This work aims at characterising polysaccharide-based films without (GA) and with the incorporation of free natamycin (GA-NA) and natamycin-loaded in a smart delivery device consisting in poly(N-isopropylacrylamide) nanohydrogels (GA-PNIPA). Transport properties (water vapour, oxygen and carbon dioxide permeabilities), mechanical properties (tensile strength and elongation-at-break), opacity, water sensitivity (moisture content and contact angle) and thermal properties (differential scanning calorimetry and thermogravimetric analyses) were evaluated. Chemical interactions were studied by means of Fourier transform infrared spectroscopy and scanning electron microscopy was used to verify the presence of natamycin and nanohydrogel particles in the film matrix. The results show that natamycin and natamycin-loaded poly(N-isopropylacrylamide) (PNIPA) nanohydrogels can be successfully added to edible films without changing their main packaging properties. However, tensile strength decreased (p < 0.05) when both natamycin and natamycin-loaded PNIPA nanohydrogels were incorporated (from 24.44 to 17.02 and 16.63 MPa, for GA-NA and GA-PNIPA, respectively). GA-NA and GA-PNIPA films are more opaque and showed to be more sensitive to water (i.e. higher values of moisture content and decrease of contact angle) than GA films. Scanning electron microscopy images confirmed the presence of natamycin and poly(N-isopropylacrylamide) nanohydrogels in the films’ matrix. Since natamycin could be successfully released from polysaccharide-based films, the system could be used as active packaging ingredient when used free in the matrix or as smart packing when loaded with PNIPA nanohydrogels.

/pdf/development-of-active-and-nanotechnology-based-smart-edible-ig853z1njd.pdf

Development of Active and Nanotechnology-based Smart Edible Packaging Systems: Physical–chemical Characterization

Natamycin is an antifungal polyene macrolide antibiotic with wide applications in health and food industries. Currently, it is the only antifungal food additive with the GRAS status (Generally Regarded as Safe). Natamycin production was investigated under the effect of different initial glucose concentrations. Maximal antibiotic production (1.58 ± 0.032 g/L) was achieved at 20 g/L glucose. Under glucose limitation, natamycin production was retarded and the produced antibiotic was degraded. Higher glucose concentrations resulted in carbon catabolite repression. Secondly, intermittent feeding of glucose improved natamycin production due to overcoming glucose catabolite regulation, and moreover it was superior to glucose-beef mixture feeding, which overcomes catabolite regulation, but increased cell growth on the expense of natamycin production. Finally, the process was optimized in 7.5 L stirred tank bioreactor under batch and fed-batch conditions. Continuous glucose feeding for 30 h increased volumetric natamycin production by about 1.6- and 1.72-folds in than the batch cultivation in bioreactor and shake-flasks, respectively. Glucose is a crucial substrate that significantly affects the production of natamycin, and its slow feeding is recommended to alleviate the effects of carbon catabolite regulation as well as to prevent product degradation under carbon source limitation. Cultivation in bioreactor under glucose feeding increased maximal volumetric enzyme production by about 72% from the initial starting conditions.

/pdf/enhanced-natamycin-production-by-streptomyces-natalensis-in-ftgqpi0rdh.pdf

Enhanced Natamycin production by Streptomyces natalensis in shake-flasks and stirred tank bioreactor under batch and fed-batch conditions

Microorganisms can be used as active substances as part of biological control, and therefore are referred to as Microbial Pest Control Agents (MPCAs). MPCAs which are authorised for use are listed in Regulation (EU) No 540/2011 in accordance with EU legislation. This study focused on authorised MPCAs and also those for which a decision on completeness has been taken in accordance with Article 6(3) of Directive 91/414 EEC. In this report we provide an extensive review of the scientific literature relevant for the evaluation of the environmental hazards and risks posed by MPCAs based on knowledge on their effects on the environment. Six topics were investigated in detail, including: MPCA genetic stability and transfer, interference with the system for drinking water quality control, fate and behaviour in the environment, ability to produce metabolites and potential toxic effects on non-target organisms, host specificity and potential effect on non-target organisms and, finally, the appropriateness of existing test guidelines for risk assessment. The effects of biotic and abiotic factors on growth, survival and pathogenicity of MPCAs have also been evaluated, as well as the potential of extrapolation – or read acrossbetween species/strain/isolates not used as MPCAs. A systematic literature search was run on five search engines and more than 2123 publications were retrieved which were considered relevant for the analysis. The distribution of the literature per topic was heterogeneous, ranging from 2 to 447, showing that there is a clear need of further research in particular areas, most notably on the capacity of MPCAS to interfere with drinking water quality control systems. The retrieved material was exported and classified into a dedicated database which facilitated subsequent analysis. This report details the methods used in the study and presents the results in the form of six mini-reviews, one for each of the topics mentioned above.

https://efsa.onlinelibrary.wiley.com/doi/pdf/10.2903/sp.efsa.2013.EN-518

Scientific support, literature review and data collection and analysis for risk assessment on microbial organisms used as active substance in plant protection products –Lot 1 Environmental Risk characterisation

During last decades, study on the development of eco-friendly processes for the production of selenium nanoparticles (Se NPs) have received much attention due to hazardous effects of chemical compounds used for nanoparticle preparation. The present study was designed to screen actinomycete strains able to produce Se NPs. Among isolated bacterial strains, a terrestrial actinomycete strain which was tolerant to Se4+ ions (200 μg/ml of) was launched as Se NPs producer. Morphological and biochemical characteristics as well as 16S rDNA gene analysis of the selected strain introduced it as Streptomyces microflavus strain FSHJ31. The biologically synthesized Se NPs was then purified using n-Octyl alcohol/water extraction system and characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR) techniques. Analysis of the particle size distribution pattern of biogenic Se NPs via laser light scattering method demonstrated the size range of 28–123 nm for Se NPs with the 48 nm NPs being the most frequent particles.

https://www.rroij.com/open-access/biosynthesis-and-characterization-of-selenium-nanoparticles-produced-by-terrestrial-act-47-52.pdf

Biosynthesis and Characterization of Selenium Nanoparticles Produced by Terrestrial Actinomycete Streptomyces microflavus Strain FSHJ31.

Streptomyces genus as a source of probiotics and its potential for its use in health.

https://cyberleninka.org/article/n/1180676.pdf

Biochemical studies on the Natamycin antibiotic produced by Streptomyces lydicus: Fermentation, extraction and biological activities

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Biochemical studies on the Natamycin antibiotic produced by Streptomyces lydicus: Fermentation, extraction and biological activities