Biodegradable Microplastics Research Articles

Impacts and mechanism of biodegradable microplastics on lake sediment properties, bacterial dynamics, and greenhouse gasses emissions

The accumulation of microplastics (MPs) in freshwater ecosystems plays a vital role in greenhouse gases (GHGs) emissions from lake sediment by altering sediment properties and microbial communities. Thus, a short-term microcosm experiment was performed to explore the effect of conventional polyethylene (PE) and biodegradable Poly (butylene-adipate-co-terephtalate) (PBAT) MPs on carbon dioxide (CO2) and methane (CH4) emissions from lake sediment and associated microbial community. The results indicated that at 1.0 % concentration, the cumulative CO2 emissions were increased by 16.8 % and the cumulative CH4 emissions were increased more than four times following the addition of biodegradable MPs compared to conventional MPs, which was due to the more dissolved organic carbon (DOC) provided by biodegradable MPs for microbial respiration. Furthermore, the cumulative CO2 and CH4 emissions significantly (p < 0.05) increased with the increasing concentrations of biodegradable MPs. Notably, the accumulation of MPs could weaken the microbial stress from requirements of energy and substrate, and increase the microbial biomass carbon (MBC) value, thus eventually improving the respiratory capacity of microbes. In addition, the biodegradable MPs significantly increased the abundance of microbes, such as Firmicutes, Myxococcota and Actinobacteriota, which were related to the function of anaerobic respiration. Overall, we concluded that the abundant DOC provided by biodegradable MPs could promote the growth of microbes in lake sediment, and they could change the structure and diversity of the microbial community, which would eventually enhance the anaerobic respiration of microbes and aggravate the GHGs emissions.

Insights into interactions of biodegradable and non-biodegradable microplastics with heavy metals.

Biodegradable microplastics (BMPs) are considered to be environmentally friendly compared to non-biodegradable plastics (NMPs). However, BMPs are likely to become toxic during their transport because of the adsorption of pollutants (e.g., heavy metals) onto them. This study investigated the uptake of six heavy metals (Cd2+, Cu2+, Cr3+, Ni2+, Pb2+, and Zn2+) by a common BMPs (polylactic acid (PLA)) and compared their adsorption characteristics to those of three types of NMPs (polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC)) for the first time. The order of heavy metal adsorption capacity among the four MPs was PE > PLA > PVC > PP. The findings suggest that BMPs contained more toxic heavy metals than some NMPs. Among the six heavy metals, Cr3+ showed considerably stronger adsorption than other heavy metals in both BMPS and NMPs. The adsorption of heavy metals on MPs can be well explained using the Langmuir isotherm model, while the adsorption kinetic curves showed the best fit to the pseudo-second-order kinetic equation. Desorption experiments revealed that BMPs released a higher percentage of heavy metals (54.6-62.6%) in the acidic environment in a shorter time (~ 6h) compared to NMPs. Overall, this study provides insights into interactions of BMPs and NMPs with heavy metals and their removal mechanisms in aquatic environment.

Insight into the effect of microplastics on the adsorption and degradation behavior of thiamethoxam in agricultural soils

Thiamethoxam and microplastics are both common pollutants in farmland soil; however, few studies have focused on the interaction between thiamethoxam and microplastics in soil. Here, a batch experiment and soil incubation experiment were performed to explore the mechanism and effects of microplastics on the adsorption and degradation behaviors of thiamethoxam in soil, respectively. First, the batch experimental results indicated that the adsorption process of thiamethoxam on the microplastic/soil mixtures and soil-only systems mainly relies on chemical interactions. All sorption processes had moderate intensities of adsorption, and the sorption process occurred on the heterogeneous surface. In addition, the particle size and dose of microplastics could both affect the adsorption behavior of thiamethoxam onto microplastics/soil systems. The sorption capacity of thiamethoxam in soil decreases as the particle size of microplastics increases, but the sorption capacity increases as the dose of microplastics increases. Second, the results of the soil incubation experiment showed that the half-lives of thiamethoxam ranged from 57.7 d to 86.6 d, from 86.6 d to 173.3 d, and 115 d in the biodegradable microplastic/soil systems, nondegradable microplastic/soil systems, soil-only systems, respectively. These results indicate that biodegradable microplastics promoted the degradation of thiamethoxam, while nondegradable microplastics delayed the degradation process of thiamethoxam in soil. Overall, microplastics could change the degradation behaviors, sorption capacity and adsorption efficiency, and then affect the mobility and persistence of thiamethoxam in the soil environment. These findings contribute to understanding the influence of microplastics on the environmental fate of pesticides in the soil environment.

Response of soybean and maize roots and soil enzyme activities to biodegradable microplastics contaminated soil

Although biodegradable plastic film is a promising alternative product for reducing polyethylene plastic pollution in agricultural soils, the effects of its residues on plant growth and soil properties remain unclear. In this study, we conducted an experiment to investigate root properties and soil enzyme activities in Poly (butylene adipate-co-terephthalate) microplastics (PBAT-MPs) contaminated soil (0 % (CK), 0.1 %, 0.2 %, 0.5 % and 1 % of dry soil weight) with soybean (Glycine max (Linn.) Merr.) and maize (Zea mays L.). The results show that PBAT-MP accumulation in soil negatively affects root growth, and alter soil enzyme activities, which may then constrain C/N cycling and potential yields. For soybean, the total root length, total root surface area and root biomass decreased by 34 %− 58 %, 34 %− 54 % and 25 %− 40 % at the harvesting stage compared to CK, respectively. The negative effects of PBAT-MPs on maize roots were greater than on soybean roots. The total root length, root surface area and root biomass of maize decreased by 37 %− 71 %, 33 %− 71 % and 24 %− 64 % at the tasseling and harvesting stage, respectively (p < 0.05). Furthermore, a statistical analysis of the data indicates that the inhibition of soybean and maize root growth by PBAT-MP accumulation was mediated by the significantly different impacts of PBAT-MP addition on C-enzyme (β-xylosidase, cellobiohydrolase, β-glucosidase) and N-enzyme activities (leucine-aminopeptidase, N-acetyl-β-glucosaminidase, alanine aminotransferase) in rhizosphere and non-rhizosphere soil, possibly due to interactions with plant-specific root exudates and microbial communities. These findings show the potential risks posed by biodegradable microplastics on the plant-soil system, and suggest that biodegradable plastic film should be applied with caution.

Dynamics of macroplastics and microplastics formed by biodegradable mulch film in an agricultural field

Conventional plastic mulch brings agronomic and economic benefits to crop production, but a large amount of plastic waste amasses when the mulch is removed from the fields after harvest. Soil-biodegradable plastic mulch (BDM) has emerged as a promising alternative to conventional plastic mulch as it can be tilled into the soil after harvest, thereby alleviating disposal problems. However, direct evidence on complete degradation of biodegradable mulch under natural conditions is still lacking. We quantified the dynamics of macro- (>5 mm) and microplastics (0.1–5 mm in size) in four years after a one-time application of mulch in a field with monoculture maize. The BDM feedstock was polybutyleneadipate-co-terephthalate (PBAT) and polylactic acid (PLA)-based, and both a clear and black BDM were tested. The BDM plastic mulch films degraded into macro- and micoplastics. Macroplastics disappeared 2.5 years after mulch incorporation. We developed a new extraction method for biodegradable microplastics using a sequential density fractionation approach with a H2O and a ZnCl2 solution. Microplastic concentrations in the soil ranged from 350 to 525 particles/kg after 2.5 years, 175 to 250 particles/kg after 3 years, and 50 to 125 particles/kg after 3.5 year following mulch incorporation. This continuous decrease of detectable plastic particle concentrations in soil suggests that BDMs fragment degrade into smaller and smaller particles, which eventually may biodegrade completely. While we cannot ascertain whether persistent and undetectable nanoplastics may form, macro- and microplastics formed from BDM seem to disappear with time.

Different effects of conventional and biodegradable microplastics on the amelioration process of cadmium-contaminated soil

With the emergence of complex soil pollution problems, the combined contamination of heavy metals and microplastics (MPs) should not be overlooked. Particularly, the safe use of farmland soils deserves more attention. Passivators were commonly used for heavy metal–contaminated soil amelioration. However, the potential impact of MPs on this process is yet to be determined. Herein, the cadmium-contaminated paddy soil was collected to evaluate the effect of MPs on soil properties and bacterial community in soil amelioration. Two types of MPs were investigated, including conventional polyethylene (PE) and biodegradable polylactic acid (PLA). Both MPs decreased the available phosphorus content and bioavailability of cadmium in a similar way, while they changed the soil pH and nitrogen species in a different manner. Additionally, the high-dose PLA treatment induced a considerable decrease in soil pH (from ~5.4 to 3.6), with potential considerable release of carbon substrates and modification of bacterial community. Furthermore, for the ameliorated soil, it has a network structure of less complexity and stabilization, which resulted in greater disparities in the microbial community under different MP treatments. Profiling predicted functions provides insights into the potential correlations among bacterial activities and soil physicochemical properties. The study demonstrated that both PE and PLA could have significant effects on the soil amelioration process and pose a threat to agroecosystems.

Accumulation and release of organic pollutants by conventional and biodegradable microplastics in the marine environment.

The issue of microplastic (MP) litter in the aquatic environment and its capability of accumulating and/or releasing pollutants has been brought to light in recent years. Biodegradable plastics have been proposed as one of the different solutions to decrease environmental input of discarded plastics; however, their ability to accumulate and release pollutants once in the marine environment has not been assessed yet. In this study, we compare the accumulation and the release of a wide range of compounds by biodegradable (polyhydroxyalkanoates (PHA) and polybutylene succinate (PBS)) and conventional (polyethylene (PE)) MPs following exposure to natural seawater for 64days. We quantified polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organophosphorus flame retardants (PFRs), phthalates, and alternative plasticizers in MPs, before and after exposure. Results indicated that PBS- and PHA-MPs accumulated the largest amount of PAHs and PFRs, respectively. Leaching of PFRs and plasticizers was observed for all polymers and was approximately twofold greater for PE- when compared to PBS- and PHA-MPs. Overall, our study suggests that biodegradable MPs may release less additives and accumulate a larger amount of contaminants from seawater compared to conventional ones: these findings may have implications on the risk assessment of biodegradable polymers for marine biota; and on potential widespread adoption of these types of plastics.

Microbe‐mediated biodegradation of microplastics from wastes

AbstractMicroplastics (MPs) with slow degradation rates carry toxins and pathogens from surroundings, accumulate and pollute the environment. They bio‐accumulate on humans and other lifeforms leading to health concerns, including inflammatory lesions, oxidative stress and increased cancer risk, thus requiring immediate remediation actions. This review summarizes, categorizes and analyses recent findings on MP source, transit and environmental toxicity and explores their microbe‐mediated breakdown. Various micro‐organisms such as fungi, bacteria, algae and protists interact with and build biofilm on MP surfaces and alter their surface morphology for their degradation. Pure strains and microbial consortia have been successfully able to degrade MPs. Extracellular enzymes are produced by these micro‐organisms that convert the complex recalcitrant polymeric structure of MP to simpler forms. Further, knowledge of factors associated with MP degradation along with the development of genetic tools enhances the rate of microbial degradation with consortium having an advantage over single bacterium‐mediated MP transformation, which has been discussed.

Distinct spatiotemporal succession of bacterial generalists and specialists in the lacustrine plastisphere.

The assembly processes of generalists and specialists and their driving mechanisms during spatiotemporal succession is a central issue in microbial ecology but a poorly researched subject in the plastisphere. We investigated the composition variation, spatiotemporal succession, and assembly processes of bacterial generalists and specialists in the plastisphere, including non-biodegradable (NBMPs) and biodegradable microplastics (BMPs). Although the composition of generalists and specialists on NBMPs differed from that of BMPs, colonization time mainly mediated the composition variation. The relative abundance of generalists and the relative contribution of species replacement were initially increased and then decreased with colonization time, while the specialists initially decreased and then increased. Besides, the richness differences also affected the composition variation of generalists and specialists in the plastisphere, and the generalists were more susceptible to richness differences than corresponding specialists. Furthermore, the assembly of generalists in the plastisphere was dominated by deterministic processes, while stochastic processes dominated the assembly of specialists. The network stability test showed that the community stability of generalists on NBMPs and BMPs was lower than corresponding specialists. Our results suggested that different ecological assembly processes shaped the spatiotemporal succession of bacterial generalists and specialists in the plastisphere, but were less influenced by polymer types.

Identification, quantification and biodegradation of microplastics from personal care products and detergents by microorganism

The pollution of microplastics from personal care products and detergents has raised significant concern. However, technologies for identification, quantification and especially for efficient degradation of microplastics remain underdeveloped. Here, we systematically study the identification and characterization of the microplastics using various analytical instrument and biodegrade the microplastics based on the metabolizing of microorganism. Raman spectroscopy and Fourier transform infrared spectrometry identify the main substance of the separated microplastics is polyolefin. Confocal laser scanning microscope images stained with Nile red reveal the shape and size of the microplastics. Energy dispersive spectrometer elemental maps suggest the C/O ratio in the microplastics. The microorganism (the bacteria we selected) grew and inhabited on or in the microplastics, and then metabolized them. The microorganism can metabolize CH2 and CC to synthesize living substance which is consist of CO. 0.22 g of microplastics on the filter paper (d = 50 mm) can be degraded completely after 33 days. This work presents a systematical way to identify and characterize the microplastics from washing and care products as well as a green and environmental-friendly protocol to biodegrade of this kind of microplastics.

Unraveling the role of natural and pyrogenic dissolved organic matter in photodegradation of biodegradable microplastics in freshwater

Biodegradable plastic is often perceived as a possible solution for microplastic (MP) pollution. Photodegradation is an important transformation pathway of biodegradable MPs in aquatic environments. However, the influence mechanisms of dissolved organic matter (DOM) from different sources on photodegradation of biodegradable MPs are poorly understood. This study explored the role of naturally and pyrogenically sourced DOM in the photodegradation of polylactic acid (PLA) MPs. The aromatics of natural DOM (NDOM) were higher than those of biochar-sourced DOM (BDOM) and showed a stronger improvement in PLA-MPs degradation, as evidenced by particle size reduction, crystallinity increase and polymerization decrease, breakage of surface morphology, and increase in oxygen-containing functional groups on MPs’ surface (O/C increase: 65.1% for NDOM; 34.9% for BDOM). Reactive oxygen species analysis showed that the excited triplet states of DOM (3DOM*) generated by NDOM produced more •OH and 1O2 than that of BDOM, accelerating PLA-MPs photodegradation. Such photodegradation processes were further enhanced through the sorption of DOM by PLA-MPs, in which non-aromatic components were preferentially sorbed, causing the enrichment of aromatics in the solution, leading to more 3DOM* formation. This study improves the understanding of the migration and transformation of biodegradable MPs with the presence of DOM.Graphical

Insights into the abiotic fragmentation of biodegradable mulches under accelerated weathering conditions

Biodegradable mulches (BMs) can be tilled into soils to mitigate disposal and environmental problems. However, the content of biodegradable microplastics (BMPs) would increase with the addition of biodegradable macroplastics (BMaPs). The fragmented particles have a strong affinity to soil pollutants, having the potential to transfer via the terrestrial food web in an agroecosystem. Based on the spectral analysis and particle size analysis, this study explored the physicochemical characteristics of weathered BMaPs and BMP-derived dissolved organic matter (DOMBMP). Ultraviolet (UV) irradiation reduced the mechanical strength of BMaPs and induced oxygenated functional groups, thus increasing surface roughness and hydrophilicity. This promoted the adsorption of aromatic compounds and heavy metals from soils to BMPs. After entering the water environment, the pH of the solution with DOMBMP decreased, whereas the concentration of dissolved organic carbon (DOC) increased. Compared with paper mulch, bioplastic mulch contributed a higher amount of DOMBMP, such as aromatic structure-containing chemicals and carboxylic acids, to the water environment but released fewer and smaller plastic particles. The findings from this study can help manage environmental risks and determine disposal strategies after the use of mulching.

Earthworms Exposed to Polyethylene and Biodegradable Microplastics in Soil: Microplastic Characterization and Microbial Community Analysis

Earthworms Exposed to Polyethylene and Biodegradable Microplastics in Soil: Microplastic Characterization and Microbial Community Analysis

Evaluating the adsorption and desorption performance of poly(butylene adipate-co-terephthalate) (PBAT) microplastics towards Cu(II): The roles of biofilms and biodegradation

The environmental risks associated with microplastics from biodegradable plastics are an emerging concern, but the roles of biofilm formation and biodegradation in the environmental behaviors of biodegradable microplastics have not been clarified. Here, we investigated the adsorption and desorption performance of Cu(II) on the poly(butylene adipate-co-terephthalate) (PBAT) microplastics and explored the roles of biofilms and biodegradation during the adsorption. The maximum adsorption quantities of Cu(II) by the pristine PBAT, the biofilm-covered PBAT, and the biodegraded PBAT were 140.547 µg·g−1, 192.197 µg·g−1, and 172.065 µg·g−1, respectively. The biodegradation increased the Cu(II) adsorption on the PBAT by 24.43%, which was due to the changes in physicochemical properties (e.g., a high surface area to volume ratio, high crystallinity, and more oxygenated groups). The surface of PBAT covered by biofilm contained oxygen- and nitrogen-containing functional groups, which could complex with more Cu(II), thus making the promoting effect of biofilm on adsorption stronger than that of biodegradation. The adsorbed Cu(II) on the surface of the biodegraded PBAT had a remarkable desorption hysteresis and was less impacted by the presence of FA, indicating that PBAT after biodegradation could transport the adsorbed heavy metals over long distances, which was not observed on the biofilm-covered PBAT. Our findings highlight the critical effects of plastic degradation on the environmental behaviors of petro-based microplastics, which helps assess the environmental fate of biodegradable microplastics in aquatic systems.

Effect of polylactic acid microplastics on soil properties, soil microbials and plant growth

Biodegradable plastic is considered one of the most promising alternatives to agricultural mulch. However, the impact of biodegradable microplastics on agricultural ecosystems is still lacking. We conducted a controlled experiment with polylactic acid microplastics (PLA MPs) to examine the effects of biodegradable plastic on soil properties, corn growth, the microbial community and hotspots of enzyme activity. The results showed that PLA MPs in soil significantly reduced the soil pH value but increased the soil C:N ratio. High levels of PLA MPs significantly reduced the biomass of plant shoots and roots as well as chlorophyll, leaf C and N and root N contents. PLA MPs increased bacterial abundance but decreased the abundance of dominant fungal taxa. As the level of PLA MPs increased, the soil bacterial community structure became more complex, while the fungal community became more singular. The results of the in situ zymogram showed that low levels of PLA MPs increased the hotspots of enzyme activity. The effect of PLA MPs on enzyme activity hotspots was regulated by a combination of soil properties and microbial diversity. Generally, the addition of PLA MPs at high concentrations will have a negative impact on soil characteristics, soil microbials and plant growth in a short period of time. Therefore, we should be aware of the potential risks of biodegradable plastic to agricultural ecosystems.

Adsorption behaviors of chlorpyrifos on UV aged microplastics

Both non-degradable and biodegradable plastics can act as vectors of diverse organic pollutants. In this study, two types of biodegradable microplastics [poly (butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA)] and one type of non-degradable microplastics [polypropylene (PP)] were selected to investigate the impacts of ultraviolet (UV) irradiation for one month on microplastics surface modification and their adsorption behaviors for chlorpyrifos (CPF). The study revealed that PBAT held the largest adsorption capacity, and PLA held the fastest adsorption rate. The UV irradiation diminished the adsorption capacities on PLA and PP but enhanced the adsorption capacities on PBAT. The adsorption capacity normalized by specific surface area revealed that specific surface area was the dominant factor for affecting the adsorption capacities on PP and PLA after UV irradiation. These findings further clarify the interaction between CPF and microplastics, and provide a theoretical basis for assessing the ecological risk of microplastics in water.

Microbes drive metabolism, community diversity, and interactions in response to microplastic-induced nutrient imbalance

The impact of conventional and biodegradable microplastics on soil nutrients (carbon and nitrogen) has been widely examined, and the alteration of nutrient conditions further influences microbial biosynthesis processes. Nonetheless, the influence of microplastic-induced nutrient imbalances on soil microorganisms (from metabolism to community interactions) is still not well understood. We hypothesized that conventional and biodegradable microplastic could alter soil nutrients and microbial processes. To fill this knowledge gap, we conducted soil microcosms with polyethylene (PE, new and aged) and polylactic acid (PLA, new and aged) microplastics to evaluate their effects on the soil enzymatic stoichiometry, co-occurrence interactions, and success patterns of soil bacterial communities. New and aged PLA induced soil N immobilization, which decreased soil mineral N by 91–141 %. The biodegradation of PLA led to a higher bioavailable C and wider bioavailable C:N ratio, which further filtered out specific microbial species. Both new and aged PLA had a higher abundance of copiotrophic members (Proteobacteria, 35–51 % in PLA, 26–34 % in CK/PE treatments) and rrn copy number. The addition of PLA resulted in a lower alpha diversity and reduced network complexity. Conversely, because of the chemically stable hydrocarbon structure of PE polymers, the new and aged PE microplastics had a minor effect on soil mineral N, bacterial community composition, and network complexity, but led to microbial C limitation. Collectively, all microplastics increased soil C-, N-, and P -acquiring enzyme activities and reduced the number of keystone species and the robustness of the co-occurrence network. The PLA treatment enhanced nitrogen fixation and ureolysis, whereas the PE treatment increased the degradation of recalcitrant carbon. Overall, the alteration of soil nutrient conditions by microplastics affected the microbial metabolism and community interactions, although the effects of PE and PLA microplastics were distinct.

The interaction effects of biodegradable microplastics and Cd on Folsomia candida soil collembolan.

In real-field soil conditions, multiple chemicals exposure may be the real scenario for soil biota. The co-occurrence of microplastics (MPs) and cadmium (Cd) is common in soils, which may pose a potential risk to soil ecosystems. Degradable microplastics are producing more MPs, and the potential effects on soil ecosystems are unknown. Therefore, a standard soil animal collembolan Folsomia candida was used to evaluate the single and interaction effects of biodegradable MPs (PLA) and Cd. The results showed that single and co-biodegradable PLA and Cd all had negative influences on the survival, reproduction, and growth of F. candida, and the effects intensified with PLA concentrations. The survival rate, reproduction rate, adult body length, and juvenile body length decreased by 20.0%, 24.2%, 22.9%, and 32.2% at MPs-100 treatment. But combined PLA and Cd alleviated the toxicity of single Cd on F. candida at lower PLA concentrations. The number of juveniles increased by 29.3%, the survival rate increased by 7.52%, the adult body length increased by 11.7%, and the juvenile body length increased by 19.0% at MPs-1 + Cd than single Cd treatment. Biochemical assays on antioxidant enzymes had the same results. Antioxidant enzymes CAT and POD were more sensitive than SOD. CAT and POD activities were induced quickly at shorter exposure periods, and MP treatment thus may be promising biomarkers on soil collembolan for soil MP exposure. PLA is degraded with time in soils; therefore, the long-term effects of co-MPs and Cd in soils are suggested to be further studied.

Degradation of Biodegradable Microplastics under Artificially Controlled Aging Conditions with UV Radiation

Due to the extensive use and improper recycling of traditional plastics, more and more policies have been issued to manage and restrict the use of traditional plastics. Therefore, Biodegradable Plastics (BPs), a substitute of traditional plastics, are widely used in daily life. However, it cannot reach the expected degradation effect in the natural environment, BPs may produce micro-plastics faster than traditional plastics called Biodegradable Microplastics (BMPs). In order to explore the degradation of BMPs, we designed a degradation experiment of BMPs under Ultraviolet (UV) radiation for 64 days. The results showed that the surface of BMPs gradually became rough with the aging time. And the both slight increase of O/C ratio and CI (carbonyl index) value of them indicated that they were oxidized under UV radiation. In addition, the crystal behaviors and the thermal stability of BMPs showed no obvious changes before and after aging. Our findings demonstrated that BMPs were less sensitive to UV radiation as compared with those of conventional plastics, giving evidence that it is necessary to increase regulation and constraints on their upstream production and subsequent disposal to achieve their environmental friendly purpose.

Distinct influence of conventional and biodegradable microplastics on microbe-driving nitrogen cycling processes in soils and plastispheres as evaluated by metagenomic analysis

Plastic mulching is one of the large contributors to microplastic (MP) accumulation in agricultural landscapes. However, the effects of conventional (PE-MPs) and biodegradable MPs (BMPs) on microbial functional and genomic information encoding nitrogen (N) cycling have yet to be addressed. Here, a soil microcosmic experiment was conducted by adding PE-MPs and BMPs to a Mollisol at dosage of 5% (w/w) followed by incubation for 90 days. The soils and MPs were examined by metagenomics and genome binning methods. The results revealed that BMPs harbored rougher surfaces and induced stronger alterations in microbial functional and taxonomic profiles in the soil and plastisphere than PE-MPs. In comparison to their respective soils, the plastispheres of PE-MPs and BMPs stimulated the processes of N fixation, N degradation and assimilatory nitrate reduction (ANRA) and reduced the gene abundances encoding nitrification and denitrification, in which BMPs induced stronger influences than PE-MPs. Ramlibacter mainly drove the differences in N cycling processes between the soils containing two types of MPs and was further enriched in the BMP plastisphere. Three high-quality genomes were identified as Ramlibacter stains with higher abundances in the plastisphere of BMP than that of PE-MP. These Ramlibacter strains had the metabolic capacities of N fixation, N degradation, ANRA and ammonium transport, which were potentially attributed to their biosynthesis and the accumulation of soil NH4+-N. Taken together, our results highlight the genetic mechanisms of soil N bioavailability in the presence of biodegradable MPs, which have important implications for maintaining sustainable agriculture and controlling microplastic risk.