1. Improving bacterial cellulose films by ex-situ and in-situ modifications: a reviewPatricia Cazón, Manuel Vazquez, 2021, review article Abstract: The high intake of plastic materials for food packaging causes environmental problems due to the nonbiodegradable properties of these materials. High, low and very low-density polyethylene, polyethylene terephthalate, polyvinyl chloride, polystyrene and polypropylene are the main materials used. Biodegradable
polymers from natural sources are potential raw materials to develop novel food packaging. Bacterial cellulose is a material with extraordinary properties that is gaining special interest for applications in the Food Industry. The excellent mechanical properties, thermal stability and barrier to water vapor, oxygen and UV radiation of bacterial cellulose compared to other polysaccharides make this material very attractive and a potential alternative to non-biodegradable synthetic materials. Nevertheless, bacterial cellulose films are limited due to their lower elasticity. Therefore, the aim of this review is to provide an overview of the ex-situ and in-situ modifications of bacterial cellulose to improve its properties for the development of films for food packaging.
Found in: ključnih besedah
Keywords: Bacterial cellulose, In-situ modifications, Ex-situ modifications, Food packaging.
Published: 09.12.2020; Views: 1607; Downloads: 0
 Fulltext (1,90 MB) |
2. UV-protecting films based on bacterial cellulose, glycerol and polyvinyl alcohol: effect of water activity on barrier, mechanical and optical propertiesManuel Vazquez, Gonzalo Velazquez, Patricia Cazón, 2020, original scientific article Abstract: Biodegradable films based on bacterial cellulose, glycerol and polyvinyl alcohol are a new alternative to develop food packaging with the capac- ity to retard or inhibit the effect of UV radiation. However, these compounds are sensitive to moisture. Therefore, the purpose of this study was to evaluate the modifications of the mechanical, water vapor permeability and optical properties of these composite films depending on their water activity. Results showed that water molecules acted as a plasticizer
agent, modifying the mechanical, water vapor perme- ability and optical properties of the developed films. However, an overplastification process took place at higher activity water, resulting in a weakness of film structure and decreasing drastically the elongation. The transmittance in the UV–VIS light region decreased when the activity water increased. No significant variations were observed in color, trans- parency or opacity properties.
Found in: ključnih besedah
Keywords: GAB model, Moisture adsorption isotherms, Plasticization, Bacterial cellulose, Mechanical properties, UV-barrier properties
Published: 09.12.2020; Views: 1666; Downloads: 80
Fulltext (552,03 KB) |
3. Environmentally Friendly Films Combining Bacterial Cellulose, Chitosan, and Polyvinyl Alcohol: Effect of Water Activity on Barrier, Mechanical, and Optical PropertiesGonzalo Velazquez, Manuel Vazquez, Patricia Cazón, 2019, original scientific article Abstract: The interest in developing new materials intended for food packaging based on bacterial cellulose is growing in the recent years. Flexible and transparent films from bacterial cellulose-chitosan-polyvinyl alcohol have shown excellent UV-barrier properties. However, this composite material interacts with ambient moisture modifying its water activity due to its hydrophilic nature. In this work, an extensive study was carried out to evaluate the changes in the properties of these films as a function of water activity. Moisture adsorption isotherm were described by the GAB method. Results showed the plasticizing effect of water molecules increasing the water vapour permeability of the samples from 1.86·10-12 to 1.17·10-11 g/m·s·Pa, the percentage of elongation from 3.25 to 36.55% and the distance to burst from 0.64 to 5.12 mm. The increase of the water activity dropped the tensile strength values from 74.76 to 38.56 MPa, Young’s modulus values from 3133.46 to 30.71 MPa and burst strength to 703.87 g. The values of the UV-barrier were maintained at the wide range of water activity. Consequently, water molecules do not affect the UV-barrier properties of the films.
Found in: ključnih besedah
Keywords: GAB model, moisture adsorption isotherms, plasticization, bacterial cellulose, mechanical properties, UV-barrier properties, moisture content
Published: 09.12.2020; Views: 1633; Downloads: 0
Fulltext (483,23 KB) |
4. Bacterial cellulose films: Evaluation of the water interactionManuel Vazquez, Gonzalo Velazquez, Patricia Cazón, 2020, original scientific article Abstract: Bacterial cellulose is a biopolymer that is gaining attention due to its 3D structure, higher purity, porosity and surface area. However, this material can interact with water molecules from the surrounding environment, resulting in alterations of its properties. Hence, the purpose of this study was to analyze the modifications on the mechanical, water vapor permeability and optical properties of bacterial cellulose films as a function of the water activity. Results indicated that water acted as a plasticizer, mainly affecting mechanical and water vapor permeability properties. The moisture adsorption isotherms allowed predicting the moisture content of the bacterial cellulose films at several relative humidity conditions. Values for tensile strength and burst strength ranged from 15.50 to 22.28 MPa and from 145.03–338.10 g, respectively. The elongation and the distance to burst ranged from 1.36 to 3.71 % and from 0.39 to 1.86 mm, respectively. These values increased due to the plasticizing effect of the water molecules. Water vapor permeability values ranged from 1.35·10−12 to 3.13·10-11 g/ m s Pa, showing a significant increase up to 0.48 of water activity. Bacterial cellulose films showed excellent UV-barrier properties in the different water activities evaluated.
Found in: ključnih besedah
Keywords: GAB model, Moisture adsorption isotherms, Bacterial cellulose, Mechanical properties, UV-barrier properties
Published: 09.12.2020; Views: 1645; Downloads: 0
Fulltext (1,02 MB) |
5. |
6. Purification-independent immunoreagents obtained by displaying nanobodies on bacteria surfaceSandra Oloketuyi, Carina Dilkaute, Elisa Mazzega, Joachim Jose, Ario De Marco, 2019, original scientific article Found in: ključnih besedah
Summary of found: ... Bacterial display, immunocapture, diagnostics, nanobodies...
Keywords: Bacterial display, immunocapture, diagnostics, nanobodies
Published: 18.04.2019; Views: 2186; Downloads: 0
Fulltext (1,44 MB) |
7. Regional biodiversity and seasonal dynamics of the bacterial communities in karstic springs of SloveniaMaja Opalički Slabe, 2019, doctoral dissertation Abstract: Information on groundwater’s natural bacterial communities is important for evaluating pristine groundwater’s quality, as environmental changes potentially lead to alterations in bacterial community structures. In four seasons, 15 hypothetically pristine springs across five karst eco-regions in Slovenia (Central Europe) were analysed during their low discharge, and their basic physical and chemical parameters were recorded. The diversity of bacterial community structures was assessed with a terminal restriction fragment length polymorphism fingerprinting method. Total cell counts as bacterial abundance and electron transport system activity as bacterial respiratory activity were used for quantitative evaluation of bacterial communities. To detect anthropogenic pollution, spring water was tested by the cultivation of coliform bacteria and Escherichia coli (E. coli).
Results indicate distinct regional differences in environmental parameters, bacterial respiratory activity, presence of coliforms and E. coli, bacterial abundances, and qualitative bacterial community structures, but there were no regional differences in the numbers of operational taxonomic units and biodiversity indices (Shannon-Wiener’s and Simpson’s diversity index, Buzas and Gibson’s evenness). The analysis of seasonal environmental parameters showed significant differences in dissolved organic carbon and pH, and also significant changes in bacterial respiratory activity and abundances, as well as differences in bacterial community structures, the numbers of operational taxonomic units, and biodiversity indices. No seasonal variations were shown for coliforms and E. coli.
Despite seasonal oscillations, regional differences prevailed among five karst eco-regions and indicate a significant influence on the qualitative and quantitative aspects of groundwater bacterial community structures. The study confirmed both regional and seasonal differences in groundwater bacterial community structures, which should be included in further sustainable management plans of the aquifers.
Found in: ključnih besedah
Keywords: karst springs, bacterial community structure (BCS), terminal restriction fragment length polymorphism (T-RFLP), total cell counts (TCC), electron transport system activity (ETSA)
Published: 26.06.2019; Views: 2850; Downloads: 151
Fulltext (3,76 MB) |
8. Characterization of bacterial cellulose films combined with chitosan and polyvinyl alcohol: Evaluation of mechanical and barrier propertiesManuel Vazquez, Gonzalo Velazquez, Patricia Cazón, 2019, original scientific article Abstract: Bacterial cellulose (BC) produced by Komagataeibacter xylinus is a biomaterial with a unique three-dimensional structure. To improve the mechanical properties and reinforce the BC films, they were immersed in polyvinyl alcohol (0–4%) and chitosan (0–1%) baths. Moisture content, mechanical properties and water vapour perme- ability were measured to assess the effect of polyvinyl alcohol and chitosan. The morphology, optical, structural and thermal properties were evaluated by scanning electron microscopy, spectral analysis, thermogravimetry and differential scanning calorimetry. Results showed that moisture content was significantly affected by the chitosan presence. Tensile strength values in the 20.76–41.65 MPa range were similar to those of synthetic polymer films. Percentage of elongation ranged from 2.28 to 21.82% and Young's modulus ranged from 1043.88 to 2247.82 MPa. The water vapour permeability (1.47×10−11–3.40×10−11 g/m s Pa) decreased with the addition of polyvinyl alcohol. The developed films own UV light barrier properties and optimal visual appearance.
Found in: ključnih besedah
Keywords: Films, Bacterial cellulose, Water vapor permeability, Chitosan, Polyvinyl alcohol, UV protection
Published: 14.12.2020; Views: 1510; Downloads: 0
Fulltext (1,78 MB)
This document has many files! More...
|
9. The microbial diversity of a storm cloud as assessed by hailstonesNiels Woetmann Nilesen, Bjarne Munk Hansen, Kai Finster, Tina Šantl Temkiv, Ulrich Gosewinkel Karlson, 2012, original scientific article Found in: ključnih besedah
Summary of found: ...cloud-borne bacteria, bacterial diversity, species richness, species evenness, atmospheric chemistry,...
Keywords: cloud-borne bacteria, bacterial diversity, species richness, species evenness, atmospheric chemistry, biogeography
Published: 04.01.2021; Views: 1620; Downloads: 0
Fulltext (194,35 KB) |
10. On the usage of classical nucleation theory in quantification of the impact of bacterial INP on weather and climateMaher Sahyoun, Heike Wex, Ulrich Karlson Gosewinkel, Tina Šantl Temkiv, Niels Woetman Nielsen, Kai Finster, Jens H. Sørensen, Frank Stratmann, Ulrik S. Korsholm, 2016, original scientific article Found in: ključnih besedah
Keywords: Ice nucleation, Bacterial INP, Ice nucleation active proteins, Classical nucleation theory, Ice nucleation rate
Published: 04.01.2021; Views: 1777; Downloads: 0
Fulltext (1,34 MB) |
