Transparent and ultra-tough PVA/alkaline lignin films with UV shielding and antibacterial functions

pH-responsive starch-based bilayer film functionalized with alliin loaded MIL-101 (Fe) for active food packaging

Food packaging films containing antimicrobial reagents play a crucial role in preventing bacterial-induced fruit decay. This study proposes a bilayer film consisting of an internal amino-modified starch hydrophilic layer and an external amino-modified polyvinyl alcohol/polylactic acid hydrophobic layer, embedding alliin@MIL-101(Fe) as an antibacterial agent, utilizing the pH reduction of fruit decay sites to achieve pH-responsive release, enhancing antibacterial performance. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) analyses confirm successful crosslinking between amino and aldehyde groups, resulting in the formation of imine bonds and a mesh-like structure conducive to adsorption. Under acidic conditions, the cumulative release rate of alliin reached 74 % within 36 h. Compared to a simple mixture, the tensile strength of the alliin@MIL/NST-NPVA/PLA film reached 34.771 MPa, and transmittance in the wavelength range of 200-370 nm decreased to 0. The scavenging rate of DPPH free radicals in the film can reach 83 %. In addition, the water vapor permeability and oxygen permeability of the film are approximately 7.62 × 10-16 [g/ (m2‧24 h‧0.1 mm)] and 6.83 (m2‧24 h‧0.1 MPa), respectively; moisture content and water solubility decreased to 10.99 % and 20.77 %. This composite film extended the shelf life of strawberries from 2 to 7 days, significantly enhancing freshness.

Microbial cell factories for bioconversion of lignin to vanillin - Challenges and opportunities: A review

The bioconversion of lignin into vanillin via microbial cell factories offers a promising and sustainable route for producing high-value aromatic compounds from the abundant and underutilized byproducts of plant biomass. This review comprehensively explores the synthesis, structural characteristics, and diverse industrial applications of lignin, while addressing the inherent challenges posed by its complex structure in bioconversion processes. It examines the potential of microbial cell factories for lignin degradation, emphasizing the latest advancements in genetic engineering and metabolic optimization strategies that enhance microbial efficiency in lignin degradation and vanillin biosynthesis. It further assesses the economic feasibility of lignin-to-vanillin conversion by discussing key factors influencing cost-effectiveness and scalability, highlighting the transformative potential for producing high-value aromatic compounds in an environmentally sustainable manner. The review also highlights ongoing research efforts to develop robust microbial strains and optimize metabolic pathways for improved vanillin yield. By integrating multidisciplinary approaches, this review highlights the transformative potential of microbial cell factories to valorize lignin, offering a sustainable pathway for the production of vanillin and related aromatic compounds.

Cellulose and lignin nanoparticles from an Ayurvedic waste stream for essential oil-based active packaging to extend shelf life of strawberries

Cellulose and lignin nanoparticles (NCP and LNP) were successfully extracted from Dashamoola spent material (DSM), a residue from an Ayurvedic decoction. NCP had a particle size of 493.6 nm and a zeta potential of -30.9 mV, indicating good colloidal stability. FTIR confirmed the removal of non-cellulosic components, while TGA demonstrated thermal stability, with major degradation between 260 °C and 350 °C. A semi-crystalline structure of nanocellulose was indicated via XRD analysis. Oil-in-water emulsions of tea tree oil (TTO) were prepared using NCP (C at 4 %), LNP (L at 4 %), and a combination blend (2 % each of C and L in CL_TTO), with 16 % TTO, all in w/v. Among these, CL_TTO emulsions had the smallest particle size and highest stability. PVOH-based films, prepared with a 4 % w/v mixture of CL_TTO emulsion, PVOH, and glycerol, demonstrated improved tensile strength, Young's modulus, water vapour barrier properties, and water repellence. These films blocked 95 % UV transmittance, providing appreciable protection to light-sensitive products. PVOH-CL_TTO films also exhibited strong antioxidant activity (85 % DPPH scavenging) and antimicrobial property against E. coli. These films extended the shelf life of strawberries by preserving lightness, firmness, and pH for 14 days under chilling (4 °C). These findings highlight the potential of NCP and LNP obtained from DSM for producing sustainable active packaging which would valorizing Ayurvedic waste stream.

Lignin reinforced eco-friendly and functional nanoarchitectonics materials with tailored interfacial barrier performance

Exploring innovative and sustainable routes for the production of biodegradable biomass-based materials is critical to promote a circular carbon economy and carbon neutrality goals. Fossil-based non-biodegradable plastic waste poses a nonnegligible threat to humans and the ecological environment, and biomass-based functional materials are becoming increasingly viable alternatives. Lignin, a naturally occurring macromolecular polymer, is green and renewable resource rich in aromatic rings, with biodegradability, biocompatibility, and excellent processability for eco-friendly composites. Moreover, versatile and high tunable lignins can be valorized into functional materials, which are crucial building blocks in the fabrication of biomass-derived composites. Lignin's unique chemical structure, solvent resistance, anti-aging, and anti-ultraviolet functional properties make it highly potential for the fabrication of sustainable biobased barrier materials. This review systematically summarizes the progress in the fabrication and application of lignin-based functional composites, with a particular focus on barrier materials. First, the structural diversity of lignins from different sources and fractionation methods, and the structural modification strategies of lignins are briefly introduced. Then, the multiple barrier performances of lignin-based composites are listed, and the fabrication methods of different composites based on the polymer matrix systems are elaborated. In terms of diverse applications, this review highlights the multifaceted barrier properties of lignin-based composites in oxygen barrier, water vapor barrier, ultraviolet barrier, flame retardant and antibacterial applications. These functional barrier materials are widely used in food/pharmaceutical packaging, agricultural protection, construction, etc., providing an excellent option for sustainable materials with high barrier performance requirements. Finally, the main challenges faced by lignin-based barrier materials and the future directions are proposed.

Utilization of structure-specific lignin extracted from coconut fiber via deep eutectic solvents to enhance the functional properties of PVA nanocomposite films

This study utilized deep eutectic solvents (DES) based on choline chloride/lactic acid (ChCl/LA) to deconstruct coconut fibers. The effects of DES with different temperatures and molar ratios on the yield of lignin, recovery rate of residues, structural changes in lignin and solid residues, and saccharification efficiency were investigated. The results showed that acidic DES treatment effectively deconstructed the coconut fibers, resulting in a high lignin yield of 68.51 % while enhancing the enzymatic saccharification of cellulose, reaching a glucose yield of 85.88 %. The structural characterization of lignin revealed that acidic DES primarily cleaved β-O-4 bonds, yielding coconut fiber lignin with lower molecular weight and higher phenolic hydroxyl groups. Uniform and smooth coconut fiber lignin nanoparticles (CFLNPs) with excellent antioxidant activity were finally obtained by antisolvent method. Furthermore, PVA/CFLNPs nanocomposite films were prepared based on acidic DES CFLNPs. The results of the structural and functional analysis showed that CFLNPs significantly improved the thermal stability, mechanical properties, hydrophobicity, antioxidant and antibacterial activity of the nanocomposite films. In general, this work achieved efficient deconstruction of coconut fibers, providing insights for biorefining in the future, and more importantly, the potential to use the CFLNPs as a choice for active food packaging.

Lignin and green solvent extracted phenolic compounds from date palm leaves as functional ingredients for the formulation of soy protein isolate biocomposite packaging materials: A circular packaging concept

The current study investigated valorization of lignin nanoparticles (LNPs) and phenolic compounds loaded in chitosan (DLECNPs) extracted from date palm leaves into the soy protein isolate (SPI) biocomposite films. The mechanical, structural, barrier, physiochemical, thermal, optical, antioxidant, and antimicrobial properties of the formulated composite films were investigated. The findings showed that the incorporation of DLECNPs into the SPI films significantly improved the film's antioxidant properties by more than 3 times and showed antibacterial inhibition zone in the range of 10-15 mm against six pathogenic bacteria. Further, incorporating LNPs into SPI-DLECNPs films notably improved the mechanical properties from 4.32 MPa and 29.27 % tensile strength and elongation at break, respectively to 10.13 MPa and 54.94 %, the water vapor permeability from 7.38 g/Pa s m to 5.59 g/Pa s m, and the antibacterial inhibition zone from a range of 10.2 mm to 15.0-21.5 mm as well as making the films more heterogeneous and stronger than control SPI film. Moreover, LNPs changed the initial films' color from light yellow to dark red and reduced the films' transparency. The results indicated that LNPs reinforced SPI composite films showed significant improvements in several properties and thus can be used as a potential ingredient for formulation of biodegradable packaging films.

Crosslinking gelatin with robust inherent antibacterial natural polymer for wound healing

Gelatin-based biomaterials are widely acknowledged as a promising choice for wound dressings, given their similarity to the extracellular matrix and biocompatibility. However, the challenge of cross-linking gelatin while preserving its biocompatibility and cost-effectiveness persists. This study aimed to enhance the properties of gelatin by incorporating the oxidized lignosulfonate (OLS) biopolymer as an inexpensive and biocompatible natural material. The polyphenolic structure of OLS acts as both a cross-linking agent and an antibacterial component. The OLS/gelatin films were prepared using a casting method with varying weight ratios (0.1, 0.2, 0.3, 0.4, and 0.5 w/w). FTIR analysis confirmed the formation of Schiff-base and hydrogen bonds between gelatin and OLS. The resulting films exhibited enhanced mechanical properties (Young's modulus ∼40 MPa), no cytotoxicity, and excellent cell adhesion and morphology. Antimicrobial tests showed significant activity against Escherichia coli and Staphylococcus aureus, with higher activity against S. aureus (17 mm inhibition zone and 99 % bactericidal rate). In vivo studies in a mouse model demonstrated that the gelatin/0.2OLS dressing significantly improved wound healing, including re-epithelialization, collagen formation, inflammation reduction, and blood vessel density, compared to untreated wounds. These findings suggest that the synthesized novel gelatin/OLS wound dressing has promising healing and antibacterial properties.

Fabrication of N-halamine/MWPPy-ZnO hybrids based cellulose nanofibril composite films with improved UV-protective, antibacterial, and biofilm control functions

The design and fabrication of synergistic hybrid antibacterial materials is a promising approach for achieving effective sterilization while compensating for the deficiency of a single component. Despite being highly effective biocidal components, the poor UV light stability of some N-halamines limits their applications. This study was conducted to address this issue by the rational integration of cyclic N-halamine precursor (PGHAPA) with microwaved zinc oxide (MWPPy-ZnO) nanoparticles via covalent bonds and the preparation of cellulose nanofibrils based antibacterial composite films after chlorination (CNF/MWPPy-ZnO-PGHAPA-Cl). The proposed films offered tight lamellar structure, considerable thermal stability and better mechanical properties. The results from the FT-IR and XPS experiments provided the evidence of chemical reactions among the PGHAPA, MWPPy-ZnO, and CNF film. Notably, the CNF/MWPPy-ZnO-PGHAPA-Cl films showed improved UV stability with a chlorine content of up to 0.16 % after 24 h of irradiation, which was much greater than that of the CNF/PGHAPA-Cl films. Furthermore, the CNF/MWPPy-ZnO-PGHAPA-Cl films displayed rapid bactericidal activity, inactivating all the contacted Staphylococcus aureus and Escherichia coli O157:H7 strains within 5 min, along with prominent biofilm disruption, indicating great potential for daily food packaging applications.

Mechanistic insights and applications of lignin-based ultraviolet shielding composites: A comprehensive review

Lignin is a green aromatic polymer constructed from repeating phenylpropane units, incorporating features such as phenolic hydroxyl groups, carbonyl groups, and conjugated double bonds that serve as chromophores. These structural attributes enable it to absorb a wide spectrum of ultraviolet radiation within the 250-400 nm range. The resulting properties make lignin a material of considerable interest for its potential applications in polymers, packaging, architectural decoration, and beyond. By examining the structure of lignin, this research delves into the structural influence on its UV-shielding capabilities. Through a comparative analysis of lignin's use in various UV-shielding applications, the study explores the interplay between lignin's structure and its interactions with other materials. This investigation aims to elucidate the UV-shielding mechanism, thereby offering insights that could inform the development of high-value applications for lignin in UV-shielding composite materials.

UV-blocking, antibacterial, corrosion resistance, antioxidant, and fruit packaging ability of lignin-rich alkaline black liquor composite film

The novel multifunctional active packaging composite film with antimicrobial, antioxidant, water-vapor and UV-barrier, and corrosion resistance properties was successfully prepared from waste biomass. In this study, waste poplar sawdust was pretreated using green liquor to extract black liquor (BL). BL was then mixed with polyvinyl alcohol (PVA) solution for synthesizing silver nanoparticles (AgNPs). PVA-BL-AgNPs film was fabricated by solution casting method, and the microstructure characterization and macroscopic performance testing of the composite film were conducted. The results revealed that PVA-BL-AgNPs film exhibited inhibitory effects against Staphylococcus aureus (inhibition zone: 33.6 mm), Pseudomonas aeruginosa (inhibition zone: 31.6 mm), and Escherichia coli (inhibition zone: 32.0 mm). It could eliminate over 99 % of 2,2-diazodi (3-ethyl-benzothiazol-6-sulfonic acid) (ABTS) free radicals and provided 100 % UV-blocking, reducing light-induced food damage. It exhibited the improvement of water-vapor barrier properties and corrosion resistance. In vitro cytotoxicity assays demonstrated that no significant impact occurred on cell proliferation, confirming the safety of the film. Packaging experiments showed that PVA-BL-AgNPs film effectively inhibited milk spoilage and prolonged the shelf-life of bread and bananas. Therefore, PVA-BL-AgNPs film might extend the shelf-life of food and offer significant opportunities in addressing the issues of low safety and environmental pollution associated with traditional packaging films.

Heat-sealable, transparent, and degradable arabinogalactan/polyvinyl alcohol films with UV-shielding, antibacterial, and antioxidant properties

Petroleum-based packaging materials are nondegradable and unsustainable and thus are harmful to the environment. Renewable packaging films prepared from bio-based raw materials are promising alternatives to petroleum-based packaging materials. In this study, colorless and transparent bio-based films were successfully cast using a solution containing a mixture of arabinogalactan (AG) and poly (vinyl alcohol) (PVA). Vanillin was incorporated into the mixture to endow the films with UV-shielding, antioxidant, and antibacterial properties. The morphological, physical, antioxidant, and antibacterial properties of the blend films were then characterized. At an AG:PVA weight ratio of 1:3, and the vanillin content was 0.15 %, the tensile strength of the AG/PVA/Vanillin (APV) films reached ~28 MPa, while their elongation at break reached ~475 %. The addition of vanillin significantly affected the antioxidant and antibacterial properties of the blend films, which exhibited superb UV barrier capacity. The APV films exhibited extremely low oxygen transmittance, delaying the onset of mold/rot in strawberries and reducing their weight loss. Because of the heat sealability of the blend films, they can be used for encapsulating various substances, such as concentrated laundry liquid. Moreover, the blend films were recyclable and biodegradable. Thus, these films have great potential for applications that require sustainable packaging.

Green Extraction of Reed Lignin: The Effect of the Deep Eutectic Solvent Composition on the UV-Shielding and Antioxidant Properties of Lignin

Lignin, the second most abundant natural polymer, is a by-product of the biorefinery and pulp and paper industries. This study was undertaken to evaluate the properties and estimate the prospects of using lignin as a by-product of the pretreatment of common reed straw (Phragmites australis) with deep eutectic solvents (DESs) of various compositions: choline chloride/oxalic acid (ChCl/OA), choline chloride/lactic acid (ChCl/LA), and choline chloride/monoethanol amine (ChCl/EA). The lignin samples, hereinafter referred to as Lig-OA, Lig-LA, and Lig-EA, were obtained as by-products after optimizing the conditions of reed straw pretreatment with DESs in order to improve the efficiency of subsequent enzymatic hydrolysis. The lignin was studied using gel penetration chromatography, UV-vis, ATR-FTIR, and 1H and 13C NMR spectroscopy; its antioxidant activity was assessed, and the UV-shielding properties of lignin/polyvinyl alcohol composite films were estimated. The DES composition had a significant impact on the structure and properties of the extracted lignin. The lignin's ability to scavenge ABTS+• and DPPH• radicals, as well as the efficiency of UV radiation shielding, decreased as follows: Lig-OA > Lig-LA > Lig-EA. The PVA/Lig-OA and PVA/Lig-LA films with a lignin content of 4% of the weight of PVA block UV radiation in the UVA range by 96% and 87%, respectively, and completely block UV radiation in the UVB range.

Preparation and Application of Degradable Lignin/Poly (Vinyl Alcohol) Polymers as Urea Slow-Release Coating Materials

The massive amount of water-soluble urea used leads to nutrient loss and environmental pollution in both water and soil. The aim of this study was to develop a novel lignin-based slow-release envelope material that has essential nitrogen and sulfur elements for plants. After the amination reaction with a hydrolysate of yak hair keratin, the coating formulation was obtained by adding different loadings (2, 5, 8, 14 wt%) of aminated lignin (AL) to 5% polyvinyl alcohol (PVA) solution. These formulations were cast into films and characterized for their structure, thermal stability, and mechanical and physicochemical properties. The results showed that the PVA-AL (8%) formulation had good physical and chemical properties in terms of water absorption and mechanical properties, and it showed good degradation in soil with 51% weight loss after 45 days. It is suitable for use as a coating material for fertilizers. Through high-pressure spraying technology, enveloped urea particles with a PVA-AL (8%) solution were obtained, which showed good morphology and slow-release performance. Compared with urea, the highest urea release was only 96.4% after 30 days, conforming to Higuchi model, Ritger-Peppas model, and second-order dynamic model. The continuous nitrogen supply of PVA-AL coated urea to Brassica napus was verified by potting experiments. Therefore, the lignin-based composite can be used as a coating material to produce a new slow-release nitrogen fertilizer for sustainable crop production.

Effect of DES lignin incorporation on physicochemical, antioxidant and antimicrobial properties of carboxymethyl cellulose-based films

Herein, three pretreated grapevine lignins were incorporated into carboxymethyl cellulose films. The effects of traditional NaOH pretreated lignin and DES (ChCl-LA, ChCl-LA & K2CO3-EG) pretreated lignin on film properties were compared. Modern analytical techniques were employed to systematically characterize the pretreated lignin and the different CMC-lignin films. The results showed that DES lignin was of high purity, low molecular weight, and homogeneous structure. It outperformed traditional NaOH lignin in terms of compatibility with CMC, enabling it to perform its bioactivity and physicochemical functions in films. This feature effectively enhanced the hydrophobicity, UV shielding ability, water vapor barrier, thermal stability, mechanical properties, and biological activity of CMC-DES lignin film. NMR (2D HSQC) showed that the excellent antioxidant and antibacterial capabilities of CMC-DES lignin film are due to the retention of butyl (S) and p-hydroxyphenyl (H) units in DES lignin, resulting in its rich phenolic hydroxyl content. The detailed structural elucidation of DES lignin's chemical interactions with CMC provided valuable insights into the advantageous properties observed in the films, presenting innovative solutions for applications in the food packaging and preservation industries.

Multi-functional polyvinyl alcohol/tannin acid composite films incorporated with lignin nanoparticles loaded by potassium sorbate

The biocompatible, biodegradable and strong polyvinyl alcohol-based films have been widely investigated and used in the field of active packaging. To endow with diverse function, this paper firstly prepared lignin nanoparticles loaded with potassium sorbate (LNP@PS) as additives to exploit additional antibacterial, UV blocking, oxygen barrier, and water barrier properties. Besides, tannin acid (TA) was incorporated for compensating and further enhancing mechanical properties. Results showed that the PVA-based composite films containing 3 % LNP@PS and 5 % TA could achieve the optimal tensile strength at 74.51 MPa, water vapor permeability at 7.015·10-13·g·cm/cm2·s·Pa and oxygen permeability at 1.93 cm3/m2·24 h MPa, which was an 165 % of increase, 47 % and 112 % of reduction respectively compared to pure PVA films. Additionally, the composite films exhibited apparently superior bacteria and oxygen resistance properties evidenced by microbial infection and free radical scavenging performance. In addition, the slow-release effect of PS assisted the strawberry preservation with an extension of 3 days, which provided a promising novel route to prepare active food packaging material.

Starch biocomposites preparation by incorporating organosolv lignins from potato crop residues

Plastic wastes accumulated due to food packaging pose environmental threats. This study proposes biopolymeric films containing lignins extracted from potato crop residues (PCR) through organosolv treatment as a green alternative to non-degradable food packaging. The isolation process yielded 43.9 wt% lignins with a recovery rate of 73.5 wt% achieved under optimum conditions at 180 °C with 50 % v/v ethanol. The extracted lignins were then incorporated into a starch matrix to create biocomposite films. ATR-FTIR analysis confirmed interactions between the starch matrix and extracted lignins, and XRD analysis showed the amorphous structure of lignins, reducing film crystallinity. The addition of 1 wt% of extracted lignins resulted in a 87 % reduction in oxygen permeability, a 25 % increase in the thermal stability of the film, and a 78 % enhancement in antioxidant. Furthermore, introducing 3 wt% lignins led to the lowest water vapor transmission rate, measuring 9.3 × 10-7 kg/s·m2. Morphological studies of the films demonstrated a homogeneous and continuous structure on both the surface and cross-sectional areas when the lignins content was below 7 wt%. These findings highlight the potential of using organosolv lignins derived from potato crop residues as a promising additive for developing eco-friendly films designed for sustainable food packaging.

Bioinspired multiscale cellulose/lignin-silver composite films with robust mechanical, antioxidant and antibacterial properties for ultraviolet shielding

Constructing a high-performance ultraviolet shielding film is an effective way for addressing the growing problem of ultraviolet radiation. However, it is still a great challenge to achieve a combination of multifunctional, excellent mechanical properties and low cost. Here, inspired by the multiscale structure of biomaterials and features of lignin, a multifunctional composite film (CNF/CMF/Lig-Ag) is constructed via a facile vacuum-filtration method by introducing micron-sized cellulose fibers (CMF) and lignin-silver nanoparticles (Lig-Ag NPs) into the cellulose nanofibers (CNF) film network. In this composite film, the microfibers interweave with nanofibers to form a multiscale three-dimensional network, which ensures satisfactory mechanical properties of the composite film. Meanwhile, the Lig-Ag NPs are employed as a multifunctional filler to enhance the composite film's antioxidant, antibacterial and ultraviolet shielding abilities. As a result, the prepared CNF/CMF/Lig-Ag composite film demonstrates excellent mechanical properties (with tensile strength of 133.8 MPa and fracture strain of 7.4 %), good biocompatibility, high thermal stability, potent antioxidant and antibacterial properties. More importantly, such composite film achieves a high ultraviolet shielding rate of 98.2 % for ultraviolet radiation A (UVA) and 99.4 % for ultraviolet radiation B (UVB), respectively. Therefore, the prepared CNF/CMF/Lig-Ag composite film shows great potential in application of ultraviolet protection.

Construction of multiple crosslinked networks for the preparation of high-performance lignin-containing cellulose nanofiber reinforced polyvinyl alcohol films

Polyvinyl alcohol (PVA) film, a promising alternative to non-biodegradable plastic packaging films for food and medical packaging, is limited by poor water resistance. In this work, a simple solvent evaporation self-assembly was used to construct a nanophase separation structure to establish dense interfacial hydrogen bonding, covalent bonding and iron metal ion coordination interactions between lignin-containing cellulose nanofibers (LCNFs) and PVA matrix to improve the interfacial force and solve the problem of poor compatibility of LCNFs in PVA. The iron ion (Fe3+) coordination tended to combine with the more active lignin phenolic hydroxyl group to construct the nanophase separation structure. Covalent crosslinking of glutaraldehyde (GA) improved the interfacial compatibility of PVA/LCNF films, enhanced the interfacial bonding and formed a homogeneous structure. The multi-nanophase structures improved the strength and elastic modulus of the PVA/LCNF film and provided the films with extremely low water absorption, water vapor transmission rate and excellent UV-shielding. Compared with pure PVA film, PVA-10L-5Fe-3GA film had about 106.9 % higher tensile strength, 93.9 % lower water absorption and 93.4 % lower mass loss, 69.8 % lower water vapor transmission coefficient, and was able to shield UV at 200-400 nm, which is highly expected to be used in packaging films.

Antibacterial, antioxidant and fruit packaging ability of biochar-based silver nanoparticles-polyvinyl alcohol-chitosan composite film

Silver nanoparticles were prepared by loading Ag+ into biochar of waste barley distillers' grains shell by reduction with trisodium citrate, and this silver-loaded biochar was introduced into polyvinyl alcohol-chitosan. Various analysis with Fourier Transform Infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis, and water contact angle revealed that biochar-based silver nanoparticle was incorporated into the polyvinyl alcohol-chitosan film, the biochar-based silver nanoparticles-polyvinyl alcohol-chitosan (C-Ag-loaded PVA/CS) composite film had good thermostability and hydrophobicity. Through the analysis via disk diffusion method, the composite containing 3 % of biochar-based silver nanoparticles-polyvinyl alcohol-chitosan had high antibacterial activity (inhibition zone: 18 mm against E. coli and 15 mm against S. aureus), and the bacterial membrane permeability was measured, indicating that C-Ag-loaded PVA/CS composite film could destroy the cell membrane, release intracellular substances, and have high antioxidant activity. During the storage, the weight loss rate of the biochar-based silver nanoparticles-polyvinyl alcohol-chitosan plastic wrap group was 0.14 %, and the titratable acid content only decreased by 0.061 %, which had a good effect on extending the shelf life of blueberries. The C-Ag-loaded PVA/CS composite film could also delay deterioration of blueberries and prolong storage time. Overall, this composite film had potential in food packaging and extending food shelf-life aspects.

Recent advances in plant-based polysaccharide ternary complexes for biodegradable packaging

Polysaccharide-based packaging has been directed toward the development of technologies for the generation of packaging with biodegradable materials that can serve as substitutes for conventional packaging. Polysaccharides are reliable sources of edible packaging materials with excellent renewability, biodegradability, and bio-compatibility as well as antioxidant and antimicrobial activities. Apart from these properties, packaging film developed from a single polysaccharide has various disadvantages due to undesirable properties. Thus, to overcome these problems, researchers focused on ternary blend-based bio-packaging instead of the primary and binary complex to improve their characteristics and properties. The review emphasizes the extraction of polysaccharides and their combination with other polymers to provide desirable characteristics and physico-mechanical properties of the biodegradable film which will upgrade the green packaging technology in the future generation This review also explores the advancement of ternary blend-based biodegradable film and their application in foods with different requirements and the future aspects for developing advanced biodegradable film. Moreover, the review concludes that cellulose, modified starch, and another plant-based polysaccharide film mostly provides good gas barrier property and better tensile strength, which can be used as a safeguard of perishable and semi-perishable foods which brings them closer to replacing commercial synthetic packaging.

Lignin-ultrasound method: Enhancement of antimicrobial capacity of MoS2-containing films

To improve the antimicrobial ability of MoS2-containing films, we used lignin and triple-frequency ultrasound for liquid-phase exfoliation (LPE) to obtain MoS2 nanosheets. Photoresponsive antimicrobial films with MoS2 nanosheets, lignin, polyvinyl alcohol and deep eutectic solvents were subsequently prepared. Lignin functionalized the MoS2 nanosheets by chemically linking with S in MoS2 and significantly improved the exfoliation efficiency. Tri-frequency ultrasound produces beneficial effects on the LPE process by creating a more homogeneous sound field and a stronger degree of cavitation. The concentration of MoS2 nanosheets in the exfoliating solution could reach 1.713 mg/mL under the effect of lignin-ultrasound. The antimicrobial ability of the films was analyzed, and the colony-forming units of E. coli and S. aureus could be reduced from 7 × 106 to 1 × 106 cfu/mL under the irradiation of infrared. The lignin in the film undergoes depolymerization and demethoxylation under the irradiation of infrared to have a more phenolic hydroxyl structure, which confers the growth inhibition ability of the films for bacteria that cannot be in close contact with the film. The method we used has some significance for the preparation of MoS2 nanosheets, and composite films prepared from MoS2, and lignin can be used in food packaging, wound antimicrobials, and other fields.

Efficient ultraviolet blocking film on the lignin-rich lignocellulosic nanofibril from bamboo

The ultraviolet (UV) blocking performance of current bio-based devices is always limited by delignification and exploited chemical treatment. Lignocellulosic nanofibril (LCNF) is a promising green alternative that could efficiently impede UV radiation. Herein, we proposed a robust LCNF film that achieved 99.8 ± 0.19 % UVB blocking, 96.1 ± 0.23 % UVA blocking, and was highly transparent without complex chemical modification. Compared to conventional lignin composites, this LCNF method involves 29.5 ± 2.31 % lignin content directly extracted from bamboo as a broad-spectrum sun blocker. This bamboo-based LCNF film revealed an excellent tensile strength of 94.9 ± 3.6 MPa and outstanding stability, adapting to the natural environment's variability. The residual hemicellulose could also embed the link between lignin and cellulose, confirming high lignin content in the network. The connection between lignin and hemicelluloses in the cellulose network was explored and described for the fibrillation of lignocellulosic nanofibrils. This research highlights the promising development of LCNFs for UV protection and bio-based solar absorption materials.

A facile strategy to fabricate high-barrier, water- and oil-repellent paper with carboxymethyl cellulose/collagen fiber/modified polyvinyl alcohol

Due to the increasingly serious environmental and human health hazards brought by traditional food packaging materials, paper-based packaging materials have become increasingly popular among consumers in recent years. Currently, the fabrication of fluorine-free degradable water- and oil-repellent paper using low-cost bio-based polymers by a simple method is a hot subject in the field of food packaging. In this work, we used carboxymethyl cellulose (CMC), collagen fiber (CF), and modified polyvinyl alcohol (MPVA) to create coatings that were impervious to water and oil. The homogeneous mixture of CMC and CF generated electrostatic adsorption to impart excellent oil repellency to the paper. PVA was chemically modified by sodium tetraborate decahydrate, and the MPVA coating imparted excellent water-repellent properties to the paper. Finally, the water- and oil-proof paper showed excellent water repellency (Cobb value: 1.12 g/m²), oil repellency (kit rating: 12/12), low air permeability (0.3 μm/Pa·s), and stronger mechanical properties (4.19 kN/m). This non-fluorinated degradable water- and oil-repellent paper with high barrier properties prepared by a convenient method is expected to be in widespread use in the food packaging field.

Preparation of an Aminated Lignin/Fe(III)/Polyvinyl Alcohol Film: A Packaging Material with UV Resistance and Slow-Release Function

To reduce the usage of petroleum-based plastic products, a lignin-based film material named aminated lignin/Fe(III)/PVA was developed. The mixture of 8 g lignin, 12 mL diethylenetriamine, 200 mL NaOH solution (0.4 mol·L^-1), and 8 mL formaldehyde was heated at 85 °C for 4 h; after the aminated lignin was impregnated in the Fe(NO₃)₃ solution, a mixture of 3 g aminated lignin/Fe(III), 7 g PVA, and 200 mL NaOH solution (pH 8) was heated at 85 °C for 60 min; after 2 mL of glycerin was added, the mixture was spread on a glass plate to obtain the aminated lignin/Fe(III)/PVA film. This film demonstrated hydrophobicity, an UV-blocking function, and a good slow-release performance. Due to the formation of hydrogen bonds between the hydroxyl groups of lignin and PVA, the tensile strength, the elongation at break, and the fracture resistance of the film were 9.1%, 107.8%, and 21.9% higher than that of pure PVA film, respectively. The iron content of aminated lignin/Fe(III)/PVA was 1.06 wt%, which mainly existed in a trivalent form. The aminated lignin/Fe(III)/PVA film has the potential to be used as a food packaging material with anti-ultraviolet light function and can also be developed as other packaging materials, such as seedling bowls, pots for transplanting, and coating films during transport.

Fabrication of BODIPY/polyvinyl alcohol/alkaline lignin antibacterial composite films for food packing

Foodborne pathogens seriously endanger people's health and cause significant economic losses. Therefore, it is of great significance to design potent packaging materials with the function of alleviating food spoiling and extending shelf life. Here, three BODIPY derivatives (named as N-BDPI, B-BDPI and P-BDPI) were synthesized by substituting the 8-position of BODIPY with naphthalene, biphenyl and pyridine groups, respectively, and their photophysical properties as well as antibacterial capacities were characterized. The results demonstrated that N-BDPI had the best singlet oxygen generation ability and could completely kill S. aureus under light irradiation with the minimum inhibitory concentration of only 50 nmol/L. In addition, 1.0% BDPI@PVA/AL composite film was fabricated by doping N-BDPI into polyvinyl alcohol (PVA) and alkaline lignin (AL) exhibited high antibacterial activity on Gram-positive bacteria. The coating of strawberries with 1.0% BDPI@PVA/AL film not only effectively inhibited the mildew of strawberries, but also extended their shelf life.