One of the relevant problems in today's agriculture is related to phytopathogenic microorganisms that cause between 30–40% of crop losses. Synthetic chemical pesticides and antibiotics have brought human and environmental health problems and microbial resistance to these treatments. So, the search for natural alternatives is necessary. The genus Streptomyces have broad biotechnological potential, being a promising candidate for the biocontrol of phytopathogenic microorganisms. The efficacy of some species of this genus in plant protection and their continued presence in the intensely competitive rhizosphere is due to its great potential to produce a wide variety of soluble bioactive secondary metabolites and volatile organic compounds. However, more attention is still needed to develop novel formulations that could increase the shelf life of streptomycetes, ensuring their efficacy as a microbial pesticide. In this sense, encapsulation offers an advantageous and environmentally friendly option. The present review aims to describe some phytopathogenic microorganisms with economic importance that require biological control. In addition, it focuses mainly on the Streptomyces genus as a great producer of secondary metabolites that act on other microorganisms and plants, exercising its role as biological control. The review also covers some strategies and products based on Streptomyces and the problems of its application in the field.

Essential oils are volatile substances of an oily nature present in all plants. They are industrially used as high-value substances for their biological properties in the elaboration of various products in multiple such as pharmaceuticals, food, cosmetics, etc.Today it is known that essential oils have a composite composition and are mainly made up of hydrocarbons and oxygenated compounds, being the trace components contained in these substances, those responsible for providing the odor they possess. Commonly, essential oils are extracted through so-called conventional, where high temperatures and solvents dominate the processes. However, nowadays, multiple emerging techniques have been used to carry out its extraction to achieve better yields, preserve the integrity of the components and reduce the environmental impact that conventional extraction systems imply. This paper addresses a review of conventional systems and emerging technologies that are currently used for the extraction of essential oils.

The study presents the design of a magnetic nanosystem functionalised with Escherichia coli for bacteriophage isolation. The chitosan-coated nanoparticles (C-MNP) were synthesised by coprecipitation, then functionalised with E. coli cells. Different concentrations of C-MNP and incubation times were tested. The immobilisation kinetics and adsorption isotherm were studied. The kinetics was described with the pseudo-stationary state after 30 min. The isotherm was linearized in the Freundlich model. Thermogravimetric analysis verified the functionalisation of C-MNP with E. coli. The complex was used for the extraction of coliphage, for the analysis of the effect of time and salt concentration on phage desorption, and phage extractions with the reuse of the magnetic nanosystem. Compared with traditional methods, an increase in the phage titre collected with the nanocomplex was achieved. The obtained results suggest that C-MNP/E. coli nanosystem can be used at least three cycles for the phage extraction. The release of the phages from the nanosystem was sensitive to the salt concentration. The use of a designed nano-bio complex allowed a rapid and efficient separation of the phages from the water sample under the application of an external magnetic field, and with the possibility of reusing the magnetic complex.

The goals of the present study were to characterize the phages isolated by magnetic nanocomplex, to determine the effect of natural polyphenols on phage activity against E. coli and the stability of free and encapsulated bacteriophages under UV irradiation, and their efficacy against E. coli on romaine lettuce (Lactuca sativa L. var. longifolia) as a fresh food model. The morphology of the two magnetically isolated phages were characterized using the transmission electron microscope (TEM). All isolated phages were classified in a morphological family of tailed phages of the order Caudovirales, Myoviridae family. The PCR results showed that the stx1 and cI genes were not on any phage. Assays were carried out to determine the effect of four polyphenolic natural extracts on phages under UV radiation. The highest activity and stability of phages expressed in phage titer (PFU/ml) were observed in the presence of polyphenols from tarbush leaves (Flourensia cernua DC). Coliphages were encapsulated in alginate/chitosan and alginate/PVA carriers with and without polyphenols from tarbush leaves. Encapsulation led to a higher phage stability under UV radiation. All encapsulated formulations and free coliphages were applied on the surfaces of romaine lettuce containing E. coli cells. An effective reduction of 2 log of E. coli titers from lettuce was observed. Encapsulated phage formulations with and without polyphenols from tarbush leaves could be considered for future application in fresh food preservation.

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