This study focuses on developing an encapsulated and dehydrated formulation of vegetative actinobacteria cells for an efficient application in sustainable agriculture, both as a fungicidal agent in crop protection and as a growth-stimulating agent in plants. Three strains of actinobacteria were used: one from a collection (Streptomyces sp.) and two natives to agricultural soil, which were identified as S3 and S6. Vegetative cells propagated in a specific liquid medium for mycelium production were encapsulated in various alginate-chitosan composites produced by extrusion. Optimal conditions for cell encapsulation were determined, and cell damage from air-drying at room temperature was evaluated. The fresh and dehydrated composites were characterized by porosity, functional groups, size and shape, and their ability to protect the immobilized vegetative cells' viability. Actinomycetes were immobilized in capsules of 2.1-2.7 mm diameter with a sphericity index ranging from 0.058 to 0.112. Encapsulation efficiency ranged from 50% to 88%, and cell viability after drying varied between 44% and 96%, depending on the composite type, strain, and airflow. Among the three immobilized and dried strains, S3 and S6 showed greater resistance to encapsulation and drying with a 4 Lmin-1 airflow when immobilized in coated and core-shell composites. Encapsulation in alginate-chitosan matrices effectively protects vegetative actinobacteria cells during dehydration, maintaining their viability and functionality for agricultural applications.
Since the late nineteenth century, the agricultural sector has experienced a tremendous increase in chemical use in response to the growing population. Consequently, the intensive and indiscriminate use of these substances caused serious damage on several levels, including threatening human health, disrupting soil microbiota, affecting wildlife ecosystems, and causing groundwater pollution. As a solution, the application of microbial-based products presents an interesting and ecological restoration tool. The use of Plant Growth-Promoting Microbes (PGPM) affected positive production, by increasing its efficiency, reducing production costs, environmental pollution, and chemical use. Among these microbial communities, lactic acid bacteria (LAB) are considered an interesting candidate to be formulated and applied as effective microbes. Indeed, these bacteria are approved by the European Food Safety Authority (EFSA) and Food and Drug Administration (FDA) as Qualified Presumption of Safety statute and Generally Recognized as Safe for various applications. To do so, this review comes as a road map for future research, which addresses the different steps included in LAB formulation as biocontrol, bioremediation, or plant growth promoting agents from the isolation process to their field application passing by the different identification methods and their various uses. The plant application methods as well as challenges limiting their use in agriculture are also discussed.Graphical AbstractThe different processes involved in LAB use as biofertilizers or biocontrol agents.
The study was conducted within the Longstanding Stationary Fertilizer Experiment (LSFE) in IASS Obraztsov Chiflik, Rousse with the aim of establishing the influence of different options of mineral fertilization on yield and resistance to environmental stress and the development of phytopathogens in common wheat.It was found that the highest yield for the period - 6,080 kg ha(-1), was obtained in the experimental plot with full mineral fertilization (N-15 & Rcy;(12)& Kcy;(7)), which represents more than a two-fold increase compared to the average yield obtained from the control. Phytopathological analysis shows that the seeds obtained from the variant with full mineral fertilization have the lowest percentage of phytopathogens (0.75-2.00%) while 22% of the seeds in the control was damaged by Tilletia. The variants with potassium fertilization (K-7) stand out as the most resistant to atmospheric drought during the four-year research period, with the reported values - 58.61 mu S cm(-1), being 12% lower, compared to the control. The highest resistance to soil drought was established for the variants with potassium (K-7) and phosphorus (P-12) fertilization, respectively 83.02 mu S cm(-1) and 83.05 mu S cm(-1).