Locust bean milling-derived dust as a raw material for the development of biodegradable bioplastics with antioxidant activity.

BACKGROUND: Non-value agrifood byproducts are rich in biomolecules such as proteins and polysaccharides, and possess film-forming ability, motivating their use in the development of biodegradable plastics. This work studied the feasibility of using locust bean milling-derived dust (LBMD) as a source of biomolecules suitable for developing biodegradable plastics. RESULTS: LBMD is composed of 56% protein, 28% carbohydrate, 10% moisture, 6% lipid, and 2% ash. In addition, phenolic compounds are also present. The carbohydrates are mainly composed by (1 → 4)-mannose, (1 → 4,6)-mannose, and t-galactose glycosidic linkages. Depending on the LBMD concentration used, when employed in casting biodegradable plastics, LBMD yields transparent yellowish bioplastics with 90% elongation at break and surface water contact angles ranging from 60° to 90°. Additionally, LBMD-based bioplastics display antioxidant activity, inhibiting cationic 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals up to 61% in just 24 h. LBMD-based bioplastics are disintegrated when incubated on the soil surface for 34 weeks, perhaps acting as a soil nutrient. CONCLUSION: LBMD represents a potential source of biomolecules for producing transparent, flexible, water tolerant, antioxidant, and biodegradable bioplastics, opening up opportunities to implement a novel circular strategy to valorize this locust bean industry byproduct. © 2022 Society of Chemical Industry.

The Role of Porphyrinoid Photosensitizers for Skin Wound Healing.

Microorganisms, usually bacteria and fungi, grow and spread in skin wounds, causing infections. These infections trigger the immune system and cause inflammation and tissue damage within the skin or wound, slowing down the healing process. The use of photodynamic therapy (PDT) to eradicate microorganisms has been regarded as a promising alternative to anti-infective therapies, such as those based on antibiotics, and more recently, is being considered for skin wound-healing, namely for infected wounds. Among the several molecules exploited as photosensitizers (PS), porphyrinoids exhibit suitable features for achieving those goals efficiently. The capability that these macrocycles display to generate reactive oxygen species (ROS) gives a significant contribution to the regenerative process. ROS are responsible for avoiding the development of infections by inactivating microorganisms such as bacteria but also by promoting cell proliferation through the activation of stem cells which regulates inflammatory factors and collagen remodeling. The PS can act solo or combined with several materials, such as polymers, hydrogels, nanotubes, or metal-organic frameworks (MOF), keeping both the microbial photoinactivation and healing/regenerative processes' effectiveness. This review highlights the developments on the combination of PDT approach and skin wound healing using natural and synthetic porphyrinoids, such as porphyrins, chlorins and phthalocyanines, as PS, as well as the prodrug 5-aminolevulinic acid (5-ALA), the natural precursor of protoporphyrin-IX (PP-IX).

Effect of Continuous and Discontinuous Microwave-Assisted Heating on Starch-Derived Dietary Fiber Production.

Dietary fiber can be obtained by dextrinization, which occurs while heating starch in the presence of acids. During dextrinization, depolymerization, transglycosylation, and repolymerization occur, leading to structural changes responsible for increasing resistance to starch enzymatic digestion. The conventional dextrinization time can be decreased by using microwave-assisted heating. The main objective of this study was to obtain dietary fiber from acidified potato starch using continuous and discontinuous microwave-assisted heating and to investigate the structure and physicochemical properties of the resulting dextrins. Dextrins were characterized by water solubility, dextrose equivalent, and color parameters (L* a* b*). Total dietary fiber content was measured according to the AOAC 2009.01 method. Structural and morphological changes were determined by means of SEM, XRD, DSC, and GC-MS analyses. Microwave-assisted dextrinization of potato starch led to light yellow to brownish products with increased solubility in water and diminished crystallinity and gelatinization enthalpy. Dextrinization products contained glycosidic linkages and branched residues not present in native starch, indicative of its conversion into dietary fiber. Thus, microwave-assisted heating can induce structural changes in potato starch, originating products with a high level of dietary fiber content.

An Insight into the Role of Non-Porphyrinoid Photosensitizers for Skin Wound Healing.

The concept behind photodynamic therapy (PDT) is being successfully applied in different biomedical contexts such as cancer diseases, inactivation of microorganisms and, more recently, to improve wound healing and tissue regeneration. The effectiveness of PDT in skin treatments is associated with the role of reactive oxygen species (ROS) produced by a photosensitizer (PS), which acts as a "double agent". The release of ROS must be high enough to prevent microbial growth and, simultaneously, to accelerate the immune system response by recruiting important regenerative agents to the wound site. The growing interest in this subject is reflected by the increasing number of studies concerning the optimization of relevant experimental parameters for wound healing via PDT, namely, light features, the structure and concentration of the PS, and the wound type and location. Considering the importance of developing PSs with suitable features for this emergent topic concerning skin wound healing, in this review, a special focus on the achievements attained for each PS class, namely, of the non-porphyrinoid type, is given.

Enzymatic synthesis of poly(catechin)-antibiotic conjugates: an antimicrobial approach for indwelling catheters.

Biofilm formation in urinary indwelling catheters is one of the most critical issues that patients face. Catheters were coated with poly(catechin)-antibiotic conjugates with enhanced antimicrobial properties. Catechin was conjugated with two antibiotics, namely trimethoprim (TMP) and sulfamethoxazole (SMZ) via activation with N,N'-disuccinimidyl carbonate (DSC) and subsequent coupling to molecules containing α-amine moieties. Silicone and polyurethane catheters were functionalized in situ through laccase oxidation of catechin-antibiotic conjugates. Four antimicrobial coatings were produced, namely with poly(catechin), poly(catechin)-TMP, poly(catechin)-SMZ and poly(catechin)-TMP-SMZ. The bacterial adhesion reduction was tested on the functionalized devices using gram-negative and gram-positive strains. The most significant reduction in adhesion was observed with poly(catechin)-TMP (gram-negative -85 % and gram-positive -87 %) and with poly(catechin)-TMP-SMZ (gram-negative -85 % and gram-positive -91 %). The cytotoxicity to mammalian cells was tested by indirect contact for 5 days and revealed that all the tested coatings supported more than 90 % of viable cells. A promising approach for the increase of the indwelling catheter lifespan was developed aiming to reduce catheter-associated chronic infections.

Antimicrobial lubricant formulations containing poly(hydroxybenzene)-trimethoprim conjugates synthesized by tyrosinase.

Poly(hydroxybenzene)-trimethoprim conjugates were prepared using methylparaben as substrate of the oxidative enzyme tyrosinase. MALDI-TOF MS analysis showed that the enzymatic oxidation of methylparaben alone leads to the poly(hydroxybenzene) formation. In the presence of trimethoprim, the methylparaben tyrosinase oxidation leads poly(hydroxybenzene)-trimethoprim conjugates. All of these compounds were incorporated into lubricant hydroxyethyl cellulose/glycerol mixtures. Poly(hydroxybenzene)-trimethoprim conjugates were the most effective phenolic structures against the bacterial growth reducing by 96 and 97% of Escherichia coli and Staphylococcus epidermidis suspensions, respectively (after 24 h). A novel enzymatic strategy to produce antimicrobial poly(hydroxybenzene)-antibiotic conjugates is proposed here for a wide range of applications on the biomedical field.

Exploring novel organocatalytic-acetylated pea starch blends in the development of hot-pressed bioplastics.

Acetylated starch shows enhanced thermal stability and moisture resistance, but its compatibilization with other more hydrophilic polysaccharides remains poor or unknown. In this study, the feasibility of thermomechanically compounding organocatalytically acetylated pea starch (APS), produced at two different degrees of substitution with alkanoyl groups (DSacyl, 0.39 and 1.00), with native pea starch (NPS), high (HMP) and low methoxyl (LMP) citrus pectin, and sugar beet pectin (SBP, a naturally acetylated pectin) for developing hot-pressed bioplastics was studied. Generally, APS decreased hydrogen bonding (ATR-FTIR) and crystallinity (XRD) of NPS films at different levels, depending on its DSacyl. The poor compatibility between APS and NPS or HMP was confirmed by ATR-FTIR imaging. Contrariwise, APS with DSacyl 1 was effectively thermomechanically mixed with the acetylated SBP matrix, maintaining homogeneous distribution within it (ATR-FTIR imaging). APS (any DSacyl) significantly increased the visible/UV light opacity of NPS-based films and decreased their water vapor transmission rate (WVTR, by ca. 11 %) and surface water wettability (by ca. 3 times). In comparison to NPS-APS films, pectin-APS showed higher visible/UV light absorption, tensile strength (ca.2.9-4.4 vs ca.2.4 MPa), and Young's modulus (ca.96-116 vs ca.60-70 MPa), with SBP-APS presenting significantly lower water wettability than the rest of the films.

Controlling Morphing Behavior in 4D Printing: A Review About Microstructure and Macrostructure Changes in Polylactic Acid.

Four-dimensional (4D) printing combines stimulus-responsive materials with additive manufacturing (AM) technologies. This new concept of printing three-dimensional (3D) objects opens the possibility for solving processing issues, through the production of complex geometries that can undergo programmed temporal changes in response to external stimuli. However, as 4D technology emerges from AM, various challenges still need to be explored, such as the controlled morphing effect. Understanding the aspects related to this behavior, both at the macroscopic level of the structure and at the microscopic level of the polymeric chain, is fundamental. Focused on thermoplastic poly(lactic acid) (PLA) printed by fused deposition modeling, this review addressed the influence of molecular weight, polymeric chain modifications, and 3D printing parameters on the shape change effect of a PLA-based material. The glass transition temperature proved to be a highly important parameter, which can be modified by molecular weight changes. Nozzle temperature, fill density, print patterns, and raster angle are 3D printing parameters that influence the material shape change. Shape recovery is highly dependent on the recovery temperature. Potential applications for shape memory structures are also addressed in this review.

Starch consolidation of calcium carbonate as a tool to develop lightweight fillers for LDPE-based plastics.

Calcium carbonate (CaCO3) is used as a filler to improve the stiffness and processability of plastics at low cost. However, its high density limits the quantity to be used. In this work, the feasibility of using starch consolidation of eggshells-derived CaCO3 (ES) to develop lightweight fillers for low density polyethylene (LDPE)-based materials was studied. Starch, recovered from potato by-products, was combined with ES, gelatinized, dried, and milled as a fine powder. The obtained ES/starch-based particles were then compounded with LDPE and their influence on chromatic, mechanical, morphological, and density properties of mold injected LDPE-based materials was studied. Commercially available CaCO3 (COM) was used as control. ES/starch particles were 18 times less dense than the commercially available CaCO3 (2.62 g cm-3). When incorporated into LDPE-based formulations, ES/starch originated brownish materials with lower density (1.18 g cm-3) and higher stiffness (542 MPa of Young's modulus) than those produced with the COM sample (1.33 g cm-3 of density; 221 MPa of Young's modulus). Therefore, starch consolidation of ES revealed to be a promising approach to develop lightweight fillers able to provide stiffness and color to LDPE-based plastics, while valorizing biomolecules-rich by-products.

Potato Chips Byproducts as Feedstocks for Developing Active Starch-Based Films with Potential for Cheese Packaging.

The potato chip industry generates brownish frying residues, which are usually landfilled. While spent frying oil has value as biodiesel, the defatted brownish water-soluble extract (BrE) does not yet have an application. In this work, it was hypothesized that BrE can be a source of compounds for active packaging. BrE is composed of carbohydrates (66.9%), protein (5.7%), and a small amount of phenolics and esterified fatty acids. When incorporated into starch-based formulations and casted, BrE at 5%, 10%, and 15% w/w (dry starch weight) conferred a yellowish coloration while maintaining the transparency of neat films. The BrE increased the films' traction resistance, elasticity, and antioxidant activity while decreasing their hydrophilicity. Furthermore, starch/15% BrE-based films showed diminished water vapor and good UV-light barrier properties. Their contact with sliced cheese did not change the products' hardness during storage (14 days). Weight loss of the cheese was observed after 7 days of storage, stabilizing at 6.52%, contrary to the cheese packed in polyamide (PA)/polyethylene (PE), already used in food packaging. The cheese packed in the starch/15% BrE-based films showed a significant yellowish darkening and lower content of volatile oxidation products compared to the PA/PE. Therefore, BrE revealed to have compounds with the potential to tune the performance of starch-based films for food packaging.

Starch-based films doped with porphyrinoid photosensitizers for active skin wound healing.

Starch is a biodegradable and biocompatible carbohydrate that, when combined with bioactive molecules, can be processed as biomimetic platforms with enhanced performance, allowing its use as active wound dressing materials. Porphyrinoid photosensitizers can tune the physicochemical/functional profile of biomacromolecules, allowing their use in anti-infective strategies. In this work, the feasibility of using the cationic 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetraiodide (TMPyP) to enhance the physicochemical, mechanical, antimicrobial performance, and wound healing ability of casted starch-based films was studied. TMPyP conferred a reddish coloration to the films, maintaining their pristine transparency. It increased by 87 % the films hydrophobicity and, depending on the TMPyP used, conferred mobility to the starch polymeric chains. Starch/TMPyP-based films effectively photoinactivated Escherichia coli (>99.99 %) and favored the wound healing process, even in the absence of light. Therefore, the incorporation of TMPyP into starch-based formulations revealed to be a promising strategy to tune the films compaction degree while giving rise to water tolerant and photosensitive biomaterials that can act as multitarget antimicrobial medical dressings and glycocarriers of active compounds relevant for effective skin wound healing.

Influence of UV degradation of bioplastics on the amplification of mercury bioavailability in aquatic environments.

Bioplastics have emerged to minimize the ecological footprint of non-degradable plastics. However, the effect of their degradation in aquatic systems, including the interaction with toxic metals, is still unexplored. In this work, the influence of UV-aging on structure, chemistry, wettability, rigidity, and Hg-sorption of commercially available bioplastic (BIO)- and polyethylene (PE)-based films was studied. To mimetize the materials disposal in fresh-/saltwaters, non-saline/saline aqueous solutions were used in Hg-sorption studies. ATR-FTIR spectra revealed that the BIO film was a coblended starch/polyester-based material, whose microstructure, physicochemical, and mechanical properties changed after UV-aging to a higher extent than in PE film. AFM and kinetic modelling pointed out electrostatic interactions/complexation as the mechanisms involved in the increased Hg-sorption by the UV-aged BIO film. An increased salinity did not impair its Hg-sorption. Therefore, when disposed in aquatic systems, starch/polyester-based bioplastics can play a potential vector for amplifying Hg along the food chain.

Coffee By-Products and Their Suitability for Developing Active Food Packaging Materials.

The coffee industry generates a wide variety of by-products derived from green coffee processing (pulp, mucilage, parchment, and husk) and roasting (silverskin and spent coffee grounds). All these fractions are simply discarded, despite their high potential value. Given their polysaccharide-rich composition, along with a significant number of other active biomolecules, coffee by-products are being considered for use in the production of plastics, in line with the notion of the circular economy. This review highlights the chemical composition of coffee by-products and their fractionation, evaluating their potential for use either as polymeric matrices or additives for developing plastic materials. Coffee by-product-derived molecules can confer antioxidant and antimicrobial activities upon plastic materials, as well as surface hydrophobicity, gas impermeability, and increased mechanical resistance, suitable for the development of active food packaging. Overall, this review aims to identify sustainable and eco-friendly strategies for valorizing coffee by-products while offering suitable raw materials for biodegradable plastic formulations, emphasizing their application in the food packaging sector.

Hydrophobic Starch-Based Films Using Potato Washing Slurries and Spent Frying Oil.

Starch is a promising candidate for preparing biodegradable films with useful gas barriers and thermoplastic capabilities. However, these materials are hydrophilic and brittle, thus limiting their application range. To overcome these drawbacks, it has been hypothesized that starch can be hydrophobized and plasticized during the starch-based film production using a single-step approach and following transesterification principles. In this work, KOH powder and spent frying oil (SFO) were used as an alkaline catalyst and a source for triacylglycerides, respectively, to promote the modification of starch. Different ratios of SFO (w/w related to the dried starch weight) were tested. When compared to the neat films (without a catalyst and SFO), the incorporation of at least 15% SFO/KOH gave rise to transparent, hydrophobic (water contact angles of ca. 90∘), stretchable (ca. 20×), elastic (ca. 5×), and water tolerant starch-based films, contrary to the films produced without the catalyst. ATR-FTIR and 1H NMR revealed structural differences among the produced films, suggesting that starch was modified with the SFO-derived fatty acids. Therefore, adding KOH during the potato starch/spent frying oil-based film's production was determined to be a promising in situ strategy to develop starch-based materials with improved hydrophobicity and flexibility, while valorizing the potato chip industry's byproducts.

Relevance of genipin networking on rheological, physical, and mechanical properties of starch-based formulations.

The small amount of proteins in starch-rich food industry byproducts can be an advantage to crosslink with genipin and tailor the performance of biobased films. In this work, genipin was combined with non- purified starch recovered from industrial potato washing slurries and used for films production. Starch recovered from potato washing slurries contained 0.75% protein, 2 times higher than starch directly obtained from potato and 6 times higher than the commercial one. Starch protein-genipin networks were formed with 0.05% and 0.10% genipin, gelatinized at 75 °C and 95 °C in presence of 30% glycerol. Bluish colored films were obtained in all conditions, with the higher surface roughness (Ra, 1.22 µm), stretchability (elongation, 31%), and hydrophobicity (water contact angle, 127°) for 0.10% genipin and starch gelatinized at 75 °C. Therefore, starch-rich byproducts, when combined with genipin, are promising for surpassing the starch-based films hydrophilicity and mechanical fragilities while providing light barrier properties.

Coffee silverskin and starch-rich potato washing slurries as raw materials for elastic, antioxidant, and UV-protective biobased films.

Food processing wastes together with the perishable foodstuff loss promote environmental and societal concerns. Food byproducts can have value as a source of functional molecules for developing active packaging without food waste, under a circular economy. Nevertheless, the often-associated extraction/chemical processes compromise the sustainability of food byproducts reusability. In this work, coffee silverskin (CS) and starch, recovered from coffee roasting and potato industries, respectively, were together gelatinized to form in-situ films. Targeting to fit with the food application requirements, it is important to understand the influence of crude CS amount (1%, 5%, and 10% w/w of dry starch weight) on potato starch-based film properties. CS conferred a brownish coloration to the films, maintaining their transparency. The films colour intensity, antioxidant activity, and water tolerance were directly related with the CS dosage. Moreover, as high the CS amount, higher the elasticity, stretchability, and UV radiation absorption of the pristine films. These data emphasized that CS molecules extracted during gelatinization prevented the starch-starch hydrogen bonding and conferred functional and barrier properties. Overall, adding crude CS during potato starch gelatinization revealed to be an efficient strategy to tune the performance of potato starch-based films, opening an opportunity for valorising coffee roasting and potato byproducts.

Feasibility of chitosan crosslinked with genipin as biocoating for cellulose-based materials.

Crosslinking with genipin increases the acidic stability of chitosan-based materials, opening an opportunity to explore new applications. In this work, the viability of using chitosan-genipin solutions on cellulose-based materials coating was studied. Non-calendered paper and cardboard were used as raw materials. Different number of chitosan-genipin coating layers (1, 3, 6, 20, and 30) were applied and their influence on the materials mechanical, physicochemical, and barrier properties was studied. The small thickness and basis weight of non-calendered paper resulted in an inefficient adhesion of chitosan-genipin coating to the cellulose fibers. However, in cardboard, chitosan-genipin created a dense layer onto the cellulosic-fibers surface without impairing their mechanical properties. It conferred a greenish color, whose intensity increased with the layers number. The chitosan-genipin coating decreased the cardboard air and water vapor permeability up to 71 % and 52 %, respectively, and acted as a physical barrier for cardboard compounds leaching, being suitable for covering cellulose-based materials.

Graphene Derivatives in Biopolymer-Based Composites for Food Packaging Applications.

This review aims to showcase the current use of graphene derivatives, graphene-based nanomaterials in particular, in biopolymer-based composites for food packaging applications. A brief introduction regarding the valuable attributes of available and emergent bioplastic materials is made so that their contributions to the packaging field can be understood. Furthermore, their drawbacks are also disclosed to highlight the benefits that graphene derivatives can bring to bio-based formulations, from physicochemical to mechanical, barrier, and functional properties as antioxidant activity or electrical conductivity. The reported improvements in biopolymer-based composites carried out by graphene derivatives in the last three years are discussed, pointing to their potential for innovative food packaging applications such as electrically conductive food packaging.

Tailoring the surface properties and flexibility of starch-based films using oil and waxes recovered from potato chips byproducts.

Agrofood byproducts may be exploited as a source of biomolecules suitable for developing bioplastic materials. In this work, the feasibility of using starch, oil, and waxes recovered from potato chips byproducts for films production was studied. The recovered potato starch-rich fraction (RPS) contained an amylopectin/amylose ratio of 2.3, gelatinization temperatures varying from 59 to 71 °C, and a gelatinization enthalpy of 12.5 J/g, similarly to a commercial potato starch (CPS). Despite of its spherical and oval granules identical to CPS, RPS had a more amorphous structure and gave rise to low viscous suspensions, contradicting the typical B-type polymorph crystal structure and sluggish dispersions of CPS, respectively. When used for films production, RPS originated transparent films with lower roughness and wettability than CPS-based films, but with higher stretchability. In turn, when combined with RPS and CPS, oil or waxes recovered from frying residues and potato peels, respectively, allowed to develop transparent yellowish RPS- and CPS-based films with increased surface hydrophobicity, mechanical traction resistance, elasticity, and/or plasticity. Therefore, potato chips industry byproducts revealed to have thermoplastic and hydrophobic biomolecules that can be used to efficiently develop biobased plastics with improved surface properties and flexibility, opening an opportunity for their valorization.

CotA laccase-ABTS/hydrogen peroxide system: An efficient approach to produce active and decolorized chitosan-genipin films.

Chitosan-genipin films present a bluish-green color due to the conjugated double bonds formed when monomeric or dimeric genipin residues bridge chitosan. This phenomenon limits their use when colorless materials are required. In this work, a two-step oxidation strategy was developed aiming to remove color from chitosan-genipin films while preserving their functional properties. A combined system using the recombinant CotA laccase from Bacillus subtilis mediated by 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) followed by a H2O2 oxidation step was settled. ABTS boosted the laccase performance resulting in light brown chitosan-genipin films that were further decolorized upon immersion in a 5% H2O2 solution at pH 11.0 and 40°C for 30min. The applied methodology leads to films that sustain both acidic stability and antioxidant capacity of the pristine films. Overall, the combined CotA laccase-ABTS/hydrogen peroxide developed methodology efficiently produce active and decolorized chitosan-genipin films with potential for application as eco-friendly transparent material which may have application as food packaging.