Utilization of waste glycerol for the production of biocontrol agents nigericin and niphimycin by Streptomyces hygroscopicus: bioprocess development

Antimicrobial and insecticidal activity of spray dried juniper berry (Juniperus communis L.) essential oil microcapsules prepared by using gum arabic and maltodextrin

This study was carried out to optimize spray drying conditions for juniper berry essential oil (JBEO) microencapsulation. The coating material for encapsulation was a combination of maltodextrin (MD) and gum arabic (GA). The wall material content, inlet air temperature and feed flow rate were optimized to obtain small particle size and high level of powder production, with high JBEO loading and encapsulation efficiency, small powder moisture and hygroscopicity. The optimal formulation was characterized by FTIR spectroscopy and used for investigation of antimicrobial and insecticidal activities. The obtained optimal conditions for JBEO microencapsulation were inlet air temperature of 140 °C, feed flow rate of 2.43 cm3 min-1 and wall/core ratio of 3:1. The considerably greater JBEO oil retention was obtained by using spray dried GA compared to GA in a form of the branched polysaccharide. Microencapsulated JBEO showed antibacterial and antifungal activities at oil concentrations 1-5 %. Strong repellency against S. oryzae and A. obtectus were achieved at concentration of JBEO of 2 %, while for mortality of 65.5 % (S. oryzae) and 85.5 % (A. obtectus) after 72 h, the 5 % of JBEO were required. JBEO microencapsulation could be a promising method for the production of biopesticides to reduce the use of chemical preparations.

Streptomyces Strains and Their Metabolites for Biocontrol of Phytopathogens in Agriculture

Sustainable agriculture is increasingly linked to biological pesticides as alternatives to agro-chemicals. Streptomyces species suppress plant diseases through their unique traits and numerous metabolites. Although many Streptomyces strains have been developed into commercial products, their roles in the biocontrol of phytopathogens and mechanisms of functional metabolite synthesis remain poorly understood. In this review, biocontrol of plant diseases by Streptomyces is summarized on the basis of classification of fungal and bacterial diseases and secondary metabolites produced by Streptomyces that act on phytopathogenic microorganisms are discussed. The associated non-ribosomal peptide synthetases and polyketide synthetases responsible for biosynthesis of these secondary metabolites are also investigated, and advances in fermentation of Streptomyces are described. Finally, the need to develop precise and effective biocontrol methods for plant diseases is highlighted.

Nigericin and Geldanamycin Are Phytotoxic Specialized Metabolites Produced by the Plant Pathogen Streptomyces sp. 11-1-2

Plant pathogens use a variety of mechanisms, including the production of phytotoxic specialized metabolites, to establish an infection of host tissue. Although thaxtomin A is considered the key phytotoxin involved in the development of potato scab disease, there is increasing evidence that other phytotoxins can play a role in disease development in some instances.