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Electro-hydrodynamic processing, comprising electrospraying and electrospinning techniques, has emerged as a versatile technology to produce nanostructured fiber-based and particle-based materials. In this work, an antimicrobial active multilayer system comprising a commercial polyhydroxyalkanoate substrate (PHA) and an electrospun PHA coating containing in situ-stabilized silver nanoparticles (AgNPs) was successfully developed and characterized in terms of morphology, thermal, mechanical, and barrier properties. The obtained materials reduced the bacterial population of Salmonella enterica below the detection limits at very low silver loading of 0.002 ± 0.0005 wt %. As a result, this study provides an innovative route to generate fully renewable and biodegradable materials that could prevent microbial outbreaks in food packages and food contact surfaces. ; This work was financially supported by the Spanish Ministry of Economy and Competitiveness (AGL2015-63855-C2-1-R). Jinneth Lorena Castro-Mayorga is supported by the Administrative Department of Science, Technology and Innovation (Colciencias) of the Colombian Government. Maria Jose Fabra is recipient of a Ramon y Cajal contract from the Spanish Ministry of Economy and Competitiveness. Maria Reis from Universidade Nova de Lisboa, Lisbon, Portugal is acknowledged for supplying the PHBV18 material.

Electro-hydrodynamic processing, comprising electrospraying and electrospinning techniques, has emerged as a versatile technology to produce nanostructured fiber-based and particle-based materials. In this work, an antimicrobial active multilayer system comprising a commercial polyhydroxyalkanoate substrate (PHA) and an electrospun PHA coating containing in situ-stabilized silver nanoparticles (AgNPs) was successfully developed and characterized in terms of morphology, thermal, mechanical, and barrier properties. The obtained materials reduced the bacterial population of Salmonella enterica below the detection limits at very low silver loading of 0.002 ± 0.0005 wt %. As a result, this study provides an innovative route to generate fully renewable and biodegradable materials that could prevent microbial outbreaks in food packages and food contact surfaces. ; This work was financially supported by the Spanish Ministry of Economy and Competitiveness (AGL2015-63855-C2-1-R). Jinneth Lorena Castro-Mayorga is supported by the Administrative Department of Science, Technology and Innovation (Colciencias) of the Colombian Government. Maria Jose Fabra is recipient of a Ramon y Cajal contract from the Spanish Ministry of Economy and Competitiveness. Maria Reis from Universidade Nova de Lisboa, Lisbon, Portugal is acknowledged for supplying the PHBV18 material. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).

This study deals with the optimization and scaling up of the production of poly(3-hydroxybutyrate), PHB, nanocomposites containing biosynthesized silver nanoparticles (AgNPs) to generate materials with antimicrobial performance. First, a comparative study of the chemical and biological synthesis of AgNPs during the fermentation process of Cupriavidus necator at shake flask-scale was carried out. These experiments demonstrated the inherent capacity of C. necator to reduce the silver salt and produce AgNPs without the need for adding a reducing agent and, that the method of synthesis (with or without reducing agent) affects the dispersion of the AgNPs and their antimicrobial performance. Finally, the process was scaled-up to a 10 Liters bioreactor and the relevant physical properties of the PHB-AgNPs nanocomposites pressed into films were determined. From the characterization work, the AgNPs were found to be well dispersed and distributed into the polymer matrix, having a maximum frequency of particles with average diameter of 76–95 nm. Moreover, the presence of AgNPs did not cause any effect on the thermal properties of the biopolymer, although a slight reduction in crystallinity was seen. The developed materials presented a strong antimicrobial activity against the food-borne pathogens Salmonella enterica and Listeria monocytogenes, which makes them potentially suitable for active coatings and packaging applications. Complete biodisintegration of the samples occurred during composting conditions within the first 40 days. Interestingly, the presence of the AgNPs did not impair the profile of biodegradation of the microbial polymer. ; The authors would like to thank to the Active and intelligent fibre-based packaging – innovation and market introduction (ActInPak) COST Action FP1405 for the funding of the Short Therm Scientific Mission, to Octavio Cedenilla from the Instituto de Ciencias Agrarias-CSIC for the ICP-OES analysis and to Dr. Luis Cabedo, from Universitat Jaume I for his support with WAXD analyses and biodisintegration tests. Research leading to these results has received funding from the Comunidad de Madrid (P2013/MIT2807) and the Spanish Ministry of Economy and Competitiveness, (BIO2013-44878-R and AGL2015-63855-C2-1-R). Jinneth Lorena Castro-Mayorga is supported by the Administrative Department of Science, Technology and Innovation (Colciencias) of the Colombian Government. ; Peer reviewed

31 p.-9 fig.-3 tab. ; This study deals with the optimization and scaling up of the production of poly(3-hydroxybutyrate), PHB, nanocomposites containing biosynthesized silver nanoparticles (AgNPs) to generate materials with antimicrobial performance. First, a comparative study of the chemical and biological synthesis of AgNPs during the fermentation process of Cupriavidus necator at shake flask-scale was carried out. These experiments demonstrated the inherent capacity of C. necator to reduce the silver salt and produce AgNPs without the need for adding a reducing agent and, that the method of synthesis (with or without reducing agent) affects the dispersion of the AgNPs and their antimicrobial performance. Finally, the process was scaled-up to a 10Liters bioreactor and the relevant physical properties of the PHB-AgNPs nanocomposites pressed into films were determined. From the characterization work, the AgNPs were found to be well dispersed and distributed into the polymer matrix, having a maximum frequency of particles with average diameter of 76-95nm. Moreover, the presence of AgNPs did not cause any effect on the thermal properties of the biopolymer, although a slight reduction in crystallinity was seen. The developed materials presented a strong antimicrobial activity against the food-borne pathogens Salmonella enterica and Listeria monocytogenes, which makes them potentially suitable for active coatings and packaging applications. Complete biodisintegration of the samples occurred during composting conditions within the first 40days. Interestingly, the presence of the AgNPs did not impair the profile of biodegradation of the microbial polymer. ; The authors would like to thank to the Active and intelligent fibre-based packaging - innovation and market introduction (ActInPak) COST Action FP1405 for the funding of the Short Therm Scientific Mission, to Octavio Cedenilla from the Instituto de Ciencias Agrarias-CSIC for the ICP-OES analysis and to Dr. Luis Cabedo, from Universitat Jaume I for his support with mechanical testing, WAXD analyses and biodisintegration tests.Research leading to these results has received funding from the Comunidad de Madrid (P2013/MIT2807) and the Spanish Ministerio de Economía y Competitividad, (BIO2013-44878-R and AGL2015-63855-C2-1-R). Jinneth Lorena Castro-Mayorga is supported by the Administrative Department of Science, Technology and Innovation (Colciencias) of the Colombian Government. ; Peer reviewed

In this work, zinc oxide (ZnO) micron and nano sized-particles with different morphologies were synthesized by aqueous precipitation and evaluated as antimicrobial agents against foodborne pathogens. The most effective bactericide system was selected to prepare active poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films by three different methods (i) direct melt-mixing, (ii) melt-mixing of preincorporated ZnO into PHBV18 (18 mol% valerate content) fiber mats made by electrospinning, and, (iii) as a coating of the annealed electrospun PHBV18/ZnO fiber mats over compression molded PHBV. Results showed that ZnO successfully improved the thermal stability of the PHBV18, being the preincorporation method the most efficient in mitigating the negative impact that the PHBV18 had on the thermal stability, barrier and optical properties of the PHBV films. Similar behavior was found for the coating structure although this film showed effective and prolonged antibacterial activity against Listeria monocytogenes. This study highlights the suitability of the PHBV/ZnO nanostructures for active food packaging and food contact surface applications. ; This work was financially supported by the Spanish Ministry of Economy and Competitiveness (MAT2012-38947-C02-01 and AGL2015-63855-C2-1-R). J.L. Castro-Mayorga is supported by the Administrative Department of Science, Technology and Innovation (Colciencias) of Colombian Government. M. J. Fabra is recipient of a Ramon y Cajal contract from the Spanish Ministry of Economy and Competitiveness. ; Peer reviewed

Active biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) melt mixed nanocomposites and bilayer structures containing copper oxide (CuO) nanoparticles were developed and characterized. The bilayer structures consisted of a bottom layer of compression molded PHBV3 (3% mol valerate) coated with an active electrospun fibers mat made with CuO nanoparticles and PHBV18 (18% valerate) derived from microbial mixed cultures and cheese whey. The results showed that the water vapor permeability increased with the CuO addition while the oxygen barrier properties were slightly enhanced by the addition of 0.05 wt % CuO nanoparticles to nanocomposite films but a negligible effect was registered for the bilayer structures. However, the mechanical properties were modified by the addition of CuO nanoparticles. Interestingly, by incorporating highly dispersed and distributed CuO nanoparticles in a coating by electrospinning, a lower metal oxide loading was required to exhibit significant bactericidal and virucidal performance against the food-borne pathogens Salmonella enterica, Listeria monocytogenes, and murine norovirus. The biodisintegration tests of the samples under composting conditions showed that even the 0.05% CuO-coated structures biodegraded within 35 days. ; This work was financially supported by the Spanish Ministry of Economy and Competitiveness (project AGL2015–63855-C2–1-R). J.L.C.-M. is supported by the Administrative Department of Science, Technology and Innovation (Colciencias) of Colombian Government. M.J.F. is recipient of a Ramon y Cajal contract from the Spanish Ministry of Economy and Competitiveness. ; Peer reviewed

Silver nanoparticles (AgNP) have strong broad-spectrum antimicrobial activity and gained increased attention for the development of AgNP based products, including medical and food applications. Initially, the efficacy of AgNP and silver nitrate (AgNO3) was evaluated for inactivating norovirus surrogates, the feline calicivirus (FCV) and the murine norovirus (MNV). These norovirus surrogates were exposed to AgNO3 and AgNP solutions for 24 h at 25 °C and then analyzed by cell-culture assays. Both AgNP and silver ions significantly decreased FCV and MNV infectivity in a dose-dependent manner between concentrations of 2.1 and 21 mg/L. Furthermore, poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films were prepared by depositing a coating of thermally post-processed electrospun PHBV18/AgNP fiber mats over compression moulded PHBV3 films. After 24 h exposure at 37 °C and 100% RH, no infectious FCV were recovered when in contact with the AgNP films while MNV titers decreased by 0.86 log. The morphology of the PHBV18 and PHBV18/AgNP fibers studied by SEM showed smooth and continuous fibers in both cases and the EDAX analysis confirmed the homogeneously distribution of AgNP into the coating and onto the PHBV3/PHBV18 layer. This study showed, for the first time, the suitability of the PHBV18/AgNP electrospun coating for antiviral surfaces. ; This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) (RYC-2012-09950, RYC-2014-158, AGL2015-63855-C2-1-R and INIA grant RTA2014-00024-C04-03). GS and MJF were supported by the "Ramón y Cajal" Young Investigator from the MINECO (RYC-2012-09950 and RYC-2014-15842). JLC-M was supported by the Administrative Department of Science, Technology and Innovation (Colciencias) of Colombian Government. ; Peer reviewed

In this work, three active bio-based multilayer structures, using a polyhydroxybutyrate-co-valerate film with a valerate content of 8 % (PHBV8) as support, were developed. To this end, a zein interlayer with or without cinnamaldehyde (CNMA) was directly electrospun onto one side of the PHBV8 film and the following systems were developed: (1) without an outer layer; (2) using a PHBV8 film as outer layer; and (3) using an alginate-based film as outer layer. These multilayer structures were characterized in terms of water vapour and oxygen permeabilities, transparency, intermolecular arrangement and thermal properties. The antimicrobial activity of the active bio-based multilayer systems and the release of CNMA in a food simulant were also evaluated. Results showed that the presence of different outer layers reduced the transport properties and transparency of the multilayer films. The active bio-based multilayer systems showed antibacterial activity against Listeria monocytogenes being the multilayer structure prepared with CNMA and PHBV outer layers (PHBV + zein/CNMA + PHBV) the one that showed the greater antibacterial activity. The release of CNMA depended on the multilayer structures, where both Fick's and Case II transport-polymer relaxation explained the release of CNMA from the multilayer systems. ; Acknowledgments: Miguel A. Cerqueira (SFRH/BPD/72753/2010) andAnaI.Bourbon(SFRH/BD/73178/2010)arerecipientofafellowship from the Fundação para a Ciência e Tecnologia (FCT, POPH-QREN and FSE Portugal). J.L. Castro-Mayorga is supported by the Administrative Department of Science, Technology and Innovation (Colciencias) of Colombian Government. M. J. Fabra is a recipient of a Ramon y Cajal contract (RyC-2014-158) from the Spanish Ministry of Economy and Competitiveness. This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and of the Project RECI/BBB-EBI/ 0179/2012 ...

Cinnamaldehyde (CNMA), an organic compound that gives cinnamon its flavor and odor, was investigated for its virucidal activity on norovirus surrogates, murine norovirus (MNV) and feline calicivirus (FCV), and hepatitis A virus (HAV). Initially, different concentrations of CNMA (0.1, 0.5 and 1 %) were individually mixed with each virus at titers of ca. 6–7 log10 TCID50/ml and incubated 2 h at 4 and 37 °C. CNMA was effective in reducing the titers of norovirus surrogates in a dose-dependent manner after 2 h at 37 °C, while HAV titers were reduced by 1 log10 after treatment with 1 % of CNMA. When incubation time was extended, HAV titers were reduced by 3.4 and 2.7 log10 after overnight incubation at 37 °C with 1 and 0.5 % of CNMA, respectively. Moreover, this paper analyzed, for the first time, the antiviral activity of adding an active electrospun interlayer based on zein and CNMA to a polyhydroxybutyrate packaging material (PHB) in a multilayer form. Biodegradable multilayer systems prepared with 2.60 mg/cm2 (~9.7 %) of CNMA completely inactivated FCV according to ISO 22196:2011, while MNV titers were reduced by 2.75 log10. When the developed multilayer films were evaluated after one month of preparation or at 25 °C, the antiviral activity was reduced as compared to freshly prepared multilayer films evaluated at 37 °C. The results show the excellent potential of this system for food contact applications as well as for active packaging technologies in order to maintain or extend food quality and safety. ; This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) (RYC-2012-09950, AGL2015-63855-C2-1 and INIA Grant RTA2014-00024-C04-03). GS was supported by the "Ramón y Cajal" Young Investigator and MJF was recipient of a Juan de la Cierva contract from the MINECO. JLC-M was supported by the Departamento Administrativo de Ciencia, Tecnología e Innovación (Colciencias) of Colombian Government and WR by the "Student Mobility for Placement e SMP" Grant of the EU Life Learning Program. ; Peer reviewed

In this work, three active bio-based multilayer structures, using a polyhydroxybutyrate-co-valerate film with a valerate content of 8 % (PHBV8) as support, were developed. To this end, a zein interlayer with or without cinnamaldehyde (CNMA) was directly electrospun onto one side of the PHBV8 film and the following systems were developed: (1) without an outer layer; (2) using a PHBV8 film as outer layer; and (3) using an alginate-based film as outer layer. These multilayer structures were characterized in terms of water vapour and oxygen permeabilities, transparency, intermolecular arrangement and thermal properties. The antimicrobial activity of the active bio-based multilayer systems and the release of CNMA in a food simulant were also evaluated. Results showed that the presence of different outer layers reduced the transport properties and transparency of the multilayer films. The active bio-based multilayer systems showed antibacterial activity against Listeria monocytogenes being the multilayer structure prepared with CNMA and PHBV outer layers (PHBV + zein/CNMA + PHBV) the one that showed the greater antibacterial activity. The release of CNMA depended on the multilayer structures, where both Fick's and Case II transport—polymer relaxation explained the release of CNMA from the multilayer systems. ; Miguel A. Cerqueira (SFRH/BPD/72753/2010) and Ana I. Bourbon (SFRH/BD/73178/2010) are recipient of a fellowship from the Fundação para a Ciência e Tecnologia (FCT, POPH-QREN and FSE Portugal). J.L. Castro-Mayorga is supported by the Administrative Department of Science, Technology and Innovation (Colciencias) of Colombian Government. M. J. Fabra is a recipient of a Ramon y Cajal contract (RyC-2014-158) from the Spanish Ministry of Economy and Competitiveness. This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and of the Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462). The support of EU Cost Action MP1206 is gratefully acknowledged. ; Peer reviewed