distinct kinetics and release mechanisms. The increase in the concentration of gelling cation promoted, but the presence of the chitosan layer on microcapsule surface and increase in their size reduced the rate of an bioactive agent release. Fitting to simple Korsmeyer–Peppas empirical model revealed the underlying release mechanism depends on the concentration of gelling cation and presence of T. viride spores as well as on the chitosan layer. The investigation pointed out that proper selection of formulation variables helps in designing microparticles with the controlled release of biofertilizer and micro- and macronutrients for plant protection and nutrition.

microcapsules, microparticles, nutrirtion, protection, time release

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