Comprehensive analysis of bioplastics: life cycle assessment, waste management, biodiversity impact, and sustainable mitigation strategies.

Bioplastics are emerging as a promising alternative to traditional plastics, driven by the need for more sustainable options. This review article offers an in-depth analysis of the entire life cycle of bioplastics, from raw material cultivation to manufacturing and disposal, with a focus on environmental impacts at each stage. It emphasizes the significance of adopting sustainable agricultural practices and selecting appropriate feedstock to improve environmental outcomes. The review highlights the detrimental effects of unsustainable farming methods, such as pesticide use and deforestation, which can lead to soil erosion, water pollution, habitat destruction, and increased greenhouse gas emissions. To address these challenges, the article advocates for the use of efficient extraction techniques and renewable energy sources, prioritizing environmental considerations throughout the production process. Furthermore, the methods for reducing energy consumption, water usage, and chemical inputs during manufacturing by implementing eco-friendly technologies. It stresses the importance of developing robust disposal systems for biodegradable materials and supports recycling initiatives to minimize the need for new resources. The holistic approach to sustainability, including responsible feedstock cultivation, efficient production practices, and effective end-of-life management. It underscores the need to evaluate the potential of bioplastics to reduce plastic pollution, considering technological advancements, infrastructure development, and increased consumer awareness. Future research should focus on enhancing production sustainability, understanding long-term ecological impacts, and advancing bioplastics technology for better performance and environmental compatibility. This comprehensive analysis of bioplastics' ecological footprint highlights the urgent need for sustainable solutions in plastic production.

Novel Bioplastic Based on PVA Functionalized with Anthocyanins: Synthesis, Biochemical Properties and Food Applications.

Over the last ten years, researchers' efforts have aimed to replace the classic linear economy model with the circular economy model, favoring green chemical and industrial processes. From this point of view, biologically active molecules, coming from plants, flowers and biomass, are gaining considerable value. In this study, firstly we focus on the development of a green protocol to obtain the purification of anthocyanins from the flower of Callistemon citrinus, based on simulation and on response surface optimization methodology. After that, we utilize them to manufacture and add new properties to bioplastics belonging to class 3, based on modified polyvinyl alcohol (PVA) with increasing amounts from 0.10 to 1.00%. The new polymers are analyzed to monitor morphological changes, optical properties, mechanical properties and antioxidant and antimicrobial activities. Fourier transform infrared spectroscopy (FTIR) spectra of the new materials show the characteristic bands of the PVA alone and a modification of the band at around 1138 cm-1 and 1083 cm-1, showing an influence of the anthocyanins' addition on the sequence with crystalline and amorphous structures of the starting materials, as also shown by the results of the mechanical tests. These last showed an increase in thickening (from 29.92 µm to approx. 37 µm) and hydrophobicity with the concomitant increase in the added anthocyanins (change in wettability with water from 14° to 31°), decreasing the poor water/moisture resistance of PVA that decreases its strength and limits its application in food packaging, which makes the new materials ideal candidates for biodegradable packaging to extend the shelf-life of food. The functionalization also determines an increase in the opacity, from 2.46 to 3.42 T%/mm, the acquisition of antioxidant activity against 2,2-diphenyl-1-picrylhdrazyl and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radicals and, in the ferric reducing power assay, the antimicrobial (bactericidal) activity against different Staphylococcus aureus strains at the maximum tested concentration (1.00% of anthocyanins). On the whole, functionalization with anthocyanins results in the acquisition of new properties, making it suitable for food packaging purposes, as highlighted by a food fresh-keeping test.

Accelerated aging behavior of degradable and non-degradable microplastics via advanced oxidation and their adsorption characteristics towards tetracycline.

The increasing global utilization of biodegradable plastics due to stringent regulations on traditional plastics has caused a significant rise in microplastic (MPs) pollution in aquatic ecosystems from biodegradable products. However, the environmental behavior of biodegradable MPs remains inadequately elucidated. This study explored the aging processes of polylactic acid (PLA) and polystyrene (PS) under a heat-activated potassium persulfate (K2S2O8) system, as well as their adsorption characteristics towards tetracycline (TCs). In comparison to PS, the surface structure of PLA experienced more pronounced changes over aging, exhibiting evident pits, cracks, and fragmentation. The carbonyl index (CI) and oxygen/carbon ratio (O/C) of PS displayed exponential growth over time, whereas the values for PLA showed linear and exponential increases, respectively. The adsorption capacity of TCs by PS and PLA aged for 6 days increased from 0.312 mg‧g-1 and 0.457 mg‧g-1for original PS and PLA, respectively, to 0.372 mg‧g-1 and 0.649 mg‧g-1. Meanwhile, the adsorption rate (k2 values) for TCs decreased by 42.03 % for PS and 79.64 % for PLA compared to their initial values. The findings indicated that biodegradable PLA-MPs may exhibit higher tetracycline carrying capacities than PS, potentially increasing environmental and organismal risks, particularly in view of aging effects.

Polyethylene and related hydrocarbon polymers ("plastics") are not biodegradable.

Research on the biodegradation of polyethylene (PE), polystyrene (PS) and related polymers has become popular and the number of publications on this topic is rapidly increasing. However, there is no convincing evidence that the frequently claimed biodegradability of these so-called "plastics" really exists. Rather, a diffuse definition of the term "biodegradability" has led to the publication of reports showing either marginal weight losses of hydrocarbon polymers by the action of isolated bacterial strains or mechanical disintegration and polymer surface modification in case of hydrocarbon polymer-consuming insect larvae. Most of the data can be alternatively explained by the utilization of polymer impurities/additives, by the utilization of low molecular weight oligomers, and/or by physical fragmentation and subsequent loss of small fragments. Evidence for a (partial) biotic and/or abiotic oxidation of the amorphous polymer fraction and of surface-exposed hydrocarbon side chains is not sufficient to claim that PE is biodegradable. To the best of my knowledge, no report has been so far published in which substantial biodegradation and mineralization of PE or related (long chain length) hydrocarbon polymers to carbon dioxide has been convincingly demonstrated by the determination of the fate of carbon atoms in isotope-labeled polymers. It is disappointing that publications with a critical view on biodegradation of hydrocarbon polymers are not cited in most of these reports. The possibility should be considered that the rapidly expanding research field of hydrocarbon polymer biodegradation is chasing rainbows.

Effects of starch filling on physicochemical properties, functional activities, and release characteristics of PBAT-based biodegradable active films loaded with tea polyphenols.

In this work, the modification of poly(butylene adipate-co-terephthalate) (PBAT) was combined with the development of active packaging films. PBAT, starch, plasticizer, and tea polyphenols (TP) were compounded and extrusion-blown into thermoplastic starch (TPS)/PBAT-TP active films. Effects of TPS contents on physicochemical properties, functional activities, biodegradability, and release kinetics of PBAT-based active films were explored. Starch interacted strongly with TP through hydrogen bonding and induced the formation of heterogeneous structures in the films. With the increase in TPS contents, surface hydrophilicity and water vapor permeability of the films increased, while mechanical properties decreased. Blending starch with PBAT greatly accelerated degradation behavior of the films, and the T30P70-TP film achieved complete degradation after 180 days. As TPS contents increased, swelling degree of the films increased and TP release were improved accordingly, resulting in significantly enhanced antioxidant and antimicrobial activities. This work demonstrated that filling starch into PBAT-based active films could achieve different antioxidant and antimicrobial activities of the films by regulating film swelling and release behavior.

Bioactive chitosan films: Integrating antibacterial, antioxidant, and antifungal properties in food packaging.

In this work, chitosan was combined with bio-vanillin (BV) and kaolin clay (KC) to create a novel antifungal and biodegradable food packaging film. The chitosan/KC/BV film exhibited an antioxidant capacity of 80 % as measured by DPPH assay, which was significantly higher than that of the chitosan film which has 55.6 %). The film also demonstrated strong antimicrobial activity with a reduction of 90 % in the growth of E. coli and S. aureus compared to the control. Additionally, the chitosan/KC/BV film showed a 75 % reduction in fungal growth compared to chitosan film. Furthermore, the water vapor permeability of the chitosan film was reduced as 5.38 with the addition of KC/BV. The degradation study revealed that the chitosan/KC film degraded by 88 % within 20 days under composting conditions. Additionally, fresh-cut apple slices were used to examine the effectiveness of chitosan/KC/BV film as a packaging material. The fruit's weight loss and browning index showed satisfactory food preservation. Our research suggests that the chitosan/KC/BV film has great potential for use in the food sector due to its strong antioxidant, antimicrobial, and biodegradable properties.

Ionized copolyesters with pH-responsive degradability: Accelerated degradation in specific environments.

The development of environmentally responsive biodegradable polymers is a promising solution for balancing the stability and degradability of biodegradable plastics. In this study, a commercial biodegradable polyester, poly(butylene adipate-co-butylene terephthalate) (PBAT), was used as the substrate and was synthetically modified with a small amount of anionic sodium 1-3-isophthalate-5-sulfonate (SIPA) to obtain the ionized random poly(butylene adipate-co-butylene terephthalate-co-butylene 5-sodiosulfoisophthalate) (PBATS). The introduction of the sodium sulfonate ionic group enhanced the mechanical and heat-resistant properties of the material, while significantly improving the hydrophilicity and water absorption of the copolyesters of PBATSs and endowing them with special pH-responsive degradation properties. Compared with PBAT, PBATS copolyesters could accelerate degradation in acidic or alkaline buffer solutions and natural seawater, while degradation was inhibited in neutral buffer solutions at pH 7.2. Degradation experiments in simulated gastric, intestinal, and body fluids revealed that the copolyester showed specific and rapid degradation in acidic gastric fluids. This environmentally-responsive degradable material greatly expands the special applications of biodegradable polyesters in the fields of environmental remediation and medical applications.

Enhancing biodegradation efficiency of PLA/PBAT-ST20 bioplastic using thermophilic bacteria co-culture system: New insight from structural characterization, enzyme activity, and metabolic pathways.

The rising utilization of PLA/PBAT-ST20 presents potential ecological risks stemming from its casual disposal and incomplete degradation. To solve this problem, this study investigated the degradation capabilities of PLA/PBAT-ST20 by a co-culture system comprising two thermophilic bacteria, Pseudomonas G1 and Kocuria G2, selected and identified from the thermophilic phase of compost. Structural characterization results revealed that the strains colonized the PLA/PBAT-ST20's surface, causing holes and cracks, with an increase in the carbonyl index (CI) and polydispersity index (PDI), indicating oxidative degradation. Enzyme activity results demonstrated that the co-culture system significantly enhanced the secretion and activity of proteases and lipases, promoting the breakdown of ester bonds. LC-QTOF-MS results showed that various intermediate products were obtained after degradation, ultimately participating in the TCA cycle (ko00020), further completely mineralized. Additionally, after 15-day compost, the co-culture system achieved a degradation rate of 72.14 ± 2.1 wt% for PBAT/PLA-ST20 films, with a decrease in the abundance of plastic fragments of all sizes, demonstrating efficient degradation of PLA/PBAT-ST20 films. This study highlights the potential of thermophilic bacteria to address plastic pollution through biodegradation and emphasizes that the co-culture system could serve as an ideal solution for the remediation of PLA/PBAT plastics.

Effects of silane hydrolysis time on the physicochemical properties of bioplastics based on starch and epoxidized soybean oil.

This work investigated the effects of 3-aminopropyl triethoxy silane (APTES) hydrolysis time on the physicochemical properties of the resulting starch/epoxidized soybean oil (ESO) bioplastics comprehensively. FTIR analysis confirmed that APTES hydrolyzed for 4 h had the best modification effect on starch. The results of XRD and TGA demonstrated the successful silylation of starch by APTES despite hydrolysis time. Silylation treatment reduced the thermal stability of starch slightly, but enhanced the thermal stability of the resultant bioplastics, revealing better interaction between silylated starch and ESO. The interfacial adhesion of starch and ESO in the bioplastics was obviously enhanced when APTES was hydrolyzed for 2-24 h. The bioplastics with APTES hydrolyzed for 2-4 h showed more desirable tensile properties as the silane hydrolysis was complete and self-condensation of hydrolyzed silanes was avoided. The bioplastics containing silylated starch still showed superior opacity and biodegradability.

Conversion of Bamboo into Strong, Waterproof, and Biodegradable Thermosetting Plastic through Cell Wall Structure Directed Manipulation.

Reckoning with the global environmental challenge of plastic pollution, particularly in terms of recycling and biodegradation of thermosetting plastics, sustainable alternatives are imperative. The rapidly growing and eco-friendly material bamboo has great potential as a sustainable resource; however, it lacks the inherent self-bonding and plasticity characteristics found in plastics. This study presents a feasible approach to enhance the plasticity of bamboo by selectively removing part of its lignin and disrupting the crystalline structure of cellulose. Concurrently, this process selectively transforms hydroxyl groups into highly reactive dialdehyde groups to increase the reactivity of bamboo. The resulting activated bamboo units undergo a hot-pressing process to transform them into a type of thermosetting plastic (ABTP). The ABTP is highly moldable, and its color can be precisely regulated by adjusting the lignin content. Additionally, it exhibits exceptional solvent and water resistance, along with notable mechanical properties, including a tensile strength of 50 MPa, flexural strength of 80 MPa, flexural modulus of 5 GPa, and Shore D hardness approaching 90. Furthermore, the bamboo-derived plastic exhibits exceptional reusability and biodegradability, presenting feasible and environmentally friendly alternatives to conventional plastics while harnessing the sustainable development potential of bamboo.

Adsorption behavior of heavy metals onto microplastics derived from conventional and biodegradable commercial plastic products.

This study extensively explored the adsorption behavior of heavy metals (Pb+2, Ni+2, Cu+2, Zn+2, and Cd+2) onto microplastics (MPs). The particle sizes of MPs ranged from 0.149 to 0.25 mm. The microplastics were generated from commercial products manufactured from both conventional (polyethylene (PE) bottle, polystyrene (PS) spoon, and polyethylene terephthalate (PET) egg carton) and biodegradable (polylactic acid (PLA) spoon, and polylactic acid (PLA) egg carton) plastics. The study also considered the influence of solution pH on the adsorption capacity of heavy metals. Regarding the adsorption potential for Cu+2, the ranking was as follows: PLA-egg (1408 µg·g-1) > PLA-spoon (735 µg·g-1) > PE-bottle (315 µg·g-1) > PET-egg (283 µg·g-1) > PS-spoon (237 µg·g-1). PLA MPs showed the highest adsorption capacity due to the lower thermal stability and higher presence of surface oxygen functional groups. Moreover, the adsorption capacities of the five metals onto PLA-spoon and PLA-egg decreased in the following order: Pb (1785 µg·g-1) > Zn (1267 µg·g-1) > Cd (748 µg·g-1) > Cu (735 µg·g-1) > Ni (722 µg·g-1), and Pb (1520 µg·g-1) > Ni (1412 µg·g-1) > Cu (1408 µg·g-1) > Zn (1118 µg·g-1) > Cd (423 µg·g-1), respectively. The SEM-EDS, FTIR and XPS results demonstrated that surface oxygen-containing functional groups play an important role during the adsorption process. This study extended its analysis to quantify the metal content of the post-adsorption MPs, revealing uneven adsorption of heavy metals onto the MPs. This implies that the diversity of commercial plastic products may result in significant variations in their ability to adsorb heavy metals, underscoring the importance of effectively managing discarded commercial plastic products.

The synergistic effect of polyphenols and polypeptides for plant-based bioplastic film - Enhanced UV resistance, antioxidant and antibacterial performance.

The exceptional biodegradability and active biological functions of bio-based packaging materials have attracted increasing interest. In this study, a bioplastic film was developed by introducing simultaneously polyphenols (tea polyphenols, TPs) and peptides (nisin) into a soy protein isolate/sodium alginate (SPI/SA) based film-forming matrix. The research results revealed that the dynamic coordinated interaction between TPs and nisin enhanced mechanical properties, UV-resistance, and thermal stability of bioplastic films. Furthermore, the bioplastic film exhibited antibacterial activity and antioxidant properties. Significantly, biofilm growth of Staphylococcus aureus treated with TPs-5/Nisin-5 bioplastic film was inhibited by 91.12% compared to the blank group. The shelf life of beef with TPs-5/Nisin-5 bioplastic film was prolonged by 2 days because of the synergistic effect of TPs and nisin. Additionally, the bioplastic film biodegraded in the natural environment about 21 days. This environmentally friendly regeneration strategy and the integration of advantageous functions provided ideas for the development of active food packaging.

Polyphenolic truxillic acid crosslinked sodium alginate film with notable antimicrobial and biodegradable properties for food packaging.

This work demonstrated an innovative antimicrobial and biodegradable food packaging film CBDA-10-SA which was prepared by crosslinking a natural polyphenolic truxillic acid (cyclobutane-dicarboxylic acid, CBDA-10) and sodium alginate (SA). The CBDA-10-SA film exhibited improved tensile strength (148 MPa) and UV shielding capabilities. The maximum thermal decomposition temperature was achieved of 249 °C. Compared to SA film, CBDA-10-SA showed increased antibacterial activities. In food packaging test, the CBDA-10-SA inhibited the rapid growth of potential of hydrogen (pH) value, slowed down the weight loss, reduced total plate count (TPC) value of pork, and delayed the spoilage process of pork. Notably, CBDA-10-SA displayed remarkable degradability in soil, with 60 % degrading in four weeks. In this study, CBDA-10-SA showed enhanced physicochemical and mechanical properties compared to traditional SA film. Those improvements make it anticipated to be used in not only food packaging but also mechanical, pharmaceutical, and agricultural fields.

From raw microalgae to bioplastics: Conversion of Chlorella vulgaris starch granules into thermoplastic starch.

Microalgae are emerging as a promising feedstock for bioplastics, with Chlorella vulgaris yielding significant amounts of starch. This polysaccharide is convertible into thermoplastic starch (TPS), a biodegradable plastic of industrial relevance. In this study, we developed a pilot-scale protocol for extracting and purifying starch from 430 g (dry weight - DW) of starch-enriched Chlorella vulgaris biomass. More than 200 gDW of starch were recovered, with an extraction yield and starch purity degree reaching 98 and 87 %, respectively. We have characterized this extracted starch and processed it into TPS using twin-screw extrusion and injection molding. Microalgal starch showed similar properties to those of native plant starch, but with smaller granules. We compared the mechanical properties of microalgal TPS with two controls, namely a commercial TPS and a TPS prepared from commercial potato starch granules. TPS prepared from microalgal starch showed a softer and more ductile behavior compared to the reference materials. This study demonstrates the feasibility of recovering high-purity microalgal starch at pilot scale with high yields, and highlights the potential of microalgal starch for the production of TPS using industrially relevant processes.

Converting fruit peels into biodegradable, recyclable and antimicrobial eco-friendly bioplastics for perishable fruit preservation.

The development of biodegradable antimicrobial bioplastics for food packaging holds great promise for solving the pollution and safety problems caused by petrochemical plastics and spoiled food. Herein, a natural active-bioplastic synthesized from citrus peel biomass is presented for perishable fruit preservation. These plastics are characterized by the nanoscale entanglement and recombinant hydrogen bonding between the endogenous pectin, polyphenols and cellulose micro/nanofibrils. They have attractive flexibility, tensile strength, gas barrier properties and antimicrobial activities, and can effectively extend the shelf life of perishable fruits such as banana and mango when used as food packaging. Cytotoxicity, degradability tests and life-cycle assessment show that these plastics had excellent nontoxicity and can be safely degraded or easily recycled. This work demonstrates a sustainable strategy for converting peel waste into eco-friendly bioplastics, providing a unique and novel insight into radically reducing the pollution and life-health threats posed by petrochemical plastics and spoiled food.

Exploring the advantages and limitations of degradation for various biodegradable micro-bioplastic in aquatic environments.

Biodegradable plastics are being the substitute for synthetic plastics and widely been used in order to combat plastic pollution. Yet not all biodegradable plastics are degradable especially when it does not meet its favourable conditions, and also when it comes to aquatic environments. Therefore, this review is intended to highlight the types of various biodegradable plastic synthesized and commercialised and identify the limitations and advantages of these micro-bioplastics or residual bioplastic upon degradation in various aquatic environments. This review paper highlights on biodegradable plastic, degradation of biodegradable plastic in aquatic environments, application of biodegradable plastic, polylactic acid (PLA), Polyhydroxyalkanoates (PHA), Polysaccharide derivatives, Poly (amino acid), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBA/T), limitations and advantages of biodegradable plastic degradation in aquatic environment. There is no limit on the period for literature search as this field is continuously being studied and there is no wide range of studies. Biodegradable plastic that is commercially available has its own advantages and limitations respectively upon degradation in both freshwater and marine environments. There is a growing demand for bioplastic as an alternative to synthetic plastic which causes plastic waste pollution. Thus, it is crucial to understand the biodegradation of biodegradable plastic in depth especially in aquatic environments. Moreover, there are also very few studies investigating the degradation and migration of micro-bioplastics in aquatic environments.

Selective recovery of pyrolyzates of biodegradable (PLA, PHBH) and common plastics (HDPE, PP, PS) during co-pyrolysis under slow heating.

Pyrolytic synergistic interactions, in which the production of pyrolyzates is enhanced or inhibited, commonly occur during the co-pyrolysis of different polymeric materials, such as plastics and biomass. Although these interactions can increase the yield of desired pyrolysis products under controlled degradation conditions, the desired compounds must be separated from complex pyrolyzates and further purified. To balance these dual effects, this study was aimed at examining pyrolytic synergistic interactions during slow heating co-pyrolysis of biodegradable plastics including polylactic acid (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexaoate) (PHBH) and petroleum-based plastics including high-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS). Comprehensive investigations based on thermogravimetric analysis, pyrolysis-gas chromatography/mass spectrometry, and evolved gas analysis-mass spectrometry revealed that PLA and PHBH decompose at lower temperatures (273-378 °C) than HDPE, PP, and PS (386-499 °C), with each polymer undergoing independent decomposition without any pyrolytic interactions. Thus, the independent pyrolysis of biodegradable plastics, such as PLA and PHBH, with common plastics, such as HDPE, PP, and PS, can theoretically be realized through temperature control, enabling the selective recovery of their pyrolyzates in different temperature ranges. Thus, pyrolytic approaches can facilitate the treatment of mixed biodegradable and common plastics.

PBAT is biodegradable but what about the toxicity of its biodegradation products?

CONTEXT: Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable plastic. It was introduced to the plastics market in 1998 and since then has been widely used around the world. The main idea of this research is to perform quantum chemical calculations to study the potential toxicity of PBAT and its degradation products. We analyzed the electron transfer capacity to determine its potential toxicity. We found that biodegradable products formed with benzene rings are as good electron acceptors as PBAT and OOH•. Our results indicate that the biodegradation products are potentially as toxic as PBAT. This might explain why biodegradation products alter the photosynthetic system of plants and inhibit their growth. From this and other previous investigations, we can think that biodegradable plastics could represent a potential environmental risk. METHODS: All DFT computations were performed using the Gaussian16 at M062x/6-311 + g(2d,p) level of theory without symmetry constraints. Electro-donating (ω-) and electro-accepting (ω +) powers were used as response functions.

Water-dependent effects of biodegradable microplastics on arsenic fractionation in soil: Insights from enzyme degradation and synchrotron-based X-ray analysis.

The abundance of biodegradable microplastics (BMPs) is increasing in soil due to the widespread use of biodegradable plastics. However, the influence of BMPs on soil metal biogeochemistry, especially arsenic (As), under different water regimes is still unclear. In this study, we investigated the effects of two types of BMPs (PLA-MPs and PBAT-MPs) on As fractionation in two types of soils (black soil and fluvo-aquic soil) under three water regimes including drying (Dry), flooding (FL), and alternate wetting and drying (AWD). The results show that BMPs had limited indirect effects on As fractionation by altering soil properties, but had direct effects by adsorbing and releasing As during their degradation. Enzyme degradation experiments show that the degradation of PLA-MPs led to an increased desorption of 4.76 % for As(III) and 15.74 % for As(V). Synchrotron-based X-ray fluorescence (µ-XRF) combined with micro-X-ray absorption near edge structure (µ-XANES) analysis show that under Dry and AWD conditions, As on the BMPs primarily bind with Fe hydrated oxides in the form of As(V). Conversely, 71.57 % of As on PBAT-MP under FL conditions is in the form of As(III) and is primarily directly adsorbed onto its surface. This study highlights the role of BMPs in soil metal biogeochemistry.

Biodegradable Microplastic-Driven Change in Soil pH Affects Soybean Rhizosphere Microbial N Transformation Processes.

The potential impacts of biodegradable and nonbiodegradable microplastics (MPs) on rhizosphere microbial nitrogen (N) transformation processes remain ambiguous. Here, we systematically investigated how biodegradable (polybutylene succinate, PBS) MPs and nonbiodegradable (polyethylene, PE) MPs affect microbial N processes by determining rhizosphere soil indicators of typical Glycine max (soybean)-soil (i.e., red and brown soils) systems. Our results show that MPs altered soil pH and dissolved organic carbon in MP/soil type-dependent manners. Notably, soybean growth displayed greater sensitivity to 1% (w/w) PBS MP exposure in red soil than that in brown soil since 1% PBS acidified the red soil and impeded nutrient uptake by plants. In the rhizosphere, 1% PBS negatively impacted microbial community composition and diversity, weakened microbial N processes (mainly denitrification and ammonification), and disrupted rhizosphere metabolism. Overall, it is suggested that biodegradable MPs, compared to nonbiodegradable MPs, can more significantly influence the ecological function of the plant-soil system.