Sustainable struggling: decoding microplastic released from bioplastics-a critical review.

This comprehensive review delves into the complex issue of plastic pollution, focusing on the emergence of biodegradable plastics (BDPs) as a potential alternative to traditional plastics. While BDPs seem promising, recent findings reveal that a large number of BDPs do not fully degrade in certain natural conditions, and they often break down into microplastics (MPs) even faster than conventional plastics. Surprisingly, research suggests that biodegradable microplastics (BDMPs) could have more significant and long-lasting effects than petroleum-based MPs in certain environments. Thus, it is crucial to carefully assess the ecological consequences of BDPs before widely adopting them commercially. This review thoroughly examines the formation of MPs from prominent BDPs, their impacts on the environment, and adsorption capacities. Additionally, it explores how BDMPs affect different species, such as plants and animals within a particular ecosystem. Overall, these discussions highlight potential ecological threats posed by BDMPs and emphasize the need for further scientific investigation before considering BDPs as a perfect solution to plastic pollution.

Effect of conventional and biodegradable microplastics on earthworms during vermicomposting process.

The potential effect of microplastics is an increasingly growing environmental issue. However, very little is known regarding the impact of microplastics on the vermicomposting process. The present study explored the effect of non-biodegradable (low density polyethylene; LDPE) and biodegradable (polybutylene succinate-co-adipate; PBSA) microplastics on earthworm Eisenia fetida during vermicomposting of cow dung. For this, earthworms were exposed to different concentrations (0, 0.5, 1 and 2%) of LDPE and PBSA of 2 mm size. The cow dung supported the growth and hatchlings of earthworms, and the toxicity effect of both LDPE and PBSA microplastics on Eisenia fetida was analyzed. Microplastics decreased the body weight of earthworms and there was no impact on hatchlings. The body weight of earthworm decreased from 0 to 60th day by 18.18% in 0.5% of LDPE treatment, 5.42% in 1% of LDPE, 20.58% in 2% of LDPE, 19.99% in 0.5% of PBSA, 15.09% in 1% of PBSA and 16.36% in 2% of PBSA. The physico-chemical parameters [pH (8.55-8.66), electrical conductivity (0.93-1.02 (S/m), organic matter (77.6-75.8%), total nitrogen (3.95-4.25 mg/kg) and total phosphorus (1.16-1.22 mg/kg)] do not show much significant changes with varying microplastics concentrations. Results of SEM and FTIR-ATR analysis observed the surface damage of earthworms, morphological and biochemical changes at higher concentrations of both LDPE and PBSA. The findings of the present study contribute to a better understanding of microplastics in vermicomposting system.

Ecotoxicity assessment of additives in commercial biodegradable plastic products: Implications for sustainability and environmental risk.

Biodegradable plastics have gained popularity as environmentally friendly alternatives to conventional petroleum-based plastics, which face recycling and degradation challenges. Although the biodegradability of these plastics has been established, research on their ecotoxicity remains limited. Biodegradable plastics may still contain conventional additives, including toxic and non-degradable substances, to maintain their functionality during production and processing. Despite degrading the polymer matrix, these additives can persist in the environment and potentially harm ecosystems and humans. Therefore, this study aimed to assess the potential ecotoxicity of biodegradable plastics by analyzing the phthalate esters (PAEs) leaching out from biodegradable plastics through soil leachate. Sixteen commercial biodegradable plastic products were qualitatively and quantitatively analyzed using gas chromatography-mass spectrometry to determine the types and amounts of PAE used in the products and evaluate their ecotoxicity. Among the various PAEs analyzed, non-regulated dioctyl isophthalate (DOIP) was the most frequently detected (ranging from 40 to 212 µg g-1). Although the DOIP is considered one of PAE alternatives, the detected amount of it revealed evident ecotoxicity, especially in the aquatic environment. Other additives, including antioxidants, lubricants, surfactants, slip agents, and adhesives, were also qualitatively detected in commercial products. This is the first study to quantify the amounts of PAEs leached from biodegradable plastics through water mimicking PAE leaching out from biodegradable plastics to soil leachate when landfilled and evaluate their potential ecotoxicity. Despite their potential toxicity, commercial biodegradable plastics are currently marketed and promoted as environmentally friendly materials, which could lead to indiscriminate public consumption. Therefore, in addition to improving biodegradable plastics, developing eco-friendly additives is significant. Future studies should investigate the leaching kinetics in soil leachate over time and toxicity of biodegradable plastics after landfill disposal.

Biodegradable microplastics pose greater risks than conventional microplastics to soil properties, microbial community and plant growth, especially under flooded conditions.

Biodegradable plastics (bio-plastics) are often viewed as viable option for mitigating plastic pollution. Nevertheless, the information regarding the potential risks of microplastics (MPs) released from bio-plastics in soil, particularly in flooded soils, is lacking. Here, our objective was to investigate the effect of polylactic acid MPs (PLA-MPs) and polyethylene MPs (PE-MPs) on soil properties, microbial community and plant growth under both non-flooded and flooded conditions. Our results demonstrated that PLA-MPs dramatically increased soil labile carbon (C) content and altered its composition and chemodiversity. The enrichment of labile C stimulated microbial N immobilization, resulting in a depletion of soil mineral nitrogen (N). This specialized environment created by PLA-MPs further filtered out specific microbial species, resulting in a low diversity and simplified microbial community. PLA-MPs caused an increase in denitrifiers (Noviherbaspirillum and Clostridium sensu stricto) and a decrease in nitrifiers (Nitrospira, MND1, and Ellin6067), potentially exacerbating the mineral N deficiency. The mineral N deficit caused by PLA-MPs inhibited wheatgrass growth. Conversely, PE-MPs had less effect on soil ecosystems, including soil properties, microbial community and wheatgrass growth. Overall, our study emphasizes that PLA-MPs cause more adverse effect on the ecosystem than PE-MPs in the short term, and that flooded conditions exacerbate and prolong these adverse effects. These results offer valuable insights for evaluating the potential threats of bio-MPs in both uplands and wetlands.

Biodegradable plastic formulated from chitosan of Aristeus antennatus shells with castor oil as a plasticizer agent and starch as a filling substrate.

Biodegradable plastics are those subjected easily to a degradation process, in which they can be decomposed after disposal in the environment through microbial activity. 30 bioplastic film formulations based only on chitosan film were used in the current investigation as a positive control together with chitosan film recovered from chitin-waste of locally obtained Aristeus antennatus. Additionally, castor oil was used as a plasticizer. While the yield of chitosan was 18% with 7.65% moisture content and 32.27% ash in the shells, the isolated chitin had a degree of deacetylation (DD) of 86%. The synthesized bioplastic films were characterized via numerous criteria. Firstly, the swelling capacity of these biofilms recorded relatively high percentages compared to polypropylene as synthetic plastic. Noticeably, the FTIR profiles, besides DSC, TGA, and XRD, confirmed the acceptable characteristics of these biofilms. In addition, their SEM illustrated the homogeneity and continuity with a few straps of the chitosan film and showed the homogeneous mixes of chitosan and castor oil with 5 and 20%. Moreover, data detected the antibacterial activity of different bioplastic formulas against some common bacterial pathogens (Enterococcus feacalis, Kelbsiella pnumina, Bacillus subtilis, and Pseudomonas aeruginosa). Amazingly, our bioplastic films have conducted potent antimicrobial activities. So, they may be promising in such a direction. Further, the biodegradability efficacy of bioplastic films formed was proved in numerous environments for several weeks of incubation. However, all bioplastic films decreased in their weights and changed in their colors, while polypropylene, was very constant all the time. The current findings suggest that our biofilms may be promising for many applications, especially in the field of food package protecting the food, and preventing microbial contamination, consequently, it may help in extending the shelf life of products.

Can bioplastics always offer a truly sustainable alternative to fossil-based plastics?

Bioplastics, comprised of bio-based and/or biodegradable polymers, have the potential to play a crucial role in the transition towards a sustainable circular economy. The use of biodegradable polymers not only leads to reduced greenhouse gas emissions but also might address the problem of plastic waste persisting in the environment, especially when removal is challenging. Nevertheless, biodegradable plastics should not be considered as substitutes for proper waste management practices, given that their biodegradability strongly depends on environmental conditions. Among the challenges hindering the sustainable implementation of bioplastics in the market, the development of effective downstream recycling routes is imperative, given the increasing production volumes of these materials. Here, we discuss about the most advisable end-of-life scenarios for bioplastics. Various recycling strategies, including mechanical, chemical or biological (both enzymatic and microbial) approaches, should be considered. Employing enzymes as biocatalysts emerges as a more selective and environmentally friendly alternative to chemical recycling, allowing the production of new bioplastics and added value and high-quality products. Other pending concerns for industrial implementation of bioplastics include misinformation among end users, the lack of a standardised bioplastic labelling, unclear life cycle assessment guidelines and the need for higher financial investments. Although further research and development efforts are essential to foster the sustainable and widespread application of bioplastics, significant strides have already been made in this direction.

Assessing microbial plastic degradation requires robust methods.

Plastics are versatile materials that have the potential to propel humanity towards circularity and ultimate societal sustainability. However, the escalating concern surrounding plastic pollution has garnered significant attention, leading to widespread negative perceptions of these materials. Here, we question the role microbes may play in plastic pollution bioremediation by (i) defining polymer biodegradability (i.e., recalcitrant, hydrolysable and biodegradable polymers) and (ii) reviewing best practices for evaluating microbial biodegradation of plastics. We establish recommendations to facilitate the implementation of rigorous methodologies in future studies on plastic biodegradation, aiming to push this field towards the use of isotopic labelling to confirm plastic biodegradation and further determine the molecular mechanisms involved.

Discrepant soil microbial community and C cycling function responses to conventional and biodegradable microplastics.

Biodegradable microplastics (MPs) are promising alternatives to conventional MPs and are of high global concern. However, their discrepant effects on soil microorganisms and functions are poorly understood. In this study, polyethylene (PE) and polylactic acid (PLA) MPs were selected to investigate the different effects on soil microbiome and C-cycling genes using high-throughput sequencing and real-time quantitative PCR, as well as the morphology and functional group changes of MPs, using scanning electron microscopy and Fourier transform infrared spectroscopy, and the driving factors were identified. The results showed that distinct taxa with potential for MP degradation and nitrogen cycling were enriched in soils with PLA and PE, respectively. PLA, smaller size (150-180 µm), and 5% (w/w) of MPs enhanced the network complexity compared with PE, larger size (250-300 µm), and 1% (w/w) of MPs, respectively. PLA increased ß-glucosidase by up to 2.53 times, while PE (150-180 µm) reduced by 38.26-44.01% and PE (250-300 µm) increased by 19.00-22.51% at 30 days. Amylase was increased by up to 5.83 times by PLA (150-180 µm) but reduced by 40.26-62.96% by PLA (250-300 µm) and 16.11-43.92% by PE. The genes cbbL, cbhI, abfA, and Lac were enhanced by 37.16%- 1.99 times, 46.35%- 26.46 times, 8.41%- 69.04%, and 90.81%- 5.85 times by PLA except for PLA1B/5B at 30 days. These effects were associated with soil pH, NO3--N, and MP biodegradability. These findings systematically provide an understanding of the impact of biodegradable MPs on the potential for global climate change.

Gelatine Blends Modified with Polysaccharides: A Potential Alternative to Non-Degradable Plastics.

Non-degradable plastics of petrochemical origin are a contemporary problem of society. Due to the large amount of plastic waste, there are problems with their disposal or storage, where the most common types of plastic waste are disposable tableware, bags, packaging, bottles, and containers, and not all of them can be recycled. Due to growing ecological awareness, interest in the topics of biodegradable materials suitable for disposable items has begun to reduce the consumption of non-degradable plastics. An example of such materials are biodegradable biopolymers and their derivatives, which can be used to create the so-called bioplastics and biopolymer blends. In this article, gelatine blends modified with polysaccharides (e.g., agarose or carrageenan) were created and tested in order to obtain a stable biopolymer coating. Various techniques were used to characterize the resulting bioplastics, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), contact angle measurements, and surface energy characterization. The influence of thermal and microbiological degradation on the properties of the blends was also investigated. From the analysis, it can be observed that the addition of agarose increased the hardness of the mixture by 27% compared to the control sample without the addition of polysaccharides. In addition, there was an increase in the surface energy (24%), softening point (15%), and glass transition temperature (14%) compared to the control sample. The addition of starch to the gelatine matrix increased the softening point by 15% and the glass transition temperature by 6%. After aging, both compounds showed an increase in hardness of 26% and a decrease in tensile strength of 60%. This offers an opportunity as application materials in the form of biopolymer coatings, dietary supplements, skin care products, short-term and single-contact decorative elements, food, medical, floriculture, and decorative industries.

Novel enhancement of interfacial interaction and properties in biodegradable polymer composites using green chemically treated spent coffee ground microfiller.

This study investigates the potential of utilizing green chemically treated spent coffee grounds (SCGs) as micro biofiller reinforcement in Poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) biopolymer composites. The aim is to assess the impact of varying SCG concentrations (1 %, 3 %, 5 %, and 7 %) on the functional, thermal, mechanical properties and biodegradability of the resulting composites with a PHBV matrix. The samples were produced through melt compounding using a twin-screw extruder and compression molding. The findings indicate successful dispersion and distribution of SCGs microfiller into PHBV. Chemical treatment of SCG microfiller enhanced the interfacial bonding between the SCG and PHBV, evidenced by higher water contact angles of the biopolymer composites. Field Emission Scanning Electron Microscopy (FE-SEM) confirmed the successful interaction of treated SCG microfiller, contributing to enhanced mechanical characteristics. A two-way ANOVA was conducted for statistical analysis. Mass losses observed after burying the materials in natural soil indicated that the composites degraded faster than the pure PHBV polymer suggesting that both composites are biodegradable, particularly at high levels of spent coffee grounds (SCG). Despite the possibility of agglomeration at higher concentrations, SCG incorporation resulted in improved functional properties, positioning the green biopolymer composite as a promising material for sustainable packaging and diverse applications.

Biodegradable plastics in Mediterranean coastal environments feature contrasting microbial succession.

Plastic pollution of the ocean is a top environmental concern. Biodegradable plastics present a potential "solution" in combating the accumulation of plastic pollution, and their production is currently increasing. While these polymers will contribute to the future plastic marine debris budget, very little is known still about the behavior of biodegradable plastics in different natural environments. In this study, we molecularly profiled entire microbial communities on laboratory confirmed biodegradable polybutylene sebacate-co-terephthalate (PBSeT) and polyhydroxybutyrate (PHB) films, and non-biodegradable conventional low-density polyethylene (LDPE) films that were incubated in situ in three different coastal environments in the Mediterranean Sea. Samples from a pelagic, benthic, and eulittoral habitat were taken at five timepoints during an incubation period of 22 months. We assessed the presence of potential biodegrading bacterial and fungal taxa and contrasted them against previously published in situ disintegration data of these polymers. Scanning electron microscopy imaging complemented our molecular data. Putative plastic degraders occurred in all environments, but there was no obvious "core" of shared plastic-specific microbes. While communities varied between polymers, the habitat predominantly selected for the underlying communities. Observed disintegration patterns did not necessarily match community patterns of putative plastic degraders.

Enzyme modified biodegradable plastic preparation and performance in anaerobic co-digestion with food waste.

A modified biodegradable plastic (PLA/PBAT) was developed by through covalent bonding with proteinase K, porcine pancreatic lipase, or amylase, and was then investigated in anaerobic co-digestion mixed with food waste. Fluorescence microscope validated that enzymes could remain stable in modified the plastic, even after co-digestion. The results of thermophilic anaerobic co-digestion showed that, degradation of the plastic modified with Proteinase K increased from 5.21 ± 0.63 % to 29.70 ± 1.86 % within 30 days compare to blank. Additionally, it was observed that the cumulative methane production increased from 240.9 ± 0.5 to 265.4 ± 1.8 mL/gVS, and the methane production cycle was shortened from 24 to 20 days. Interestingly, the kinetic model suggested that the modified the plastic promoted the overall hydrolysis progression of anaerobic co-digestion, possibly as a result of the enhanced activities of Bacteroidota and Thermotogota. In conclusion, under anaerobic co-digestion, the modified the plastic not only achieved effective degradation but also facilitated the co-digestion process.

The effect of additives on the biodegradation of polyhydroxyalkanoate (PHA) in marine field trials.

The persistence of conventional fossil fuel-derived plastics in marine ecosystems has raised significant environmental concerns. Biodegradable plastics are being explored as an alternative. This study investigates the biodegradation behaviour in two marine environments of melt-extruded sheets of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) bioplastic as well as blends of PHBV with a non-toxic plasticiser (triethyl citrate, TEC) and composites of PHBV with wood flour. Samples were submerged for up to 35 weeks in two subtropical marine conditions: on the sandy seabed in the sublittoral benthic zone and the sandy seabed of an open air mesocosm with pumped seawater. Rates of biodegradation, lag times and times to 95 % mass loss (T95) were determined through mass loss data and Gompertz modelling. Mechanisms of biodegradation were studied through changes in molecular weight, mechanical properties and surface features. Results reveal a rapid biodegradation rate for all PHBV samples, demonstrating a range of specific biodegradation rates relative to exposed surface area of 0.03 ± 0.01 to 0.09 ± 0.04 mg.d-1.cm-2. This rapid rate of biodegradation meant that the subtle variations in biodegradation mechanisms across different sample thicknesses and additive compositions had little effect on overall lifetimes, with the T95 for most samples being around 250-350 days, regardless of site, highlighting the robust biodegradability of PHBV in seawater. It was only the PHBV-wood flour composite that showed faster biodegradation, and that was only in the exposed ocean site. The mesocosm site was otherwise shown to be a good model for the open ocean, with very comparable biodegradation rates and changes in mechanical properties over time.

Effect of biodegradable polymers upon grazing activity of the sea urchin Paracentrotus lividus (Lmk) revealed by morphological, histological and molecular analyses.

In the last years biodegradable polymers (BPs) were largely used as real opportunity to solve plastic pollution. Otherwise, their wide use in commercial products, such as packaging sector, is causing a new pollution alarm, mainly because few data reported about their behaviour in the environment and toxicity on marine organisms. Our previous results showed that embryos of the sea urchin Paracentrotus lividus (Lmk) exposed to poly(ε-caprolactone) (PCL), poly(3-hydroxybutyrate) (PHB) and poly(lactic acid) (PLA) showed delay of their development and morphological malformations, also affecting at the molecular levels the expression of several genes involved in different functional responses. In the present work for the first time, we tested the effects of five microplastics (MPs) obtained from BPs such as PBS, poly(butylene succinate), PBSA, poly(butylene succinate-co-butylene adipate), PCL, PHB and PLA, upon grazing activity of the sea urchin revealed by: i. histological analysis seeing at the gonadic tissues; ii. morphological analysis of the deriving embryos; iii. molecular analyses on these embryos to detect variations of the gene expression of eighty-seven genes involved in stress response, detoxification, skeletogenesis, differentiation and development. All these results will help in understanding how MP accumulated inside various organs in the adult sea urchins, and more in general in marine invertebrates, could represent risks for the marine environment.

Behavioral toxicity and neurotoxic mechanisms of PLA-PBAT biodegradable microplastics in zebrafish.

Escalation of ecological concern due to biodegradable plastics has attracted the attention of many contemporary researchers. This study searched to investigate the acute and sub-chronic toxicity of polylactic acid (PLA) and polybutyleneadipate-co-terephthalate (PLA-PBAT) bio-microplastics on 3-month-old zebrafish to elucidate their potential toxic mechanisms. Acute toxicity assessments revealed 96 h-LC50 value of 12.69 mg/L for PLA-PBAT. Sub-chronic exposure of over 21 days revealed deviations in critical behavioral patterns and physiological indicators. In treated groups, weight gain and specific growth rates were significantly lower than those obtained for the control group, such that high doses induced significant reductions in total organ coefficient (p < 0.05). A positive correlation was observed between zebrafish mortality and increased doses. Detailed behavioral evaluations revealed a dose-dependent decrease in the speed and range of swimming, along with modifications in shoaling behavior, anxiety-like responses, and avoidance behaviors. Brain tissues transcriptomic analyses revealed the molecular responses underlying sub-chronic exposure to PLA-PBAT. Totally 702 DEGs and 5 KEGG pathways were significantly identified in low-dose group, with the top 2 significant pathways being ribosome pathway and cytokine-cytokine receptor interaction pathway. Totally 650 DEGs and 5 KEGG pathways were significantly identified in medium-dose group, with the top 2 significant pathways being Herpes simplex virus 1 infection pathway and complement and coagulation cascades pathway. Totally 1778 DEGs and 16 KEGG pathways were significantly identified in high-dose group, with the top 2 significant pathways being metabolism of xenobiotics by cytochrome P450 and drug metabolism - cytochrome P450 pathway. Most significantly enriched pathways are associated with immune responses. The validation of key gene in cytokine-cytokine receptor interaction pathway also confirmed its high correlation with behavioral indicators. These results indicate that PLA-PBAT is likely to cause behavioral abnormalities in zebrafish by triggering immune dysregulation in the brain.

Advances in microbial exoenzymes bioengineering for improvement of bioplastics degradation.

Plastic pollution has become a major global concern, posing numerous challenges for the environment and wildlife. Most conventional ways of plastics degradation are inefficient and cause great damage to ecosystems. The development of biodegradable plastics offers a promising solution for waste management. These plastics are designed to break down under various conditions, opening up new possibilities to mitigate the negative impact of traditional plastics. Microbes, including bacteria and fungi, play a crucial role in the degradation of bioplastics by producing and secreting extracellular enzymes, such as cutinase, lipases, and proteases. However, these microbial enzymes are sensitive to extreme environmental conditions, such as temperature and acidity, affecting their functions and stability. To address these challenges, scientists have employed protein engineering and immobilization techniques to enhance enzyme stability and predict protein structures. Strategies such as improving enzyme and substrate interaction, increasing enzyme thermostability, reinforcing the bonding between the active site of the enzyme and substrate, and refining enzyme activity are being utilized to boost enzyme immobilization and functionality. Recently, bioengineering through gene cloning and expression in potential microorganisms, has revolutionized the biodegradation of bioplastics. This review aimed to discuss the most recent protein engineering strategies for modifying bioplastic-degrading enzymes in terms of stability and functionality, including enzyme thermostability enhancement, reinforcing the substrate binding to the enzyme active site, refining with other enzymes, and improvement of enzyme surface and substrate action. Additionally, discovered bioplastic-degrading exoenzymes by metagenomics techniques were emphasized.

Unveiling the detrimental effects of polylactic acid microplastics on rice seedlings and soil health.

The environmental impact of biodegradable polylactic acid microplastics (PLA-MPs) has become a global concern, with documented effects on soil health, nutrient cycling, water retention, and crop growth. This study aimed to assess the repercussions of varying concentrations of PLA-MPs on rice, encompassing aspects such as growth, physiology, and biochemistry. Additionally, the investigation delved into the influence of PLA-MPs on soil bacterial composition and soil enzyme activities. The results illustrated that the highest levels of PLA-MPs (2.5%) impaired the photosynthesis activity of rice plants and hampered plant growth. Plants exposed to the highest concentration of PLA-MPs (2.5%) displayed a significant reduction of 51.3% and 47.7% in their root and shoot dry weights, as well as a reduction of 53% and 49% in chlorophyll a and b contents, respectively. The activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) in rice leaves increased by 3.1, 2.8, 3.5, and 5.2 folds, respectively, with the highest level of PLA-MPs (2.5%). Soil enzyme activities, such as CAT, urease, and dehydrogenase (DHA) increased by 19.2%, 10.4%, and 22.5%, respectively, in response to the highest level of PLA-MPs (2.5%) application. In addition, PLA-MPs (2.5%) resulted in a remarkable increase in the relative abundance of soil Proteobacteria, Nitrospirae, and Firmicutes by 60%, 31%, and 98.2%, respectively. These findings highlight the potential adverse effects of PLA-MPs on crops and soils. This study provides valuable insights into soil-rice interactions, environmental risks, and biodegradable plastic regulation, underscoring the need for further research.

Structural evaluation of Poly(lactic acid) degradation at standardized composting temperature of 58 degrees.

The accumulation of petroleum-based plastics on our planet is causing serious environmental pollution. Biodegradable plastics, promoted as eco-friendly solutions, hold the potential to address this issue. However, their impact on the environment and the mechanisms of their natural degradation remain inadequately understood. Furthermore, the specific conditions set forth in international standards for evaluating the biodegradability of biodegradable plastics have led to misconceptions about their real-world behavior. To properly elucidate the relationship between their degradability and structure, this study mimics the thermal effect on poly(lactic acid) (PLA) under standardized composting temperature. The higher the crystallinity of PLA, the lower the degradation rate, which suggests that crystallinity is a key factor in determining degradation. The composting temperature of 58 °C induces crystallization by having a structural effect on the polymer, which in turn reduces the degradation rate of PLA. Therefore, control over temperature and crystallization during the processing and degradation of PLA is crucial, as it not only determines the biodegradability but also enhances the utility.

Fractionated lignin as a green compatibilizer to improve the compatibility of poly (butylene adipate-co-terephthalate) /polylactic acid composites.

Blending poly (butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA) is a cost-effective strategy to obtain biodegradable plastic with complementary properties. However, the incompatibility between PBAT and PLA is a great challenge for fabricating high-performance composite films. Herein, the ethyl acetate fractionated lignin with the small glass transition temperature and low molecular weight was achieved and incorporated into the PBAT/PLA composite as a compatibilizer. The fractionated lignin can be uniformly dispersed within the PBAT/PLA matrix through a melt blending process and interact with the molecular chain of PBAT and PLA as a bonding bridge, which enhances the intermolecular interactions and reduces the interfacial tension of PBAT/PLA. By adding fractionated lignin, the tensile strength of the PBAT/PLA composite increased by 35.4 % and the yield strength increased by 37.7 %. Owing to lignin, the composite films possessed the ultraviolet shielding function and exhibited better water vapor barrier properties (1.73 ± 0.08 × 10-13 g·cm/cm2·s·Pa). This work conclusively demonstrated that fractionated lignin can be used as a green compatibilizer and a low-cost functional filler for PBAT/PLA materials, and provides guidance for the application of lignin in biodegradable plastics.

Mature compost promotes biodegradable plastic degradation and reduces greenhouse gas emission during food waste composting.

Mature compost can promote the transformation of organic matter (OM) and reduce the emission of polluting gases during composting, which provides a viable approach to reduce the environmental impacts of biodegradable plastics (BPs). This study investigated the impact of mature compost on polybutylene adipate terephthalate (PBAT) degradation, greenhouse gas (GHG) emission, and microbial community structure during composting under two treatments with mature compost (MC) and without (CK). Under MC, visible plastic rupture was advanced from day 14 to day 10, and a more pronounced rupture was observed at the end of composting. Compared with CK, the degradation rate of PBAT in MC was increased by 4.44 % during 21 days of composting. Thermobifida, Ureibacillus, and Bacillus, as indicator species under MC treatment, played an important role in PBAT decomposition. Mature compost reduced the total global warming potential (GWP) by 25.91 % via inhibiting the activity of bacteria related to the production of CH4 and N2O. Functional Annotation of Prokaryotic Taxa (FAPROTAX) further revealed that mature compost addition increased relative abundance of bacteria related to multiple carbon (C) cycle functions such as methylotrophy, hydrocarbon degradation and cellulolysis, inhibited nitrite denitrification and denitrification, thus alleviating the emission of GHGs. Overall, mature compost, as an effective additive, exhibits great potential to simultaneously mitigate BP and GHG secondary pollution in co-composting of food waste and PBAT.