Antimicrobial and Gas Barrier Crustaceans and Fungal Chitin-Based Coatings on Biodegradable Bioplastic Films.

Chitin nanofibrils (CN) can be obtained from crustaceans and fungal sources and can be used for preparing coatings for bioplastic films, that are fundamental for developing a safe and sustainable biodegradable food packaging. Coatings with different concentrations of CN from shrimps were applied on different bioplastic substrates, like Poly (butylene succinate-co-adipate)/Poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PBSA/PHBV) blend, Polybutylene succinate (PBS), and Polybutylene adipate terephthalate/Poly(lactic acid) (PBAT/PLA) blend, but the adhesion to the substrates was scarce. On the contrary, the fungal-based CN showed a better adhesion. Additionally, it was found that the use of an additive based on oligomeric lactic acid was useful to prepare a coating with an improved adhesion to bioplastics. The gas barrier properties to oxygen and water vapour of coated and un-coated films were measured, revealing an improvement of these properties thanks to applied coatings, especially towards the oxygen. Antimicrobial properties and biodegradation capacity were also evaluated revealing an antibacterial effect of the coatings that did not significantly interfere with their biodegradability. The results are discussed and interpreted considering the correlation between composition and macromolecular structures with the observed functional properties.

Influence of Functional Bio-Based Coatings Including Chitin Nanofibrils or Polyphenols on Mechanical Properties of Paper Tissues.

The paper tissue industry is a constantly evolving sector that supplies markets that require products with different specific properties. In order to meet the demand of functional properties, ensuring a green approach at the same time, research on bio-coatings has been very active in recent decades. The attention dedicated to research on functional properties has not been given to the study of the morphological and mechanical properties of the final products. This paper studied the effect of two representative bio-based coatings on paper tissue. Coatings based on chitin nanofibrils or polyphenols were sprayed on paper tissues to provide them, respectively, with antibacterial and antioxidant activity. The chemical structure of the obtained samples was preliminarily compared by ATR-FTIR before and after their application. Coatings were applied on paper tissues and, after drying, their homogeneity was investigated by ATR-FTIR on different surface areas. Antimicrobial and antioxidant properties were found for chitin nanofibrils- and polyphenols-treated paper tissues, respectively. The mechanical properties of treated and untreated paper tissues were studied, considering as a reference the same tissue paper sample treated only with water. Different mechanical tests were performed on tissues, including penetration, tensile, and tearing tests in two perpendicular directions, to consider the anisotropy of the produced tissues for industrial applications. The morphology of uncoated and coated paper tissues was analysed by field emission scanning electron microscopy. Results from mechanical properties evidenced a correlation between morphological and mechanical changes. The addition of polyphenols resulted in a reduction in mechanical resistance, while the addition of chitin enhanced this property. This study evidenced the different effects produced by two novel coatings on paper tissues for personal care in terms of properties and structure.

Liquid and Solid Functional Bio-Based Coatings.

The development of new bio-based coating materials to be applied on cellulosic and plastic based substrates, with improved performances compared to currently available products and at the same time with improved sustainable end of life options, is a challenge of our times. Enabling cellulose or bioplastics with proper functional coatings, based on biopolymer and functional materials deriving from agro-food waste streams, will improve their performance, allowing them to effectively replace fossil products in the personal care, tableware and food packaging sectors. To achieve these challenging objectives some molecules can be used in wet or solid coating formulations, e.g., cutin as a hydrophobic water- and grease-repellent coating, polysaccharides such as chitosan-chitin as an antimicrobial coating, and proteins as a gas barrier. This review collects the available knowledge on functional coatings with a focus on the raw materials used and methods of dispersion/application. It considers, in addition, the correlation with the desired final properties of the applied coatings, thus discussing their potential.

Electrosprayed Shrimp and Mushroom Nanochitins on Cellulose Tissue for Skin Contact Application.

Cosmetics has recently focused on biobased skin-compatible materials. Materials from natural sources can be used to produce more sustainable skin contact products with enhanced bioactivity. Surface functionalization using natural-based nano/microparticles is thus a subject of study, aimed at better understanding the skin compatibility of many biopolymers also deriving from biowaste. This research investigated electrospray as a method for surface modification of cellulose tissues with chitin nanofibrils (CNs) using two different sources-namely, vegetable (i.e., from fungi), and animal (from crustaceans)-and different solvent systems to obtain a biobased and skin-compatible product. The surface of cellulose tissues was uniformly decorated with electrosprayed CNs. Biological analysis revealed that all treated samples were suitable for skin applications since human dermal keratinocytes (i.e., HaCaT cells) successfully adhered to the processed tissues and were viable after being in contact with released substances in culture media. These results indicate that the use of solvents did not affect the final cytocompatibility due to their effective evaporation during the electrospray process. Such treatments did not also affect the characteristics of cellulose; in addition, they showed promising anti-inflammatory and indirect antimicrobial activity toward dermal keratinocytes in vitro. Specifically, cellulosic substrates decorated with nanochitins from shrimp showed strong immunomodulatory activity by first upregulating then downregulating the pro-inflammatory cytokines, whereas nanochitins from mushrooms displayed an overall anti-inflammatory activity via a slight decrement of the pro-inflammatory cytokines and increment of the anti-inflammatory marker. Electrospray could represent a green method for surface modification of sustainable and biofunctional skincare products.

Biomimetic hydrogel by enzymatic crosslinking of pullulan grafted with ferulic acid.

A novel eco-friendly two-step synthesis process of neutral pullulan (PUL)-ferulic acid (FA) conjugates was reported in this work. Ferulic acid was first transformed to activated ferulate-imidazolide using N,N'-carbonyldiimidazole (CDI), a green activated reagent. Issued product was then reacted with pullulan. PUL-FA derivatives were characterized by FTIR and 1H NMR leading to substitution degrees (DS) between 0.02 and 0.1 (mol FA per mol PUL repeat unit). The study in dilute regime indicated an associative behavior with the presence of aggregate structures in solution due to the hydrophobic interactions between the grafted FA onto polysaccharide backbones. Laccase from Trametes versicolor was then used to crosslink polysaccharide chains to obtain biomimetic PUL-FA hydrogels. Gelling's kinetics were analyzed with rheology in dynamic mode showing the impact of laccase amount, DS and concentration. Mechanical and swelling properties appear related only to DS and concentration of PUL-FA products.

Enzymatic cross-linking of carboxymethylpullulan grafted with ferulic acid.

Carboxymethylpullulan (CMP) has been modified in a two-step grafting reaction of ferulic acid (FA). Acid adipic dihydrazyde (ADH) was first reacted with FA activated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC). Then the product of this first reaction was reacted with CMP (activated with EDC). Grafted polysaccharides structure was confirmed by FTIR and (1)H NMR spectroscopy. Analyses by size-exclusion chromatography (SEC) coupling on-line with a multi-angle light scattering detector (MALS), a viscometer and a differential refractive index detector (DRI) (SEC/MALS/DRI/Visco) showed that associations between FA moieties occurred due to hydrophobic interactions. The grafting rates of FA were determined by the Folin-Ciocalteu method and were found between 1.0% and 11.2% (mol/mol anhydroglucose unit). The CMP-FA were then enzymatically cross-linked with laccase from Pleurotus ostreatus. The crosslinking reactions were followed by rheological measurements, demonstrating the influence of laccase concentration on kinetics. Elastic modulus and swelling rates of hydrogels depends on FA content only for low values.