Degradation Of Polylactic Acid Research Articles

The degradation of polylactic acid face mask components in different environments

The disposal of fossil fuel-based plastics poses a huge environmental challenge, leading to increased interest in biodegradable alternatives such as polylactic acid (PLA). This study focuses on the environmental impact and degradation of PLA face mask components under various conditions (UV (Ultraviolet) radiation, DI water, landfill leachate of various ages, seawater, and enzyme). Under UV exposure, notable changes in physicochemical properties were observed in the PLA masks, including increased oxidation over time. Degradation rates varied across environments, with old landfill leachate and enzyme degradation having a notable impact, especially on meltblown layers. Furthermore, it was found that seawater conditions hampered the degradation of PLA masks, likely due to the inhibitory effect of high salt concentrations. The pathways of chemical group changes during degradation were elucidated using 2D-COS (Two-Dimensional Correlation Spectroscopy) maps. The investigation into the release of microparticles and oligomers further revealed the degradation mechanism. Moreover, PLA masks were found to release fewer microparticles when degraded in studied environments when compared to traditional polypropylene masks. Furthermore, correlation analysis highlighted the influence of factors such as carbonyl index and contact angle on degradation rates, underscoring the complex interplay between environmental conditions and PLA degradation. This comprehensive investigation advances the understanding of PLA degradation pathways, which are crucial for mitigating plastic pollution and promoting the development of sustainable products.

Assessing the Stability and Photocatalytic Efficiency of a Biodegradable PLA‐TiO2 Membrane for Air Purification

AbstractThe potential of a biodegradable polylactic acid (PLA)‐TiO2 membrane for air purification is investigated, utilizing the environmentally friendly solvent Cyrene. Through the integration of TiO2 nanoparticles within a PLA matrix, the membrane is used to degrade ethanol as a model volatile organic compound (VOC) under UV light. Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray Analysis (EDX), and UV–vis spectrophotometry confirm the porous structure of the membrane, the even distribution of TiO2, and its effective band gap of 3.06 eV, respectively. Ethanol adsorption is best described by the Langmuir isotherm model, suggesting monolayer coverage on a homogeneous surface. Photocatalytic tests demonstrate that the membrane decomposes ethanol (6800 ppm) within 14 min under UV light, generating acetaldehyde, acetic acid, formaldehyde, and formic acid as intermediates, and ultimately producing CO2 and water. Reusability tests indicate a decrease in decomposition time over successive cycles due to increased TiO2 exposure from the gradual degradation of PLA. However, this degradation poses challenges for continuous use, compromising the membrane's long‐term durability.

Impact of biological environment on bending fatigue lifetime in additive-manufactured polylactic acid fabricated by 3D-printing

Polylactic acid (PLA) has become desirable for biomedical applications, particularly implantable devices. However, the degradation of PLA in biological environments under mechanical stress remains incompletely understood and requires further investigation. This study compared the plain fatigue (PF) and the biodegraded fatigue (BDF) behavior of 3D-printed PLA. For this purpose, two sets of standard fatigue specimens were additively manufactured by the fused filament fabrication (FFF) method. One set was used for plain fatigue testing, and the other was immersed for 330 days in simulated body fluid (SBF). After immersion, the samples were dried and weighed before fatigue testing. The fully reversed rotary bending fatigue tests were conducted on both sets of specimens, and the stress-lifetime (S-N) curves were obtained. Additionally, the fatigue properties of PF and BDF specimens were evaluated. Moreover, the fracture behaviors of the materials were studied using field emission scanning electron microscopy (FESEM). The outcomes implied that the weight of the samples extended during the immersion period, primarily due to water absorption by the PLA. However, after drying, the final weights did not change compared to the weights before immersion. The SBF immersion significantly reduced the fatigue performance of the biodegraded samples comparing the PF result.

Mechanical and failure behaviour of PLA FFF printed part under sweat absorption: Splint arm application

This study focuses on the selection of printing parameters for arm splint to support forces under sweat exposure. We investigated the influence of varying infill density and raster angle on flexural properties after sweat diffusion. In particular, polylactic acid (PLA) beams were printed in the edge direction with different infill densities (60%, 80% and 100%) and raster angles (0°, 45° and 90°). We evaluated the flexural properties of the beams before and after aging in sweat, and analysed the failure mode based on the printing parameters. Additionally, we quantified the porosity of the samples and correlated it with sweat absorption and mechanical properties. Degradation of PLA in water and sweat is assessed by the Fourier transform infrared spectroscopy analysis. Our findings revealed that a higher strength and stiffness were achieved with a 45° raster angle and higher infill density. Interestingly, the parameters that resulted in optimal properties before and after sweat absorption aren’t the same. Sweat absorption depends on the architecture leads to the change in failure mode which initiated fracture. The findings provide valuable insights into the optimisation of printing parameters for arm splints, considering both mechanical performance and the impact of sweat interaction on fracture behaviour.

Decomposition and fragmentation of conventional and biobased plastic wastes in simulated and real aquatic systems

AbstractPlastics play a crucial role in our daily lives. The challenge, however, is that they become waste and contribute to a global environmental problem, increasing concerns about pollution and the urgent need to protect the environment. The accumulation and fragmentation of plastic waste, especially micro- and nanoplastics in aquatic systems, poses a significant threat to ecosystems and human health. In this study, the decomposition and fragmentation processes of conventional and biobased plastic waste in simulated water bodies (waters with different pH values) and in real water systems (tap water and seawater) are investigated over a period of one and six months. Three types of plastic were examined: thermoplastic polyethylene terephthalate and thermoset melamine etherified resin in the form of nonwovens and biobased polylactic acid (PLA) in the form of foils. Such a comprehensive study involving these three types of plastics and the methodology for tracking degradation in water bodies has not been conducted before, which underlines the novelty of the present work. After aging of the plastics, both the solid fraction and the leachate in the liquid phase were carefully examined. The parameters studied include mass loss, structural changes and alterations in functional groups observed in the aged plastics. Post-exposure assessment of the fragmented pieces includes quantification of the microplastic, microscopic observations and confirmation of composition by in situ Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy. The leachate analysis includes pH, conductivity, turbidity, total carbon and microplastic size distribution. The results highlight the importance of plastic waste morphology and the minor degradation of biobased PLA and show that microfibers contribute to increased fragmentation in all aquatic systems and leave a significant ecological footprint. This study underlines the crucial importance of post-consumer plastic waste management and provides valuable insights into strategies for environmental protection. It also addresses the pressing issue of plastic pollution and provides evidence-based measures to mitigate its environmental impact. Graphical abstract

Dyeability and hydrolytic degradation of polylactic acid fibers under different environments

Polylactic acid (PLA), a biodegradable material derived from industrial crops such as corn and straw, is increasingly recognized in various sectors, including textiles, food, and medicine. However, the dyeability and biodegradability of PLA a key factor contributing to its growing popularity. Herein, we report a sustainable dyeing method for the coloration of PLA fibers with excellent fastness using dispersed dyes. The results showed that the dyed PLA fabric exhibited a K/S value of 8.4, along with impressive grade 4 fastness to both dry and wet rubbing. Additionally, the dyed PLA fabric exhibited increased hydrophilicity and enhanced surface roughness. Most importantly, during the hydrolytic degradation experiment, the dyed polylactic acid fabric experienced a notable 36 % decrease in quality when exposed to a water environment characterized by a pH of 11, a temperature of 40 °C, and a duration of 60 days, whereas the control PLA fabric is only 8 %. The hydrolytic degradation of PLA occurs at its fastest rate when the color of the dye is at its optimal intensity, the environmental temperature is elevated, and the pH level is in an alkaline state. The degradation rate of PLA fabric initially tends to be rapid, followed by a gradual slowdown. This research may provide a useful guideline for the proper storage of dyed PLA fabrics and their use in the textile industry.

The study of degradation and mechanical properties of poly(lactic) acid (PLA) based 3D printed filament

Additive manufacturing, commonly known as 3D printing technology, has become one of the mainstream processes in the manufacturing industry due to its advantages over conventional manufacturing, which have piqued the public’s interest. This study aims to focus on the influence of thermal conditions on crystallization towards mechanical properties of 3D printed poly(lactic) acid (PLA) degradation samples with 100% infill. As for the degradation profile, the highest weight loss recorded by the samples was 0.7%, observed in samples buried in soil with an abiotic medium for one month. The exposure of degraded samples to high temperature during drying affected their crystallinity, resulting in significant changes in strains, particularly between week 1 and week 2, where strains dropped significantly from 7.33% to 4.28%, respectively. In conclusion, it has been demonstrated that degradation for PLA material still can occur in an abiotic medium, albeit at a slower rate compared to a biotic medium due to the presence of additional microorganisms and bacteria. Besides, the post-heat treatment process on PLA degradation samples affects their crystalline structure, resulting in significant changes in mechanical properties, particularly especially strains. Therefore, it can be concluded that different materials exhibit distinct mechanical properties.

Effect of Oligoricinoleic Acid on Degradation of Polylactic Acid

ABSTRACT The objective of this research is to explore the impact of oligoricinoleic acid (ORA) on the degradation of polylactic acid (PLA). ORA was synthesized from ricinoleic acid using tin (II) 2-ethylhexanoate as a catalyst. The chemical structures of the obtained ORA were confirmed by Fourier-transform infrared spectrometer (FT-IR) and proton nuclear magnetic resonance spectroscopy (1H-NMR). PLA/ORA films were prepared through the casting method by varying ORA concentrations as 0.1%wt, 0.3%wt, 0.5%wt, 1.0 wt%, and 3.0%wt. Degradation of the films via hydrolysis was studied by soaking the films in deionized water and stirring at 120 rpm in an incubator at 37°C. Alterations in the structure and properties of the films were investigated after soaking for 7, 14, 21, and 28 days using ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectrometer (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and universal testing machine (UTM). Gel permeation chromatography (GPC) was performed to confirm the decrease in molecular weight (MW). The presence of 3%wt ORA could promote both ductility and degradation of PLA films. ORA further enhances thermal stability, indicating potential for prevention of thermal degradation during melt processing.

Landfill-mined soil-like fraction (LMSF) use in biopolymer composting: Material pre-treatment, bioaugmentation and agricultural prospects

Polylactic Acid (PLA) based compostable bioplastic films degrade under thermophilic composting conditions. The purpose of our study was to understand whether sample pre-treatment along with bioaugmentation of the degradation matrix could reduce the biodegradation time under a simulated composting environment. Sepcifically, we also explored whether the commercial composts could be replaced by landfill-mined soil-like fraction (LMSF) for the said application. The effect of pre-treatment on the material was analysed by tests like tensile strength analysis, hydrophobicity analysis, morphological analysis, thermal degradation profiling, etc. Subsequently, the degradation experiment was performed in a simulated composting environment following the ASTM D5338 standard, along with bioaugmentation in selected experimental setups. When the novel approach of material pre-treatment and bioaugmentation were applied in combination, the time necessary for 90% degradation was reduced by 27% using compost and by 23% using LMSF. Beyond the improvement in degradation rate, the water holding capacity increased significantly for the degradation matrices. With pH, C: N ratio and microbial diversity tested to be favourable through 16s metabarcoding studies, material pre-treatment and bioaugmentation allow LMSF to not only replace commercial compost in polymer degradation but also find immense application in the agricultural sector of drought-affected areas (for better water retention) after it has been used for PLA degradation.

Degradation efficiency of biodegradable plastics in subtropical open-air and marine environments: Implications for plastic pollution

Bioplastics are increasingly used as a solution to tackle plastic pollution problems. However, their degradability in natural environments is currently under debate. To evaluate their degradation efficiencies, we conducted in-situ degradation experiments in an open-air and two marine environments in Hong Kong. Three groups of biodegradable plastic were tested, namely (1) additive-modified low-density polyethylene (LDPE), labelled as oxo-biodegradable or photodegradable plastics, (2) polylactic acid (PLA), and (3) polyvinyl alcohol (PVA)/starch blends. Most biodegradable plastics fail to completely degrade but remain visually present after six months of exposure. Only PLA is able to demonstrate 100 % disintegration in one to three months in marine settings, suggesting that subtropical marine environments may favor PLA degradation. Biodegradable plastics that are bio-based (PLA and PVA/Starch blends) show notably larger mass losses by 23–100 % than the fossil-based ones (modified-LDPE). Our results reveal higher degradation efficiencies of PLA and PVA/Cassava starch blend in marine than open-air settings (with mass losses larger by 50 %, and by 39–41 %, respectively), potentially via biodegradation and hydrolysis. Meanwhile, modified-LDPE and PVA/Corn starch blends in general show higher degradation efficiencies in open-air than marine settings (with mass losses larger by 2 %, and by 17–33 %, respectively), potentially via abiotic oxidation. Since all tested biodegradable plastics exhibit potential fragmentation signs, further investigation is needed to characterize the behaviours of the microplastics generated. The current labelling on biodegradable bags fails to provide comprehensive information regarding their actual environmental degradation behaviours, especially considering their fragmentation risk and limited degradation exhibited in this study. This highlights the imperative for improved messaging to ensure consumers are better informed about these products.

Confined Water Dynamics in the Scaffolds of Polylactic Acid.

Resorbable polylactic acid (PLA) ultrathin fibers have been applied as scaffolds for tissue engineering applications due to their micro- and nanoporous structure that favor cell adhesion, besides inducing cell proliferation and upregulating gene expression related to tissue regeneration. Incorporation of multiwalled carbon nanotubes into PLA fibers has been reported to increase the mechanical properties of the scaffold, making them even more suitable for tissue engineering applications. Ideally, scaffolds should be degraded simultaneously with tissue growth. Hydration and swelling are factors related to scaffold degradation. Hydration would negatively impact the mechanical properties since PLA shows hydrolytic degradation. Water absorption critically affects the catalysis and allowance of the hydrolysis reactions. Moreover, either mass transport and chemical reactions are influenced by confined water, which is an unexplored subject for PLA micro- and nanoporous fibers. Here, we probe and investigate confined water onto highly porous PLA microfibers containing few amounts of incorporated carbon nanotubes by Fourier transform infrared (FTIR) spectroscopy. A hydrostatic pressure was applied to the fibers to enhance the intermolecular interactions between water molecules and C=O groups from polyester bonds, which were evaluated over the wavenumber between 1600 and 2000 cm-1. The analysis of temperature dependence of FTIR spectra indicated the presence of confined water which is characterized by a non-Arrhenius to Arrhenius crossover at T0 = 190 K for 1716 and 1817 cm-1 carbonyl bands of PLA. These bands are sensitive to a hydrogen bond network of confined water. The relevance of our finding relies on the challenge detecting confined water in hydrophobic cavities as in the PLA one. To the best of our knowledge, we present the first report referring the presence of confined water in a hydrophobic scaffold as PLA for tissue engineering. Our findings can provide new opportunities to understand the role of confined water in tissue engineering applications. For instance, we argue that PLA degradation may be affected the most by confined water. PLA degradation involves hydrolytic and enzymatic degradation reactions, which can both be sensitive to changes in water properties.

Study on the long-range chain degradation behavior of polylactic acid promoted by nanometer zinc oxide

Polylactic acid (PLA) is known for its degradative properties. Since PLA possesses a long chain macromolecular structure, its degradation behavior and characteristics have been the focus of research. In the presence of Lewis acid, the carbonyl oxygen in the ester group of PLA molecular chain can coordinate with it and be activated, so as to break the ester group and cause PLA degradation. However, there is still a lack of research strategies on the evolution of the remote structure of PLA chains, and there were few studies on the long-range degradation of PLA molecular chain in the effect of Lewis acid. In this work, a statistical method, combined with molecular weight testing, was proposed to investigate the long-range degradation behavior of PLA molecular chains. Results showed that in the presence of nano-ZnO, the long-range degradation of PLA molecular chain in solution was initially carried out in the form of terminal group biting-back and exchanging within 4 hours, and the molecular chain with new terminal-group was still long enough after degradation, gradually shortened over time. PLA began to degrade obviously after 8 h reaction. This chain scission method can provide a reaction platform for some reactions such as long-chain branching, which can be utilized to prepare PLA with special molecular chain topology and explore the mechanism of PLA chain structure transformation.

Electrochemical investigations of PLA coatings deposited by fused filament fabrication on magnesium alloy in Ringer's solution

In this paper, polylactic acid (PLA) layers were printed on AM60 magnesium alloy through a fused filament fabrication-3D printing manufacturing method, as a low-cost and innovative technology. Then, the effect of coating thickness and anodized layer as a binder on the electrochemical behavior of Mg substrates was investigated in Ringer's solution. Electrochemical impedance spectroscopy, Tafel polarization, and weight loss investigations were performed at various exposure times for 28 days to achieve this purpose. Corroded surfaces were also analyzed through field emission scanning electron microscopy images and Fourier-transform infrared spectroscopy patterns. The obtained results showed that the higher thickness of the layer with a value of 400 µm was not effective in raising the PLA layer impedance without the anodized layer. However, the higher PLA thickness could have a key role in the corrosion rate reduction of PLA layers when printed on the anodized layer. The lowest corrosion rate with a value of 0.3 µA/cm2 was related to the PLA-printed layer with a lower thickness (200 µm) and without an anodized layer. This reduction range in corrosion current density was about 80.2–99.4 % compared to the Mg alloy. The weight loss behavior of PLA layers during a long time of exposure was followed by a logarithmic function. The range of corrosion rate decrease was 9.7–32.2 %. The PLA degradation mechanism was also suggested based on all obtained results.

Synthesis of Poly-Lactic Acid by Ring Open Polymerization from Beer Spent Grain for Drug Delivery.

Poly-lactic acid (PLA) is a synthetic polymer that has gained popularity as a scaffold due to well-established manufacturing processes, predictable biomaterial properties, and sustained therapeutic release rates. However, its drawbacks include weak mechanical parameters and reduced medicinal delivery efficacy after PLA degradation. The development of synthetic polymers that can release antibiotics and other medicines remains a top research priority. This study proposes a novel approach to produce PLA by converting Brewer's spent grain (BSG) into lactic acid by bacterial fermentation followed by lactide ring polymerization with a metal catalyst. The elution properties of the PLA polymer are evaluated using modified Kirby-Bauer assays involving the antimicrobial chemotherapeutical, trimethoprim (TMP). Molded PLA polymer disks are impregnated with a known killing concentration of TMP, and the PLA is evaluated as a drug vehicle against TMP-sensitive Escherichia coli. This approach provides a practical means of assessing the polymer's ability to release antimicrobials, which could be beneficial in exploring new drug-eluting synthetic polymer strategies. Overall, this study highlights the potential of using BSG waste materials to produce valuable biomaterials of medical value with the promise of expanded versatility of synthetic PLA polymers in the field of drug-impregnated tissue grafts.

Hydrolytic degradation and biodegradation of polylactic acid electrospun fibers

Increased use of bioplastics, such as polylactic acid (PLA), helps in reducing greenhouse gas emissions, decreases energy consumption and lowers pollution, but its degradation efficiency has much room for improvement. The degradation rate of electrospun PLA fibers of varying diameters ranging from 0.15 to 1.33 μm is measured during hydrolytic degradation under different pH from 5.5 to 10, and during aerobic biodegradation in seawater supplemented with activated sewage sludge. In hydrolytic conditions, varying PLA fiber diameter had significant influence over percentage weight loss (W%L), where faster degradation was achieved for PLA fibers with smaller diameter. W%L was greatest for PLA-5 > PLA-12 > PLA-16 > PLA-20, with average W%L at 30.7%, 27.8%, 17.2% and 14.3% respectively. While different pH environment does not have a significant influence on PLA degradation, with W%L only slightly higher for basic environments. Similarly biodegradation displayed faster degradation for small diameter fibers with PLA-5 attaining the highest degree of biodegradation at 22.8% after 90 days. Hydrolytic degradation resulted in no significant structural change, while biodegradation resulted in significant hydroxyl end capping products on the PLA surface. Scanning electron microscopy (SEM) imaging of degraded PLA fibers showed a deteriorated morphology of PLA-5 and PLA-12 fibers with increased adhesion structures and irregularly shaped fibers, while a largely unmodified morphology for PLA-16 and PLA-20.

Magnesium Hydroxide as a Versatile Nanofiller for 3D-Printed PLA Bone Scaffolds.

Polylactic acid (PLA) has attracted much attention in bone tissue engineering due to its good biocompatibility and processability, but it still faces problems such as a slow degradation rate, acidic degradation product, weak biomineralization ability, and poor cell response, which limits its wider application in developing bone scaffolds. In this study, Mg(OH)2 nanoparticles were employed as a versatile nanofiller for developing PLA/Mg(OH)2 composite bone scaffolds using fused deposition modeling (FDM) 3D printing technology, and its mechanical, degradation, and biological properties were evaluated. The mechanical tests revealed that a 5 wt% addition of Mg(OH)2 improved the tensile and compressive strengths of the PLA scaffold by 20.50% and 63.97%, respectively. The soaking experiment in phosphate buffered solution (PBS) revealed that the alkaline degradation products of Mg(OH)2 neutralized the acidic degradation products of PLA, thus accelerating the degradation of PLA. The weight loss rate of the PLA/20Mg(OH)2 scaffold (15.40%) was significantly higher than that of PLA (0.15%) on day 28. Meanwhile, the composite scaffolds showed long-term Mg2+ release for more than 28 days. The simulated body fluid (SBF) immersion experiment indicated that Mg(OH)2 promoted the deposition of apatite and improved the biomineralization of PLA scaffolds. The cell culture of bone marrow mesenchymal stem cells (BMSCs) indicated that adding 5 wt% Mg(OH)2 effectively improved cell responses, including adhesion, proliferation, and osteogenic differentiation, due to the release of Mg2+. This study suggests that Mg(OH)2 can simultaneously address various issues related to polymer scaffolds, including degradation, mechanical properties, and cell interaction, having promising applications in tissue engineering.

A phenomenological model of pulsatile blood pressure-affected degradation of polylactic acid (PLA) vascular stent.

The stent implantation may alter the post-operative patient's blood pressure, and bioresorbable vascular stents (BVS) as a candidate to treat vascular diseases, its degradation is affected by mechanical stress, thus, the altered pressure representing varying stress level will result in different degradation behaviors of the BVS. This paper first proposed a novel stress-regulated PLA degradation model that included swelling factor, and then the degradation evolutions of a PLA BVS within 180days under normal and high blood pressures were simulated by finite element method, and more four degradation indexes were defined to study the effects of the two blood pressures on the degradation of the PLA BVS. The results showed that the high pressure weakly accelerated the degradation of the PLA BVS with respect to the normal pressure by examining the four indexes, e.g., the residual stent volume decreased to 0.72 and 0.69, respectively for the normal and high pressures at day 180. The current finding provided a theoretical understanding of the PLA BVS degradation, and hinted that the PLA BVS may not need to be elaborately selected in clinical practices for treating hypertensive patients.

Optimization of the Degradation Processes for Polylactic Acid using Microbial Enzymes: A Brief Summary

Polylactic acid (PLA) has emerged as a desirable bioplastic due to its production from renewable materials and biodegradability. However, its low toughness and fragility limit its applications, prompting the blending of PLA with other biopolymers to enhance its properties. As the global demand for bioplastics increases, efficient processes for PLA degradation are needed to match the high rate of plastic production. Chemical, microbial, and enzymatic processing are the major methods of PLA degradation, with enzymatic processing being environmentally friendly and sustainable. recyclable products like lactic acid can also be recovered. This creates a need to determine suitable enzymes that can hydrolyze polylactic acid. PLA exhibits high resistance to direct microbial degradation, making microbial enzymatic processing a more attractive alternative. Microbial enzymes, including proteases, lipases, esterases, and cutinases, have shown potential for PLA degradation. Nevertheless, current research on the enzymatic degradation of PLA needs comprehensive studies on optimal processes, conditions, and influencing factors. This review aims to address this gap by examining microbial enzymes and their processes for the enzymatic degradation of PLA. Findings indicate that microbial enzymes like proteinase K, Savinase, and Alcalase show promise for efficient PLA degradation under optimized conditions. Further research should, therefore, focus on exploring these enzymes further, refining enzymatic degradation processes, exploring genetic modifications of these enzymes, and developing sustainable recycling methods to advance bioplastics like PLA and address plastic pollution challenges effectively.
 
 Keywords: Polylactic acid; enzymatic degradation; microbial enzymes; optimization; bioplastic; biodegradability; plastic pollution; bioremediation.

Humic substance/metal-oxide multifunctional nanoparticles as advanced antibacterial-antimycotic agents and photocatalysts for the degradation of PLA microplastics under UVA/solar radiation

As a result of the accumulation of plastic in the environment, microplastics have become part of the food chain, boosting the resistance of fungi and bacteria which can frequently encounter human beings. Employing photocatalytic degradation is a possible route towards the removal of chemical and biological pollutants, such as plastics and microplastic wastes as well as microorganisms. Using biowaste materials to design hybrid nanoparticles with enhanced photocatalytic and antimicrobial features would uphold the principles of the circular bioeconomy. Here, two unexpensive semiconductors-namely titanium dioxide (TiO2) and zinc oxide (ZnO) - were synthetized through solvothermal synthesis and combined with humic substances deriving from agrifood biomass. The preparation led to hybrid nanoparticles exhibiting enhanced ROS-generating properties for simultaneous applications as antimicrobial agents against different bacterial and fungal strains and as photoactive catalysts to degrade polylactic acid (PLA) microplastics under UVA and solar irradiation. In comparison to bare nanoparticles, hybrid nanoparticles demonstrated higher antibacterial and antimycotic capabilities toward various pathogenic microorganisms as well as advanced photocatalytic activity in the degradation of PLA with a carbonyl index reduction in the range of 15–23%, thus confirming a noteworthy ability in microplastics photodegradation under UVA and solar irradiation.

UV Light Degradation of Polylactic Acid Kickstarts Enzymatic Hydrolysis.

Polylactic acid (PLA) and bioplastics alike have a designed degradability to avoid the environmental buildup that petroplastics have created. Yet, this designed biotic-degradation has typically been characterized in ideal conditions. This study seeks to relate the abiotic to the biotic degradation of PLA to accurately represent the degradation pathways bioplastics will encounter, supposing their improper disposal in the environment. Enzymatic hydrolysis was used to study the biodegradation of PLA with varying stages of photoaging. Utilizing a fluorescent tag to follow enzyme hydrolysis, it was determined that increasing the amount of irradiation yielded greater amounts of total enzymatic hydrolysis by proteinase K after 8 h of enzyme incubation. While photoaging of the polymers causes minimal changes in chemistry and increasing amounts of crystallinity, the trends in biotic degradation appear to primarily be driven by photoinduced reduction in molecular weight. The relationship between photoaging and enzyme hydrolysis appears to be independent of enzyme type, though commercial product degradation may be impacted by the presence of additives. Overall, this work reveals the importance of characterizing biodegradation with relevant samples that ultimately can inform optimization of production and disposal.