Commercial Marine-Degradable Polymers for Flexible Packaging

Production of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from CO2 via pH-Stat Jar Cultivation of an Engineered Hydrogen-Oxidizing Bacterium Cupriavidus necator

The copolyester of 3-hydroxybutyrate (3HB) and 3-hydoxyhexanoate (3HHx), PHBHHx, is a biodegradable plastic characterized by high flexibility, softness, a wide process window, and marine biodegradability. PHBHHx is usually produced from structurally related carbon sources, such as vegetable oils or fatty acids, but not from inexpensive carbon sources such as sugars. In previous studies, we demonstrated that engineered strains of a hydrogen-oxidizing bacterium, Cupriavidus necator, synthesized PHBHHx with a high cellular content not only from sugars but also from CO2 as the sole carbon source in the flask culture. In this study, the highly efficient production of PHBHHx from CO2 was investigated via pH-stat jar cultivation of recombinant C. necator strains while feeding the substrate gas mixture (H2/O2/CO2 = 80:10:10 v/v%) to a complete mineral medium in a recycled-gas, closed-circuit culture system. As a result, the dry cell mass and PHBHHx concentration with the strain MF01/pBPP-ccrMeJAc-emd reached up to 59.62 ± 3.18 g·L-1 and 49.31 ± 3.14 g·L-1, respectively, after 216 h of jar cultivation with limited addition of ammonia and phosphate solutions. The 3HHx composition was close to 10 mol%, which is suitable for practical applications. It is expected that the autotrophic cultivation of the recombinant C. necator can be feasible for the mass production of PHBHHx from CO2.

Biodegradation of Plastics Induced by Marine Organisms: Future Perspectives for Bioremediation Approaches

Plastic pollution is a distinctive element of the globalized world. In fact, since the 1970s the expansion and use of plastics, particularly in the consumer and commercial sectors, has given this material a permanent place in our lives. The increasing use of plastic products and the wrong management of end-of-life plastic products have contributed to increasing environmental pollution, with negative impacts on our ecosystems and the ecological functions of natural habitats. Nowadays, plastic pollution is pervasive in all environmental compartments. As aquatic environments are the dumping points for poorly managed plastics, biofouling and biodegradation have been proposed as promising approaches for plastic bioremediation. Known for the high stability of plastics in the marine environment, this represents a very important issue to preserve marine biodiversity. In this review, we have summarized the main cases reported in the literature on the degradation of plastics by bacteria, fungi, and microalgae and the degradation mechanisms involved, to highlight the potential of bioremediation approaches to reduce macro and microplastic pollution.

Physical, Mechanical, and Structural Properties of the Polylactide and Polybutylene Adipate Terephthalate (PBAT)-Based Biodegradable Polymer during Compost Storage

Today, packaging is an integral part of any food product, preserving its quality and safety. The use of biodegradable packaging as an alternative to conventional polymers reduces the consumption of synthetic polymers and their negative impacts on the environment. The purpose of this study was to analyze the properties of a biodegradable compound based on polylactide (PLA) and polybutylene adipate terephthalate (PBAT). Test samples were made by blown extrusion. The structural, physical, and mechanical properties of the PLA/PBAT material were studied. The property variations during compost storage in the lab were monitored for 365 days. The physical and mechanical properties were measured in accordance with the GOST 14236-2017 (ISO 527-2:2012) standard. We measured the tensile strength and elongation at rupture. We used attenuated total reflectance Fourier transform infrared microscopy (ATR-FTIR) to analyze the changes in the material structure. This paper presents a comparative analysis of the strengths of a biodegradable material and grade H polyethylene film (manufactured to GOST 10354-82). PLA/PBAT's longitudinal and transverse tensile strengths are 14.08% and 32.59% lower than those of LDPE, respectively. Nevertheless, the results indicate that, given its physical and mechanical properties, the PLA/PBAT material can be an alternative to conventional PE film food packaging. The structural study results are in good agreement with the physical and mechanical tests. Micrographs clearly show the surface deformations of the biodegradable material. They increase with the compost storage duration. The scanning microscopy (SEM) surface analysis of the original PLA/PBAT films indicated that the PLA structure is similar to that of a multilayer shell or sponge, which is visible at medium and especially high magnification. We conclude that PLA/PBAT-based biodegradable materials are potential substitutes for conventional PE polymer films.

Facemask: Protection or threat?

Facemasks were widely used as a protection against SARS-COV-2, which significantly reduced COVID-19 transmission during the pandemic. However, concerns have been raised regarding its adverse impacts on human health due to intense use and mismanagement. Although rampant plastic littering was the norm before the pandemic, the magnitude of the problem is worsening as potentially COVID-19-infected facemasks are thrown along the shoreline. This study assessed the discarded facemasks on the most popular beach destinations in Mati City, Davao Oriental, Philippines. A total of N = 284 discarded facemasks were found in a cumulative area of 22,500 m², with an average density of 8.4 × 10^-4 items/m². The surgical facemask (82 %; n = 234) was the most abundant type of facemask found in the areas, followed by KF94 (16 %; n = 45) and KN95 (2 %; n = 5). The Analysis of Variance (ANOVA) showed significant differences in the visual counts of facemasks on the three beaches (p < 0.05).

Novel Production Methods of Polyhydroxyalkanoates and Their Innovative Uses in Biomedicine and Industry

Polyhydroxyalkanoate (PHA), a biodegradable polymer obtained from microorganisms and plants, have been widely used in biomedical applications and devices, such as sutures, cardiac valves, bone scaffold, and drug delivery of compounds with pharmaceutical interests, as well as in food packaging. This review focuses on the use of polyhydroxyalkanoates beyond the most common uses, aiming to inform about the potential uses of the biopolymer as a biosensor, cosmetics, drug delivery, flame retardancy, and electrospinning, among other interesting uses. The novel applications are based on the production and composition of the polymer, which can be modified by genetic engineering, a semi-synthetic approach, by changing feeding carbon sources and/or supplement addition, among others. The future of PHA is promising, and despite its production costs being higher than petroleum-based plastics, tools given by synthetic biology, bioinformatics, and machine learning, among others, have allowed for great production yields, monomer and polymer functionalization, stability, and versatility, a key feature to increase the uses of this interesting family of polymers.

The effects of polypropylene microplastics on the DBP formation under the chlorination and chloramination processes

With the increased use of microplastics in modern society, tonnes of various microplastics (MPs) end up in natural and engineered water systems if not properly handled. Being a class of organics, the role of MPs during the disinfection of water treatment systems is still unclear at this stage. In the current experimental study, the formation of 6 typical disinfection by-products (DBPs) was investigated using varying concentrations of polypropylene (PP) MPs under various aquatic chemistry conditions and disinfectants. All investigated DBPs were detected, during the chlorination of PP, with an average CHCl₃ concentration of 378 μg/g, and other DBPs, including CHCl₂Br, TCA, DCAN, 1,1-DCP, and TCNM, were present in less than 60 μg/g, on average. When PP coexisted with Suwannee River Fulvic acid (SRFA), a suppression of DBP formation was observed with a 56% net reduction compared with a condition of PP alone. The dynamic balance of being a DBP precursor, or a scavenger, by absorbing the organics of PP is subjected to aquatic chemistry. Increasing the pH decreases the HOCl concentrations, reducing the PP oxidation capacity and DBP formation. As salinity increases, the aggregation of PP can reduce the reaction sites on the surface of PP and enhance the adsorption of SRFA, hence lowering the formation of DBPs.

In silico identification of bacterial seaweed-degrading bioplastic producers

There is an urgent need to replace petroleum-based plastic with bio-based and biodegradable alternatives. Polyhydroxyalkanoates (PHAs) are attractive prospective replacements that exhibit desirable mechanical properties and are recyclable and biodegradable in terrestrial and marine environments. However, the production costs today still limit the economic sustainability of the PHA industry. Seaweed cultivation represents an opportunity for carbon capture, while also supplying a sustainable photosynthetic feedstock for PHA production. We mined existing gene and protein databases to identify bacteria able to grow and produce PHAs using seaweed-derived carbohydrates as substrates. There were no significant relationships between the genes involved in the deconstruction of algae polysaccharides and PHA production, with poor to negative correlations and diffused clustering suggesting evolutionary compartmentalism. We identified 2 987 bacterial candidates spanning 40 taxonomic families predominantly within Alphaproteobacteria, Gammaproteobacteria and Burkholderiales with enriched seaweed-degrading capacity that also harbour PHA synthesis potential. These included highly promising candidates with specialist and generalist specificities, including Alteromonas, Aquisphaera, Azotobacter, Bacillus, Caulobacter, Cellvibrionaceae, Duganella, Janthinobacterium, Massilia, Oxalobacteraceae, Parvularcula, Pirellulaceae, Pseudomonas, Rhizobacter, Rhodanobacter, Simiduia, Sphingobium, Sphingomonadaceae, Sphingomonas, Stieleria, Vibrio and Xanthomonas. In this enriched subset, the family-level densities of genes targeting green macroalgae polysaccharides were considerably higher (n=231.6±68.5) than enzymes targeting brown (n=65.34±13.12) and red (n=30.5±10.72) polysaccharides. Within these organisms, an abundance of FabG genes was observed, suggesting that the fatty acid de novo synthesis pathway supplies (R)-3-hydroxyacyl-CoA or 3-hydroxybutyryl-CoA from core metabolic processes and is the predominant mechanism of PHA production in these organisms. Our results facilitate extending seaweed biomass valorization in the context of consolidated biorefining for the production of bioplastics.

Sustainable Wax Coatings Made from Pine Needle Extraction Waste for Nanopaper Hydrophobization

We combine renewable and waste materials to produce hydrophobic membranes in the present work. Cellulose nanopaper prepared from paper waste was used as a structural component for the membrane. The pine wax was reclaimed from pine needle extraction waste and can be regarded as a byproduct. The dip-coating and spray-coating methods were comprehensively compared. In addition, the solubility of wax in different solvents is reported, and the concentration impact on coating quality is presented as the change in the contact angle value. The sensile drop method was used for wetting measurements. Spray-coating yielded the highest contact angle with an average of 114°, while dip-coating reached an average value of 107°. Scanning electron microscopy (SEM) was used for an in-depth comparison of surface morphology. It was observed that coating methods yield significantly different microstructures on the surface of cellulose fibers. The wax is characterized by nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC). Pine wax has a melting temperature of around 80 °C and excellent thermal stability in oxygen, with a degradation peak above 290 °C. Fourier transform infrared spectroscopy (FTIR) was used to identify characteristic groups of components and show the changes on coated nanopaper. Overall, the results of this work yield important insight into wax-coated cellulose nanopapers and a comparison of spray- and dip-coating methods. The prepared materials have a potential application as membranes and packaging materials.

Bio-Based Plastics Production, Impact and End of Life: A Literature Review and Content Analysis

The accumulation of plastic wastes is one of the most widely spread problems affecting the environment. The reality that plastics can be made from renewable resources and degrade naturally has prompted academics to think outside the box to develop “better for the environment” items. In this paper, a bibliometric analysis of the scholarly publications related to bio-based plastics within the last 20 years is presented. Annual progression, geographic and research area distribution, and keyword co-occurrence were all examined. Six distinct clusters emerged from keyword analysis, which were further categorized into three directions: production to marketing; impact on the environment, economy, and society; and end-of-life (EoL) options. The major focus was on how to counter the weaknesses and challenges of bio-based plastics and take opportunities using the inherent advantages of bio-based plastics. Comprehensive studies regarding the impact of bio-based plastics on the environment, economy and social sustainability are still deficient. Although there are many promising innovations in this area, most of them are at the research stage. The benefits of bio-based plastics and better EoL options can be enjoyed only after increased production.

A Systematic Literature Review on Environmental Sustainability Issues of Flexible Packaging: Potential Pathways for Academic Research and Managerial Practice

The purpose of this review is to investigate environmental sustainability issues of the flexible packaging (FP) segment of the packaging industry. Increasingly, waste and pollution caused by FP have become a significant challenge for global sustainable development. Prior research studies have examined a diverse set of environmental challenges associated with FP, albeit, in a fragmented way. There is a paucity of research exploring and synthesizing the environmental burden of FP in an integrated fashion. To bridge this knowledge gap, we conducted a systematic literature review (SLR) to identify, synthesize, and analyze the environmental sustainability issues of FP utilizing the SCOPUS database. Based on an in-depth critical analysis of selected articles, this paper provides novel insights to scholars, practitioners, and policymakers for developing an improved understanding of environmental issues of the FP sector. This paper promotes academic scholarship and strengthens managerial practice in addressing the environmental sustainability challenges of FP.

Biofilm Formation Reduction by Eugenol and Thymol on Biodegradable Food Packaging Material

Biofilm is a structured community of microorganisms adhering to surfaces of various polymeric materials used in food packaging. Microbes in the biofilm may affect food quality. However, the presence of biofilm can ensure biodegradation of discarded packaging. This work aims to evaluate a biofilm formation on the selected biodegradable polymer films: poly (lactic acid) (PLA), poly (butylene adipate-co-terephthalate) (PBAT), and poly (butylene succinate) (PBS) by selected bacterial strains; collection strains of Escherichiacoli, Staphylococcusaureus; and Bacillus pumilus, Bacillussubtilis, Bacillustequilensis, and Stenotrophomonasmaltophilia isolated from dairy products. Three different methods for biofilm evaluation were performed: the Christensen method, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and fluorescence microscopy. High biofilm formation was confirmed on the control PBS film, whereas low biofilm formation ability was observed on the PLA polymer sample. Furthermore, the films with incorporated antimicrobial compounds (thymol or eugenol) were also prepared. Antimicrobial activity and also reduction in biofilm formation on enriched polymer films were determined. Therefore, they were all proved to be antimicrobial and effective in reducing biofilm formation. These films can be used to prepare novel active food packaging for the dairy industry to prevent biofilm formation and enhance food quality and safety in the future.

Synthesis, Properties, and Enzymatic Hydrolysis of Poly(lactic acid)-co-Poly(propylene adipate) Block Copolymers Prepared by Reactive Extrusion

Poly(lactic acid) (PLA) is a biobased polyester with ever-growing applications in the fields of packaging and medicine. Despite its popularity, it suffers from inherent brittleness, a very slow degradation rate and a high production cost. To tune the properties of PLA, block copolymers with poly(propylene adipate) (PPAd) prepolymer were prepared by polymerizing L-lactide and PPAd oligomers via reactive extrusion (REX) in a torque rheometer. The effect of reaction temperature and composition on the molecular weight, chemical structure, and physicochemical properties of the copolymers was studied. The introduction of PPAd successfully increased the elongation and the biodegradation rate of PLA. REX is an efficient and economical alternative method for the fast and continuous synthesis of PLA-based copolymers with tunable properties.

Biosynthesis of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from CO2 by a Recombinant Cupriavidusnecator

The copolyester of 3-hydroxybutyrate (3HB) and 3-hydoxyhexanoate (3HHx), PHBHHx, is one of the most practical kind of bacterial polyhydroxyalkanoates due to its high flexibility and marine biodegradability. PHBHHx is usually produced from vegetable oils or fatty acids through β-oxidation, whereas biosynthesis from sugars has been achieved by recombinant strains of hydrogen-oxidizing bacterium Cupriavidus necator. This study investigated the biosynthesis of PHBHHx from CO2 as the sole carbon source by engineered C. necator strains. The recombinant strains capable of synthesizing PHBHHx from fructose were cultivated in a flask using complete mineral medium and a substrate gas mixture (H2/O2/CO2 = 8:1:1). The results of GC and 1H NMR analyses indicated that the recombinants of C. necator synthesized PHBHHx from CO2 with high cellular content. When 1.0 g/L (NH4)2SO4 was used as a nitrogen source, the 3HHx composition of PHBHHx in the strain MF01∆B1/pBBP-ccrMeJ4a-emd was 47.7 ± 6.2 mol%. Further investigation demonstrated that the PHA composition can be regulated by using (R)-enoyl-CoA hydratase (PhaJ) with different substrate specificity. The composition of 3HHx in PHBHHx was controlled to about 11 mol%, suitable for practical applications, and high cellular content was kept in the strains transformed with pBPP-ccrMeJAc-emd harboring short-chain-length-specific PhaJ.

Synthesis of degradable and chemically recyclable polymers using 4,4-disubstituted five-membered cyclic ketene hemiacetal ester (CKHE) monomers

Novel degradable and chemically recyclable polymers were synthesized using five-membered cyclic ketene hemiacetal ester (CKHE) monomers. The studied monomers were 4,4-dimethyl-2-methylene-1,3-dioxolan-5-one (DMDL) and 5-methyl-2-methylene-5-phenyl-1,3-dioxolan-4-one (PhDL). The two monomers were synthesized in high yields (80-90%), which is an attractive feature. DMDL afforded its homopolymer with a relatively high molecular weight (M n >100 000, where M n is the number-average molecular weight). DMDL and PhDL were copolymerized with various families of vinyl monomers, i.e., methacrylates, acrylates, styrene, acrylonitrile, vinyl pyrrolidinone, and acrylamide, and various functional methacrylates and acrylate. Such a wide scope of the accessible polymers is highly useful for material design. The obtained homopolymers and random copolymers of DMDL degraded in basic conditions (in the presence of a hydroxide or an amine) at relatively mild temperatures (room temperature to 65 °C). The degradation of the DMDL homopolymer generated 2-hydroxyisobutyric acid (HIBA). The generated HIBA was recovered and used as an ingredient to re-synthesize DMDL monomer, and this monomer was further used to re-synthesize the DMDL polymer, demonstrating the chemical recycling of the DMDL polymer. Such degradability and chemical recyclability of the DMDL polymer may contribute to the circular materials economy.

Biodegradable polymers: A real opportunity to solve marine plastic pollution?

Plastic is a ubiquitous material in our life, and its durability represents a great problem for the environment. Several studies reported the occurrence of plastic litter in different environmental compartments and, consequently, numerous efforts are currently focused on how improving its recycling process and produce environmentally friendly solutions. In recent years, biodegradable polymers/plastics (BPs) have been proposed to reduce environmental impacts in specific applications (e.g., when conventional plastics are difficult or expensive to remove from the environment). Their wide use in commercial products, especially in the packaging sector, is causing new pollution alarm. Research studies are ongoing to improve BPs manufacturing and characteristics, but few data are reported about their behavior and toxicity into the marine environment. This paper reviewed the current state of the art highlighting that, even though the degradation of BPs in simulated or real marine environments is quite investigated, only eleven papers reported their effects on marine organisms (e.g., behavioral and oxidative stress and potential cascading effects on marine ecosystems). Presently, the main benefits of BPs are linked to waste management (including collection and recycling of organic waste). Due to the existing knowledge gaps, BPs cannot be deemed yet as a solution to marine plastic pollution.

Effect of Mineral Fillers on the Mechanical Properties of Commercially Available Biodegradable Polymers

In the successful transition towards a circular materials economy, the implementation of biobased and biodegradable plastics is a major prerequisite. To prevent the accumulation of plastic material in the open environment, plastic products should be both recyclable and biodegradable. Research and development actions in the past few decades have led to the commercial availability of a number of polymers that fulfil both end-of-life routes. However, these biobased and biodegradable polymers typically have mechanical properties that are not on par with the non-biodegradable plastic products they intend to replace. This can be improved using particulate mineral fillers such as talc, calcium carbonate, kaolin, and mica. This study shows that composites thereof with polybutylene succinate (PBS), polyhydroxybutyrate-hexanoate (PHBH), polybutylene succinate adipate (PBSA), and polybutylene adipate terephthalate (PBAT) as matrix polymers result in plastic materials with mechanical properties ranging from tough elastic towards strong and rigid. It is demonstrated that the balance between the Young’s modulus and the impact resistance for this set of polymer composites is subtle, but a select number of investigated compositions yield a combination of industrially relevant mechanical characteristics. Finally, it is shown that the inclusion of mineral fillers into biodegradable polymers does not negate the microbial disintegration of these polymers, although the nature of the filler does affect the biodegradation rate of the matrix polymer.