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Descrizione della proposta progettuale NIHAO-Ma elaborata nell'ambito del quadro della cooperazione internazionale Italia-Cina

Report di progetto: Progetto Be&Save

In this paper, physico-chemical and antimicrobial properties of films based on pectin/sodium alginate blends crosslinked by zinc ions were investigated. The polyglycerol was used as plasticizer. The blending of pectin with alginate improved properties such as tensile strength, elasticity and water vapour barrier properties, when compared to the neat pectin film. The introduction of the cross-linking points caused an appreciable change in the physical properties due to increased free volume during the cross-linking process with zinc ions. In addition, zinc-crosslinked films evidenced antimicrobial activity against pathogens: Staphylococcus aureus, Candida Albicans and Escherichia coli. Overall, the characteristics of the pectin/sodium alginate films crosslinked with zinc showed their potential interest as materials for wound dressing.

The use of plastic materials in agriculture causes the serious drawback of huge amount of wastes to be disposed of. In order to overcome this problem a new generation of biodegradable materials has been developed based on raw materials coming from renewable source. These materials retain their physical and mechanical properties during their lifetime and when they are integrated directly in the soil, the bacterial flora transforms them in carbon dioxide or methane, water and biomass. Biodegradable films can be made using natural polymers, such as starch, cellulose, chitosan, alginate and galactomannans. These materials can be obtained by means of thermoextrusion process, solvent casting and spraying technique. Mulch coatings can be realized directly in field by spraying water solutions based on natural polysaccharides, thus covering the cultivated soil with a protective thin geo-membrane. In this paper a focused overview on the formulation development, processing understanding, field performance and mechanical properties of these innovative materials for soil mulching is presented, in comparison to oil-based non renewable films. During their using time in field, the biodegradable mulches showed suitable mechanical properties if compared to the low density polyethylene films. At the end of their lifetime the biodegradable materials were shattered and buried into the soil together with plants. The film residues disposed of in the soil biodegraded in almost 1 month for the water borne coatings and in about 12 months for the biodegradable starch- based extruded films.

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The production and management of crops uses plastics for many applications (e.g., low tunnels, high tunnels, greenhouses, mulching, silage bags, hay bales, pheromone traps, coatings of fertilizers or pesticides or hormones or seeds, and nursery pots and containers for growing transplants). All these applications have led some authors to adopt the term “plasticulture” when discussing the use of plastic materials in agriculture and related industries. Unfortunately, the sustainability of this use of plastics is low, and renewability and degradability have become key words in the debate over sustainable production and utilization of plastic. Recently, researchers and the plastics industry have made strong efforts (i) to identify new biopolymers and natural additives from renewable sources that can be used in plastics production and (ii) to enhance the degradability (biological or physical) of the new ecologically sustainable materials. In the present review, we describe the main research results, current applications, patents that have been applied for in the last two decades, and future perspectives on sustainable use of plastics to support crop production.

In order to develop new eco-sustainable technologies to set up biodegradable films for agricultural activities, spray mulching coating have been planned, prepared and tested on experimental fields. The suitable polymers used to this purpose were Arabic Gums and Agarose. Cellulose fibres were added to the polymeric water solution to improve the mulching power and to increase the tensile strength of the composite; glycerol as plasticizer was added in order to improve the mechanical response of mulching coatings. On the composites sprayed and naturally aged on the soil, both in greenhouse and in open field, mechanical, water vapor transmission rate and morphological analyses were carried out; the different environment influenced the outcomes of studied properties, evidencing better results and promising perspectives for composites employed and aged under controlled atmosphere of greenhouse.

Biodegradable starch-based extruded mulching films and biodegradable sprayable water-born polysaccharides based coatings were prepared within two European Projects as an alternative to soil mulching films made of synthetic petrochemical polymers. The biodegradable mulches, both films and coatings, had appropriate mechanical and physical properties to assure their functionality throughout the crop cycle in relation to the cultivation needs, the geographical region, and the season. The useful lifetime of the biodegradable films and coatings was fully comparable with the low density polyethylene films currently in use: the biodegradable films lasted up to 9 months, the biodegradable coatings up to 6 months. They satisfy the mulching task of weed control during the crop cycle reducing solar PAR radiation reaching the mulched soil and creating a physical barrier preventing airborne weed seeds.

In this study two algal polysaccharides, alginate and agar, chitosan from chitin, and one fruit extracted polysaccharide, pectin, have been used as binders to make solid pellets to be employed in intensive crayfish farming. We examined the performance of the pellets in water and their effect on crayfish growth. The kinetics of water absorption and solute leaching of the pellets were measured for up to 24 h. Recovered liquid was analyzed for the release of particles in water by a Low Angle Laser Light Scattering Technique. The pellets were stable in water up to 24 h, although the water stability of pectin based pellets and chitosan based pellets was greater than other pellets. At the same time, crayfish feeding response to each pellet type was monitored in growth experiments by testing diets containing similar concentrations of nutrients (proteins, lipids and carbohydrates) mixed with each of the different polysaccharides. The presence of polysaccharides positively affected crayfish growth. Indeed, animals fed these pellets showed a higher percentage growth when compared to control animals. The simple methodology used for making pellets, and the encouraging results obtained in this study, could be considered suitable parameters for people interested in crayfish farming under intensive conditions. [Keywords.-- aquaculture; Cherax albidus; food pellets; polysaccharides; rheological characteristics].

Since the potentialities of applications of low molecular weight poly-γ-glutamic acid (γ-PGA) chains have been so far only partially explored, the separation of diverse molecular families of them, as well as their characterization for potential bioactivity and ability to form films, were investigated. Two different approaches based on organic solvent precipitation or on ultra- and nano-filtration membrane-based purification of inexpensive commercial material were employed to obtain size-specific γ-PGA fractions, further characterized by size exclusion chromatography equipped with a triple detector array and by ultra-high-performance liquid chromatography to assess their average molecular weight and their concentration. The γ-PGA low molecular weight fractions, purified by ultra-filtration, have been shown both to counteract the desiccation and the oxidative stress of keratinocyte monolayers. In addition, they were exploited to prepare novel hydrocolloid films by both solvent casting and thermal compression, in the presence of different concentrations of glycerol used as plasticizer. These biomaterials were characterized for their hydrophilicity, thermal and mechanical properties. The hot compression led to the attainment of less resistant but more extensible films. However, in all cases, an increase in elongation at break as a function of the glycerol content was observed. Besides, the thermal analyses of hot compressed materials demonstrated that thermal stability was increased with higher γ-PGA distribution po-lymer fractions. The obtained biomaterials might be potentially useful for applications in cosmetics and as vehicle of active molecules in the pharmaceutical field.

Cardoon, Cynara cardunculus L. represents a biorefinery crop with a great potential in the bioplastic field. This work investigates the valorization of different cardoon components into high added value products, finally recombined into novel upgraded bioplastics. Bioprocesses for Polyhydroxybutyrate (PHB) and medium-chain-length Polyhydroxyalkanoates (mcl-PHA) production were set up starting from root inulin and seed oil respectively, highlighting the effect of process conditions on polymer properties. The ternary blend, in which the PHB polymer matrix was added with mcl-PHA and epoxidized cardoon oil, evidenced a synergic effect of both additives in modulating PHB structural and thermal properties, promoted by the physical interaction occurring among the components. This proof-of concept frames the paper in the holistic approach of circular economy applied to bioplastic production.

In this work, α−costic acid (α-CA), a metabolite coming from a perennial autochthon shrub Dittrichia viscose, was used as natural additive of polylactic acid (PLA), a biodegradable thermoplastic polymer, in order to modulate its chemico-physical properties, for the achievement of a wholly biobased packaging system. It’s the first time that α−costic acid is exploited for this appealing and novel application. The investigations performed on PLA/α-CA films, evidenced strong physical interaction occurring between the polymer and α-CA, as confirmed by NMR and FTIR-ATR analyses; SEM micrographs showed a good embedding of α-CA particles inside PLA polymer matrix; GPC analysis highlighted a slight hydrolysis of polymer matrix clearly evidenced in mechanical properties. DSC analysis underlined the significant decreasing of Tg, associated with the increase of PLA chain mobility. TGA thermograms evidenced one broad degradation profile of PLA/α-CA system, accounting for the weighty physical interaction occurring between the polar groups of both polymer and plasticizer. Finally, PLA surface wettability notably enhanced by the inclusion of α-CA polar groups. In conclusion, α-CA can be considered as a promising plasticizer of PLA and a worthy modifier of its overall properties.

Cynara Cardunculus plant was used as source of seed oil. The epoxidized oil (ECO) and presscake waste fibers (CP) recovered from post-oil extraction, were recombined for developing PLA functional biocomposites, according to “zero waste” circular economy approach. Different compositions of PLA/CP and PLA/CP/ECO were prepared in form of platelets and investigated by thermal, morphological, structural and mechanical analyses. The poor interfacial adhesion between the hydrophobic PLA matrix and short, hydrophilic and randomly dispersed presscake fibers, well evidenced by morphological analysis, was responsible of PLA thermal degradation hastening, Tg decreasing and tensile properties dropping down, since no mechanical stress transfer occurred from the polymer to the dispersed phase. The inclusion of ECO slightly improved the above properties due to its mild compatibilizing action inducing a fairly tightening of the macromolecular structure. The recycling of CP waste fibers was effective in hastening the polymer biodegradation in common soil under environmental conditions. Indeed, biocomposites recovered after 90 days of soil burial tests evidenced morphological features typical of late stage PLA biodegradation, a drastic dropping down of molecular weights and a decreasing of PLA thermal stability. These experimental evidences, not detected in soil buried neat PLA, assessed that the inclusion of CP waste fibers inside PLA matrix, represented a valid route to promote a fast and easy PLA biodegradation if compared to the composting method commonly used, for which severe atmosphere conditions and specific microbial population are necessary.

Cardoon seeds oil (Cynara Cardunculus CCO) has been attracting an increasing interest in Italy for the bio-plastic industry. Cardoon is a wild robust perennial plant, native from the Mediterranean basin. The aim of this work is the preparation of biodegradable and non-toxic plasticizers by epoxidation reaction (ECO) of CCO and the study of their potential plasticizing effect in environmentally friendly polymers like poly(lactic acid) (PLA), whose drawbacks are its brittleness and lower impact resistance. The morphological analysis evidenced a well embedding of epoxidized oil inside the polymeric matrix, thus suggesting a good compatibility; the bulk analysis of the systems, by means of DSC and TGA highlighted the decrease of Tg, due to the physical interactions between the polar residues of the polymer and oils in the amorphous region of PLA and higher thermal stability of the polymer in presence of the oils; finally mechanical properties evidenced the enhancement of polymer ductility, particularly in PLA_ECO system.

Cardoon seed oil (Cynara Cardunculus) has been attracting an increasing interest in Italy for the bio-plastic industry. Cardoon is a wild robust perennial plant, native from the Mediterranean basin. Its production can reach 30–35 t/(ha year), and the dried flowers of this plant have been used since ancient times in southern Europe as vegetable rennet, to prepare high-quality traditional milk from goat and sheep. Cardoon seeds contain high oil content (25–33%), and their composition is based on mono-, di- and triglycerides [1]. The composition in fatty acids of the Cardoon oil (CO) is similar to that of the sunflower oil, around: 60.9% linoleic, 23.6% oleic, 12.1% palmitic and 3.4% stearic acid. Moreover, Cardoon does not compete for land as far as edible resources are concerned, and the related crop does not need high quality of arable land nor fertilisers/herbicide pre-treatment, differently from what happens for materials coming from sunflower or soybean [2]. CO represents an interesting potential non-food plant oil: it can be cultivated on the contaminated soils of the Campania region (Italy), i.e. the land known with the name “terra dei fuochi” (land of fires), because it very well adapts with the local climate conditions, and through a phytoremediation process it is possible to have available a suitable plant-oil otherwise not usable for the human food. The aim of this work is the preparation of biodegradable and non-toxic plasticisers by epoxidation reaction of CO and the study of their potential plasticising effect in environmentally friendly polymers like poly(lactic acid) (PLA). This aliphatic polyester, coming from plants fermented starch, is regarded as a promising alternative to some petro-based polymers due to its noteworthy mechanical properties such as tensile strength and Young’s modulus. As most of the polyesters, the main drawback of PLA that prevents some commercial applications, concerns its brittleness and lower impact resistance [3]. Over the past, the use of proper plasticisers has been shown as a valid solution to enhance its flexibility and toughness. The epoxidized soybean oil (ESO) is well recognised to be an efficient plasticiser for PVC and other plastics, in addition with the beneficial aspects derived by its biodegradable and non-toxic nature [4]. However, this edible plasticiser feedstock may raise serious issues concerning the competition with food supply and deforestation due to the massive propagation of edible plants. Therefore, the use of CO appears advantageous to prepare biodegradable plasticisers for PLA. For this purpose, in this work, after a preliminary characterization, CO has been successfully epoxidized by performic acid, in fed-batch modality. Then some blends of PLA_ECO, i.e. with different amounts of epoxidized Cardoon oil (ECO), have been prepared and characterised by thermal, mechanical and spectroscopic analysis. A final comparison with analogous blends of PLA_ESO has shown that ECO is an effective green plasticiser for PLA.

In this paper, physico-chemical, mechanical and antimicrobial properties of hydrogels based on alginate/N-succinylchitosan blends crosslinked by calcium or zinc ions containing cellulose microfibers were investigated and discussed. With respect to plain alginate hydrogels, the addition of N-succinylchitosan significantly improved properties such as swelling degree and stability in saline solution. The water vapour transmission rate confirmed that all the hydrogels were able to assure a moist wound environment. Morphological analysis showed a good embedding of fibres within the zinc crosslinked hydrogels. In addition, zinc-crosslinked hydrogels evidenced antimicrobial activity against two common skin pathogenic bacteria, Staphylococcus aureus and Escherichia coli. Cytotoxicity assays proved that the amount of zinc released is slightly over the toxic level. Overall, the characteristics of the zinc-crosslinked hydrogels showed their potential interest as materials for wound dressing.