Recent Advances in Encapsulation Techniques of Plant Growth-Promoting Microorganisms and Their Prospects in the Sustainable Agriculture

Abstract

In addition to changing global demography and global warming, agricultural production systems around the world are threatened by intensive agricultural practices (overuse of land and excessive use of chemical fertilizers and pesticides) that deplete soils by affecting their dynamics and their fertility, pollute the environment, lower production, and alter biodiversity on a large scale. The use of bioformulations based on PGPMs (plant growth-promoting microorganisms) seems to be a promising and sustainable strategy to overcome these threats, thanks to their tolerance to various biotic and abiotic stresses and via their beneficial effects in promising plant growth, pest protection, bioremediation, and restoration of degraded lands. In recent years, particular attention has been paid to encapsulated formulations because they offer several advantages over conventional bioformulation (liquid and solid) related to shelf life, problems of survival and viability in the environment, and the efficiency of rhizospheric colonization. This review focuses on the types of encapsulations and the different technologies used in this process as well as the most commonly used substrates and additives. It also provides an overview on the application of encapsulated bioformulations as biofertilizers, biopesticides, or other biostimulators and summarizes the knowledge of the scientific literature on the development of nanoencapsulation in this sector.

Polymeric Encapsulate of Streptomyces Mycelium Resistant to Dehydration with Air Flow at Room Temperature

“…The Streptomyces mycelium was encapsulated in calcium alginate with YGM medium as a protective agent. The YGM medium is a low-cost protective agent compared to other additives such as trehalose [ 34 ]. The drawback of culture media is their formulation, which may contain anti-gelling substances such as Mg +2 [ 38 , 59 ].…”

“…According to the encapsulation efficiencies reported by these authors and those obtained in the present work, the gum arabic can form a protective material in encapsulation processes, regardless of the process applied. In an encapsulation formulation, the sugars have the function of protecting the vegetative cells against osmotic pressure and desiccation during the capsule-drying step [ 17 , 34 , 77 ]. This type of protection occurs because of the potential of sugars to be absorbed and aggregate in the cytoplasm [ 14 ].…”

“…Trehalose, kaolin, and gum arabic are materials that have been used in combination with other polymers to protect biological agents from dehydration treatments [ 24 , 34 , 37 , 44 , 45 , 46 ]. In the present study, these were used separately in different stages of the immobilization process of the Streptomyces CDBB1232 mycelium ( Supplementary Figure S1 ).…”

“…The inconvenience of moisture removal with heat is the viability loss of the microbial cells because of their high sensitivity to heat or shear stresses, which usually damage the cellular membrane. Thus, the encapsulation of the biological material prior to dehydration is the strategy of interest and under study, considering the great variety of solid supports available (inorganic, organic, and polymeric) and the possibility of modifying their physicochemical properties by integrating into them the appropriate additive or additives ( Supplementary Table S2 ) [ 4 , 14 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ].…”

“…Of the known polymeric supports, alginate is one of the most commonly used in the encapsulation of microbial strains [ 34 , 35 , 36 , 37 ]. Alginate is a biocompatible, biodegradable, and nontoxic support that can be applied to encapsulate hydrophilic active substances.…”