Gabriella Santagata

From biowaste to bioresource: Effect of a lignocellulosic filler on the properties of poly(3-hydroxybutyrate)

A lignin-rich residue (LRR) obtained as a by-product from the fermentative bioethanol production process, and commercial alkali lignin (AL), were used as fillers for the preparation of bio-based blends and composites with poly(3-hydrobutyrate) (PHB). Chemical characterization of LRR demonstrated that the filler contained sugar residues. Rheological and thermal characterization of the blends demonstrated that LRR did not affect thermal stability of PHB, while AL had a strong pro-degrading effect. Addition of suitable amounts of LRR dramatically affected the rheological behavior of the polymer melt, suggesting that the additive can modify polymer processability. LRR was also a heterogeneous nucleating agent, potentially able to control the physical aging of PHB. Lower resilience and elongation at break values were found for the biocomposites, due to the poor interfacial adhesion between filler and matrix. Biodegradation behavior of the composites was qualitatively assessed by analyzing the surface of soil buried films. Significant surface degradation was observed for PHB, while the process was retarded at high filler concentration, as LRR inhibited hydrolytic and biotic polymer degradation. The reported results demonstrated the feasibility of the conversion of an agro-industrial by-product into a bio-resource in an environmentally friendly and cost-effective way.

Enhancement of poly(3-hydroxybutyrate) thermal and processing stability using a bio-waste derived additive.

Poly(3-hydroxybutyrate) (PHB) is a biodegradable polymer, whose applicability is limited by its brittleness and narrow processing window. In this study a pomace extract (EP), from the bio-waste of winery industry, was used as thermal and processing stabilizer for PHB, aimed to engineer a totally bio-based system. The results showed that EP enhanced the thermal stability of PHB, which maintained high molecular weights after processing. This evidence was in agreement with the slower decrease in viscosity over time observed by rheological tests. EP also affected the melt crystallization kinetics and the overall crystallinity extent. Finally, dynamic mechanical and tensile tests showed that EP slightly improved the polymer ductility. The results are intriguing, in view of the development of sustainable alternatives to synthetic polymer additives, thus increasing the applicability of bio-based materials. Moreover, the reported results demonstrated the feasibility of the conversion of an agro-food by-product into a bio-resource in an environmentally friendly and cost-effective way.

Enhancement of interfacial adhesion between starch and grafted poly(ε-caprolactone)

The use of a modified poly(ε-caprolactone) (gPCL) to enhance polymer miscibility in films based on thermoplastic starch (S) and poly(ε-caprolactone) is reported. PCL was functionalized by grafting with maleic anyhdride (MA) and/or glycidyl methacrylate (GMA) by reactive blending in a batch mixer. gPCL based materials were analysed in terms of their grafting degree, structural and thermal properties. Blends based on starch and PCL (wt. ratio 80:20) with including gPCL (0, 2.5 and 5wt.%), as a compatibilizer, were obtained by extrusion and compression moulding, and their structural, thermal, mechanical and barrier properties were investigated. Blends containing gPCL evidenced better interfacial adhesion between starch and PCL domains, as deduced from both structural (XRD, FTIR, SEM) and bulk properties (DSC, TGA). Moreover, grafted PCL-based compatibilizers greatly improved functional properties of S-PCL blend films, as pointed out from mechanical performance and higher barrier properties, valuable to meet the food packaging requirements.

Design of pectin-sodium alginate based films for potential healthcare application: Study of chemico-physical interactions between the components of films and assessment of their antimicrobial activity

In this study, pectin based films including different amounts of sodium alginate were prepared by casting method. All the films, with and without polyglycerol as plasticizer, were crosslinked with zinc ions in order to extend their potential functionality. The development of junction points, occurring during the crosslinking process with zinc ions, induced the increasing of free volume with following changing in chemico-physical properties of films. The inclusion of alginate in pectin based formulations improved the strength of zinc ions crosslinking network, whereas the addition of polyglycerol significantly improved mechanical performance. Finally, zinc-crosslinked films evidenced antimicrobial activity against the most common exploited pathogens: Staphylococcus Aureus, Escherichia Coli and Candida Albicans. These results suggest that zinc-crosslinked based films can be exploitable as novel bio-active biomaterials for protection and disinfection of medical devices.

Biodegradable Spray Mulching and Nursery Pots: New Frontiers for Research

Agricultural activities need plastics for many applications such as films for soil mulching and pots for plants transplanting. The use of plastic products, made of fossil raw materials, such as polystyrene, polyethylene, and polypropylene results in huge quantities of plastic wastes to be disposed of. In the past two decades, the growing environmental awareness strongly encouraged researchers and industries toward the use of biodegradable polymers for solving the plastic waste problem. Researchers have made strong efforts to identify new biopolymers coming from renewable sources as valid ecosustainable alternatives to petroleum based plastic commodities. The main research results and current applications concerning the biodegradable plastics in agriculture, such as thermo-extruded Mater-Bi and sprayable water-born polysaccharides based coatings, are described in this chapter. A lineup of biopolymers coming from raw and renewable sources, such as polysaccharides, are reported; the intrinsic chemico-physical properties of polysaccharides, responsible for the realization of dry water stable hydrogels, suitable for the formation of both soil mulching coatings and transplanting biopots, are investigated. A description of the natural additives, fillers and cellulosic fibers included in the polymeric matrices, able to enhance the mechanical performance of coatings and pots is provided, together with the outputs in the specific applications.

Preparation and characterization of polybutylene succinate (PBS) and polybutylene adipate-terephthalate (PBAT) biodegradable blends

Biodegradable polymer films based on polybutylene succinate (PBS) and polybutylene adipate terephthalate (PBAT) blends with varying weight ratios were prepared by extrusion and chill roll calendering. The films were characterized by infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), mechanical tensile tests, scanning electron microscopy (SEM), and rheology. In the blends with higher content of PBAT, PBS crystallization was inhibited. As for mechanical performance, increasing the PBS content in PBAT an increase in the stiffness and a decrease in the ductility of the blends is detected. Finally, rheological measurements evidence an increase in the viscosity of the blends with increasing the PBAT content.Biodegradable polymer films based on polybutylene succinate (PBS) and polybutylene adipate terephthalate (PBAT) blends with varying weight ratios were prepared by extrusion and chill roll calendering. The films were characterized by infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), mechanical tensile tests, scanning electron microscopy (SEM), and rheology. In the blends with higher content of PBAT, PBS crystallization was inhibited. As for mechanical performance, increasing the PBS content in PBAT an increase in the stiffness and a decrease in the ductility of the blends is detected. Finally, rheological measurements evidence an increase in the viscosity of the blends with increasing the PBAT content.

Pectin-honey coating as novel dehydrating bioactive agent for cut fruit: Enhancement of the functional properties of coated dried fruits

In this paper, a novel and sustainable process for the fruit dehydration was described. Specifically, edible coatings based on pectin and honey were prepared and used as dehydrating and antimicrobial agents of cut fruit samples, in this way promoting the fruit preservation from irreversible deteriorative processes. Pectin-honey coating was tested on apple, cantaloupe melon, mango and pineapple. The analysis were performed also on uncoated dehydrated fruits (control). The coated fruit evidenced enhanced dehydration percentage, enriched polyphenol and vitamin C contents, improved antioxidant activity and volatile molecules profile. Moreover, the antimicrobial activity against Pseudomonas and Escherichia coli was assessed. Finally, morphological analysis performed on fruit fractured surface, highlighted the formation of a non-sticky and homogeneous thin layer. These outcomes suggested that the novel fruit dehydration process, performed by using pectin-honey coating, was able to both preserve the safety and quality of dehydrated fruits, and enhance their authenticity and naturalness.

From Microbial Biopolymers to Bioplastics: Sustainable Additives for PHB Processing and Stabilization

The term biopolymers refers to a broad class of materials that derive from naturally occurring resources. Biopolymers can be obtained through extraction from biomasses, but also through chemical or biotechnological methods from raw natural substrates. They are used to produce bioplastics, which could substitute fossil fuel-derived commodities. Among them, polyhydroxyalkanoates (PHAs) are polyesters synthesized by microorganisms as energy reserve. The most important member of PHA family is poly(3-hydroxybutyrate) (PHB). PHB is mechanically similar to polypropylene, even though its thermal instability, brittleness, and stiffness hinder its applicability. Improving PHB physical properties can be achieved by blending it with natural additives or by-products of industrial processes. This work takes the form of a case study about the effects of three natural, phenol-based, and polysaccharidic compounds on PHB properties. In particular, data on blending of two PHB matrices with a grape pomace extract (EP), a lignocellulosic biomass (LC), and tannic acid (TA) are reported. The preparation and characterization of PHB compounds and the effects of the additives on processing, thermal and photooxidative stability, crystallization rate, and microbial digestion of PHB are also shown. An overall improvement of polymer processability and photostability, along with changes in crystallization rates, was observed. The study provides evidence that natural additives have the potential for promoting the transition from biopolymers to bioplastics in a sustainable way, both from an environmental and economical point of view.

Tailoring Mater‐Bi properties by the use of a biowaste‐derived additive

In this work, a polyphenol‐containing extract from winery bio‐waste (EP) has been used as additive to tailor Mater‐Bi properties. EP was able to efficiently modulate both polymer processing and mechanical, thermal and biodegradation properties. EP decreased the melt viscosity, behaved as a Mater‐Bi plasticizer and delayed the Mater‐Bi crosslinking process occurring upon thermal aging. Finally, the biodisintegration rate of doped Mater‐Bi decreased, thus indicating that EP interfered with the microbial digestion of the polymer films.