Biodegradability of Poly(vinyl acetate) and Related Polymers

Genetic Modifications in Bacteria for the Degradation of Synthetic Polymers: A Review

Synthetic polymers, commonly known as plastics, are currently present in all aspects of our lives. Although they are useful, they present the problem of what to do with them after their lifespan. There are currently mechanical and chemical methods to treat plastics, but these are methods that, among other disadvantages, can be expensive in terms of energy or produce polluting gases. A more environmentally friendly alternative is recycling, although this practice is not widespread. Based on the practice of the so-called circular economy, many studies are focused on the biodegradation of these polymers by enzymes. Using enzymes is a harmless method that can also generate substances with high added value. Novel and enhanced plastic-degrading enzymes have been obtained by modifying the amino acid sequence of existing ones, especially on their active site, using a wide variety of genetic approaches. Currently, many studies focus on the common aim of achieving strains with greater hydrolytic activity toward a different range of plastic polymers. Although in most cases the depolymerization rate is improved, more research is required to develop effective biodegradation strategies for plastic recycling or upcycling. This review focuses on a compilation and discussion of the most important research outcomes carried out on microbial biotechnology to degrade and recycle plastics.

Poly(Vinyl Acetate) Paints: A Literature Review of Material Properties, Ageing Characteristics, and Conservation Challenges

Since their development in the 1950s, poly(vinyl acetate) [PVAc] paints (also known as vinyl) have been used by many artists, most notably in countries such as Spain, Portugal, and the United Kingdom; they are also used globally as a common binder for house paints. However, only a relatively limited number of heritage scientific studies have focused on vinyl paints. Consequently, many critical aspects of this material, such as the degradation processes, variations in paint formulations, and responses to conservation treatments, remain largely understudied. This article aims to summarise the available relevant information on poly(vinyl acetate) paints from both the scientific and the conservation practice perspectives. The article provides a brief overview of the development of poly(vinyl acetate) paints as artist-grade and household products and the known differences in their formulations. It also focuses on poly(vinyl acetate) ageing behaviour, the physicochemical properties, the recent scientific research on poly(vinyl acetate) material characterisation and degradation, and the main conservation issues regarding these paints, such as those relating to cleaning treatments.

High-Barrier, Biodegradable Films with Polyvinyl Alcohol/Polylactic Acid + Wax Double Coatings: Influence of Relative Humidity on Transport Properties and Suitability for Modified Atmosphere Packaging Applications

Polyvinyl alcohol (PVOH) exhibits outstanding gas-barrier properties, which favor its use as a biodegradable, high-barrier coating on food-packaging films, possibly in combination with modified atmospheres. Nonetheless, its high sensitivity to water can result in a severe loss of barrier properties, significantly limiting its applications with fresh foods and in high-humidity conditions. In this work, the water vapor (PWV) and oxygen permeability (PO2) of high-barrier biodegradable films with PVOH/PLA + wax double coatings were extensively characterized in a wide range of relative humidity (from 30 to 90%), aimed at understanding the extent of the interaction of water with the wax and the polymer matrices and the impact of this on the permeation process. What is more, a mathematical model was applied to the PWV data set in order to assess its potential to predict the permeability of the multilayer films by varying storage/working relative humidity (RH) conditions. The carbon dioxide permeability (PCO2) of the films was further evaluated, and the corresponding permselectivity values were calculated. The study was finally augmented through modified atmosphere packaging (MAP) tests, which were carried out on double-coated films loaded with 0 and 5% wax, and UV-Vis analyses. The results pointed out the efficacy of the PLA + wax coating layer in hampering the permeation of water molecules, thus reducing PVOH swelling, as well as the UV-shielding ability of the multilayer structures. Moreover, the MAP tests underlined the suitability of the double-coated films for being used as a sustainable alternative for the preservation of foods under modified atmospheres.

Release efficiencies of potassium permanganate controlled-release biodegradable polymer (CRBP) pellets embedded in polyvinyl acetate (CRBP-PVAc) and polyethylene oxide (CRBP- PEO) for groundwater treatment

In-situ chemical oxidation (ISCO) is a commonly used method for the remediation of environmental contaminants in groundwater systems. However, traditional ISCO methods are associated with several limitations, including safety and handling concerns, rebound of groundwater contaminants, and difficulty in reaching all areas of contamination. To overcome these limitations, novel Controlled-Release Biodegradable Polymer (CRBP) pellets containing the oxidant KMnO₄ were designed and tested. The CRBP pellets were encapsulated in Polyvinyl Acetate (CRBP-PVAc) and Polyethylene Oxide (CRBP-PEO) at different weight percentages, baking temperatures, and time. Their release efficiency was tested in water, soil, and water and soil mixture media. Results showed that CRBP-PVAc pellets with 60 % KMnO₄ and baked at 120 °C for 2 min had the highest release percentage and rate across different conditions tested. Natural organic matter was also found to be an important factor to consider for in-field applications due to its potential reducing effect with Mn O 4 - . Overall, the use of CRBP pellets offers an innovative and sustainable solution to remediate contaminated groundwater systems, with the potential to overcome traditional ISCO limitations. These findings suggest that CRBP pellets could provide sustained and controlled release of the oxidant, reducing the need for multiple injections and minimizing safety and handling concerns. This study represents an important step towards developing a new and effective approach for ISCO remediation.

An integrated metagenomic model to uncover the cooperation between microbes and magnetic biochar during microplastics degradation in paddy soil

The free radicals released from the advanced oxidation processes can enhance microplastics degradation, however, the existence of microbes acting synergistically in this process is still uncertain. In this study, magnetic biochar was used to initiate the advanced oxidation process in flooded soil. paddy soil was contaminated with polyethylene and polyvinyl chloride microplastics in a long-term incubation experiment, and subsequently subjected to bioremediation with biochar or magnetic biochar. After incubation, the total organic matter present in the samples containing polyvinyl chloride or polyethylene, and treated with magnetic biochar, significantly increased compared to the control. In the same samples there was an accumulation of "UVA humic" and "protein/phenol-like" substances. The integrated metagenomic investigation revealed that the relative abundance of some key genes involved in fatty acids degradation and in dehalogenation changed in different treatments. Results from genome-centric investigation suggest that a Nocardioides species can cooperate with magnetic biochar in the degradation of microplastics. In addition, a species assigned to the Rhizobium taxon was identified as a candidate in the dehalogenation and in the benzoate metabolism. Overall, our results suggest that cooperation between magnetic biochar and some microbial species involved in microplastic degradation is relevant in determining the fate of microplastics in soil.

A realistic approach for the assessment of plastic contamination and its ecotoxicological consequences: A case study in the metropolitan city of Milan (N. Italy)

The study of the contamination of plastic mixtures sampled in natural environments is currently focused on their qualitative and quantitative assessment, while the evaluation of their effects on organisms is normally performed by experiments carried out at exposure conditions (size, shape, polymers) often far from the environmental ones. To improve the ecological realism, the aim of this study was to collect different plastic mixtures in 9 sampling stations located in 7 watercourses within the metropolitan city of Milan, one of the most anthropized and industrialized European areas, to evaluate both their qualitative and quantitative characteristics and, at the same time, to assess their ecotoxicological effects by exposing for 7 days some specimens of the freshwater bivalve Dreissena polymorpha to the mixtures collected in the sampling sites. The plastic characterization was performed by a Fourier-Transform Infrared spectrometer coupled with an optical microscope (μFT-IR), after several stages aimed to sample cleaning, separation of plastics and visual sorting. The possible effects caused by the plastic mixtures were carried out by the measurements of a biomarker suite to evaluate many cellular and molecular endpoints in mussel tissues. The main results showed a widespread and heterogeneous contamination of plastics in the entire metropolitan area, with contamination peaks found above all in the only two rivers of natural origin (Olona River and Lambro River) where comparable or higher values were reached than plastic concentrations measured in several European rivers. Despite this worrying contamination, the ecotoxicological data obtained after the exposures to the plastic mixtures collected in the selected water bodies showed only a mild effect on oxidative stress and on the variation of some antioxidant enzymes.

Assembly of 97 Novel Bacterial Genomes in the Microbial Community Affiliated with Polyvinyl Alcohol in Soil of Northern China

Background

Undeveloped ecosystems belong to rich source of microbial population, of which resources remain unearthed. A kind of polymeric compound system with high polyvinyl alcohol (PVA) content has been reported and named Taisui. Marker gene amplification showed that Taisui harbored little-explored microbial communities.

Aim

To address this issue, our study attempted to recover draft genomes and functional potential from microbial communities in Taisui using the metagenomic approach. Material and Methods. Taisui communities provided 97 novel bacterial genomes from 13 bacterial phyla, including bacteria candidate phylum. Two novel genus-level lineages were recovered from Planctomycetes and Chloroflexi. Based on the draft genomes, we expanded the number of taxa with potential productions of PKS and NRPS in phyla including Candidatus Dadabacteria, Chloroflexi, and Planctomycetes.

Results

A rich diversity of PVA dehydrogenase genes from 4 phyla, involving Proteobacteria, Acidobacteria, Acitinobacteria, and Planctomycetes, were identified. The phylogenetic tree of PVA dehydrogenase showed the possibility of horizontal gene transfer between microbes.

Conclusion

Our study underscores the substantial microbial diversity and PVA degradation potential in the previously unexplored Taisui system.

Rational Design of Sustainable Liquid Microcapsules for Spontaneous Fragrance Encapsulation

The high volatility, water-immiscibility, and light/oxygen-sensitivity of most aroma compounds represent a challenge to their incorporation in liquid consumer products. Current encapsulation methods entail the use of petroleum-based materials, initiators, and crosslinkers as well as mixing, heating, and purification steps. Hence, more efficient and eco-friendly approaches to encapsulation must be sought. Herein, we propose a simple method by making use of a pre-formed amphiphilic polymer and employing the Hansen Solubility Parameters approach to determine which fragrances could be encapsulated by spontaneous coacervation in water. The coacervates do not precipitate as solids but they remain suspended as colloidally stable liquid microcapsules, as demonstrated by fluorescence correlation spectroscopy. The effective encapsulation of fragrance is proven through confocal Raman spectroscopy, while the structure of the capsules is investigated by means of cryo FIB/SEM, confocal laser scanning microscopy, and small-angle X-ray scattering.

Green Polymerization of Vinyl Acetate Using Maghnite-Na+, an Exchanged Montmorillonite Clay, as an Ecologic Catalyst

In this work, the green polymerization of vinyl acetate is carried out by a new method which consists in the use of clay called Maghnite-Na+ as an ecological catalyst, non-toxic, inexpensive and recyclable by a simple filtration. X-ray diffraction and scanning electron microscopy showed that Maghnite-Na+ is successfully obtained after cationic treatment (sodium) on crude maghnite. It is an effective alternative to replace toxic catalysts such as benzoyl peroxide and azobisisobutyronitrile which are mostly used during the synthesis of polyvinyl acetate (PVAc) making the polymerization reaction less problematic for the environment. The synthesis reaction is less energetic by the use of recycled polyurethane as a container for the reaction mixture and is considered as a renewable material and a good thermal insulator maintaining the temperature of 273 K for 6 h. The reaction in bulk is also preferred to avoid the use of a solvent and therefore to stay in the context of green chemistry. In these conditions, the structure of obtained polymer is established by 1H NMR and 13C NMR. Infrared spectroscopy (FT-IR) was also used to confirm the structure of PVAc. Thermogravimetric analysis showed that it is thermally stable and starts to degrade at 603 K while differential scanning calorimetry showed that this polymer has a glass transition temperature Tg of 323 K.

A novel esterase DacApva from Comamonas sp. strain NyZ500 with deacetylation activity for acetylated polymer polyvinyl alcohol

As a water-soluble polymer, the widely used polyvinyl alcohol (PVA) is produced from hydrolysis of polyvinyl acetate. Microbial PVA carbon backbone cleavage via a two-step reaction of dehydrogenation and hydrolysis has been well studied. Content of acetyl group is a pivotal factor affecting performance of PVA derivatives in industrial application, and deacetylation is a non-negligible part in PVA degradation. However, the genetic and biochemical studies of its deacetylation remain largely elusive. Here, Comamonas sp. strain NyZ500 was isolated for its capability of growing on acetylated PVA from activated sludge. A spontaneous PVA-utilization deficient mutant strain NyZ501 was obtained when strain NyZ500 was cultured in rich media. Comparative analysis between the genomes of these two strains revealed a fragment (containing a putative hydrolase gene dacA_pva ) deletion in NyZ501 and dacA_pva-complemented strain NyZ501 restored the ability to grow on PVA. DacA_pva, which shares 21% identity with xylan esterase AxeA1 from Prevotella ruminicola 23, is a unique deacetylase catalyzing the conversion of acetylated PVA and its derivatives to deacetylated counterparts. This indicates that strain NyZ500 utilizes acetylated PVA via acetate as a carbon source to grow. DacA_pva also possessed the deacetylation ability for acetylated xylan and the antibiotic intermediate 7-aminocephalosporanic acid (7ACA) but the enzymes for the above two compounds had no activities against PVA derivatives. This study enhanced our understanding of the diversity of microbial degradation of PVA and DacA_pva characterized here is also a potential biocatalyst for the eco-friendly biotransformation of PVA derivatives and other acetylated compounds.IMPORTANCE: Water-soluble PVA, which possesses a very robust ability to accumulate in the environment, has a very grave environmental impact due to its widespread use in industrial and household applications. On the other hand, chemical transformation of PVA derivatives is currently being carried out at high energy consumption and high pollution conditions using hazardous chemicals (such as NaOH, methanol) under high temperatures. The DacA_pva reported here performs PVA deacetylation under mild conditions, then it has a great potential to be developed into an eco-friendly biocatalyst for biotransformation of PVA derivatives. DacA_pva also has deacetylation activity for compounds other than PVA derivatives, which facilitates its development into a broad-spectrum deacetylation biocatalyst for production of certain desired compounds.

Biodegradability of Polyvinyl Alcohol Based Film Used for Liquid Detergent Capsules

Questions and potential misperceptions have arisen about the potential contribution of liquid detergent capsules to the environmental microplastics issue. The film of these detergents is highly water soluble, also in cold water, as it must fully dissolve during every type of washing process. Water-soluble grades of polyvinyl alcohol, the most commonly used detergent capsule film material, are recognised to be biodegradable. In the current paper, adequate biodegradability is confirmed by means of ready biodegradation screening tests, across a range of polyvinyl alcohol detergent grade films. The high water solubility in itself implies that detergent capsule films are not within the microplastic scope. Furthermore, their biodegradability ensures there is no concern for persistence or accumulation in the environment.

Tuning the Encapsulation of Simple Fragrances with an Amphiphilic Graft Copolymer

The encapsulation of poorly water-soluble compounds such as perfumes, flavors, and bioactive molecules is a key step in the formulation of a large variety of consumer products in the fields of household care and personal care. We study the encapsulation ability of an amphiphilic poly(ethylene glycol)-graft-poly(vinyl acetate) (PEG-g-PVAc) graft copolymer, extending the focus to the entire phase diagram of polymer/perfume/water systems with three common natural fragrances. The three perfume molecules (2-phenyl ethanol, L-carvone, and α-pinene) possess different water affinities, as expressed by their octanol/water partition coefficients. The investigation of the polymorphism of PEG-g-PVAc in these systems is carried out by means of dynamic light scattering, small-angle X-ray scattering, NMR spectroscopy, and confocal laser scanning microscopy. The results presented here demonstrate that the choice of fragrance can dramatically affect the supramolecular structures formed by the polymer in aqueous solution, with important consequences on formulations of industrial interest such as the demixing of complex perfume blends when one or more of the components have no chemical affinity for any of the polymer blocks.

Basalt-Fiber-Reinforced Polyvinyl Acetate Resin: A Coating for Ductile Plywood Panels

The aim of this study was to create a reinforced composite wood-based panel that would be leaned towards the environment Plywood was used as a core material and fiber-reinforced polymer was used as a reinforcement. Conventional resin for the fiber-reinforced polymer was substituted with polyvinyl acetate (PVAC), which has several advantages, such as a lower price, easier handling, and better degradability. The second chosen component, basalt fiber, is cost attractive and environmentally friendly. The combination of one and two layers of fabric with three fiber fractions and 4 mm thick plywood was investigated. The best results were achieved with two layers of fabric and the highest fiber fraction. The improvements of the ultimate bending load and bending stiffness of the plywood in the perpendicular direction were 305% and 325%, respectively. The ultimate load and stiffness of the parallel direction were improved by 31% and 35%, respectively. However, specimens always failed in the compressional zone. The highest reinforcing effect was found with the impact test: The energy required to fracture specimens increased by 4213% and 6150% for one and two layers of fabric, respectively. In conclusion, specimens exhibited high ductility due to the PVAC and basalt fiber. The amount of work and energy required to cause fractures was extensive.

Maskless Patterning of Biodegradable Conductors by Selective Laser Sintering of Microparticle Inks and Its Application in Flexible Transient Electronics

Biodegradable electronic devices are able to break down into benign residues after their service life, which may effectively alleviate the environmental impacts as a consequence of the proliferation of consumer electronic technology. The widespread adaptation to biodegradable systems is currently impeded by the lack of economic fabrication techniques for functional devices. Here, a facile approach to generate a biodegradable conductor is developed based on selective laser sintering of zinc and iron microparticle ink. The sintering process is effective to convert naturally oxidized microparticles into interconnected conductors. Arbitrary conductive features are readily created over flexible biodegradable substrates under ambient conditions, which exhibits excellent conductivity (∼2 × 10⁶ S m^-1), low sheet resistance (∼0.64 Ω □ ^- 1), fine feature resolution (∼45 μm), and mechanical flexibility. The practical suitability is demonstrated by fabricating a miniaturized near-field communication tag with the dimension to mount on the fingernail. The methodology is further extended to create a metallic grid as a biodegradable transparent electrode with low sheet resistance (2.5 Ω □^-1) and high optical transmittance (96%), which is employed as an epidermal transparent heater for thermotherapy. Maskless patterning of biodegradable conductors may find a broad range of applications in environment friendly gadgets and implantable medical devices.

Polyvinyl acetate processing wastewater treatment using combined Fenton's reagent and fungal consortium: Application of central composite design for conditions optimization

The Fenton reaction as an oxidative degradation process was used for industrial chemical wastewater (ICW) pretreatment. The biodegradation of pretreated ICW was performed, in aqueous environment under aerobic condition, by a defined fungal consortium. The central composite design (CCD) was used to study the effect of nitrogen and phosphorus addition and the concentration of the pollution on the removal of polyvinyl alcohol (PVA) and organic compounds. The interaction between parameters was modeled using the response surface methodology (RSM). Results of optimization showed COD, PVA and color removal yields of 97.8%, 98.5% and 99.75%, respectively with a supplementof 1.4 gL^-1 of (NH₄)₂SO₄, 1.2 gL^-1 of KH₂PO₄ and 75% of concentrated ICW. Enzymatic analysis proved that laccase and lignin peroxidase were involved in the biodegradation with 45 UIL^-1 and 450 UIL^-1, respectively. Furthermore, the analysis of metabolic products using Fourier transforms infrared spectroscopy (FTIR) and nuclear magnetic resonance (¹HNMR) showed clearly the mineralization of organic compounds and the formation of formic acid and ethanol. Therefore, the effective treatment of ICW was achieved by developing an integrated chemical and biological process which met the requirement for a safety effluent respectful for environment without risks for public health.

Seaweed-derived polymeric materials for multiapplications including marine algal cultivation

This study described the preparation of phycocolloids based polymeric materials for multiapplications including seaweed cultivation in open sea water conditionsviagrafting reaction of phycocolloids with vinyl acetate (VAc).

Lignocellulosic biomass: a sustainable platform for the production of bio-based chemicals and polymers

The ongoing research activities in the field of lignocellulosic biomass for production of value-added chemicals and polymers that can be utilized to replace petroleum-based materials are reviewed.

Potential of Ophiostoma piceae sterol esterase for biotechnologically relevant hydrolysis reactions

The ascomycete Ophiostoma piceae produces a sterol esterase (OPE) with high affinity toward p-nitrophenol, glycerol, and sterol esters. Recently, this enzyme has been heterologously expressed in the methylotrophic yeast Pichia pastoris under the AOX1 methanol-inducible promoter (PAOX1) using sorbitol as co-susbtrate, and the hydrolytic activity of the recombinant protein (OPE*) turned out to be improved from a kinetic point of view. In this study, we analyze the effects of sorbitol during the expression of OPE*, at first added as an additional carbon source, and methanol as inducer. The O. piceae enzyme was successfully used for PVAc hydrolysis, suggesting its potential applicability in recycled paper production to decrease stickies problems.