Enzymatic degradation of plant biomass and synthetic polymers

Triggering and identifying the polyurethane and polyethylene-degrading machinery of filamentous fungi secretomes

The uncontrollable disposal of plastic waste has raised the concern of the scientific community, which tries to face this environmental burden by discovering and applying new techniques. Regarding the biotechnology field, several important microorganisms possessing the necessary enzymatic arsenal to utilize recalcitrant synthetic polymers as an energy source have been discovered. In the present study, we screened various fungi for their ability to degrade intact polymers, such as ether-based polyurethane (PU) and low-density polyethylene (LDPE). For this, ImpranIil® DLN-SD and a mixture of long-chain alkanes were used as sole carbon sources, indicating not only the most promising strains in agar plate screening but also inducing the secretion of depolymerizing enzymatic activities, useful for polymer degradation. The agar plate screening revealed three fungal strains belonging to Fusarium and Aspergillus genera, whose secretome was further studied for its ability to degrade the aforementioned non-treated polymers. Specifically for ether-based PU, the secretome of a Fusarium species reduced the sample mass and the average molecular weight of the polymer by 24.5 and 20.4%, respectively, while the secretome of an Aspergillus species caused changes in the molecular structure of LDPE, as evidenced by FTIR. The proteomics analysis revealed that the enzymatic activities induced in presence of Impranil® DLN-SD can be associated with urethane bond cleavage, a fact which was also supported by the observed degradation of the ether-based PU. Although, the mechanism of LDPE degradation was not completely elucidated, the presence of oxidative enzymes could be the main factor contributing to polymer modification.

Deciphering the distinct successional patterns and potential roles of abundant and rare microbial taxa of urban riverine plastisphere

Microbial colonization on microplastics has provoked global concern; however, many studies have not considered the successional patterns and potential roles of abundant and rare taxa of the plastisphere during colonization. Hence, we investigate the taxonomic composition, assembly, interaction and function of abundant and rare taxa in the riverine plastisphere by conducting microcosm experiments. Results showed that rare taxa occupied significantly high community diversity and niche breadth than the abundant taxa, which implies that rare taxa are essential components in maintaining the community stability of the plastisphere. However, the abundant taxa played a major role in driving the succession of plastisphere communities during colonization. Both stochastic and deterministic processes signally affected the plastisphere community assemblies; while, the deterministic patterns (heterogeneous selection) were especially pronounced for rare biospheres. Plastisphere microbial networks were shaped by the enhancement of network modularity and reinforcement of positive interactions. Rare taxa played critical roles in shaping stable plastisphere by occupying the key status in microbial networks. The strong interaction of rare and non-rare taxa suggested that multi-species collaboration might be conducive to the formation and stability of the plastisphere. Both abundant and rare taxa were enriched with plentiful functional genes related to carbon, nitrogen, phosphorus and sulfur cycling; however, their potential metabolic functions were significantly discrepant, implying that the abundant and rare microbes may play different roles in ecosystems. Overall, this study strengthens our comprehending of the mechanisms regarding the formation and maintenance of the plastisphere.

Comparison between discarded facemask and common plastic waste on microbial colonization and physiochemical properties during aging in seawater

Facemasks are indispensable for preventing the spread of COVID-19. However, improper disposal of discarded facemasks has led to their contamination in the marine environment. To understand the environmental risk of this emerging plastic pollution, it's important to clarify the features that distinguish discarded facemasks from common plastic waste during aging. This study compared the microbial colonization, degradation-related enzymes, and physicochemical properties among surgical masks, polystyrene cups, polycarbonate bottles, and polyethylene terephthalate bottles in their aging processes in natural seawater. Compared to the other plastic wastes, surgical masks were colonized by the most diverse microorganisms, reaching 1521 unique prokaryotic OTUs after 21-day exposure in seawater. Moreover, the activity of eukaryotic enzymes associated with plastic degradation was 80-fold higher than that in seawater, indicating that the colonized eukaryotes would be the major microorganisms degrading the surgical masks. Meanwhile, the nano-sized defects (depth between 8 and 61 nm) would evolve into cracks of bigger sizes and result in the breakage of the microfibers and releasing microplastics into the ocean. Overall, our study demonstrated a distinctive plastisphere occurred in surgical masks from both microbial and physiochemical aspects. This work provides new insights for assessing the potential risk of plastic pollution caused by the COVID-19 pandemic.

Gut microbiome of mealworms (Tenebrio molitor Larvae) show similar responses to polystyrene and corn straw diets

BACKGROUND

Some insects can degrade both natural and synthetic plastic polymers, their host and gut microbes play crucial roles in this process. However, there is still a scientific gap in understanding how the insect adapted to the polystyrene (PS) diet from natural feed. In this study, we analyzed diet consumption, gut microbiota responses, and metabolic pathways of Tenebrio molitor larvae exposed to PS and corn straw (CS).

RESULTS

T. molitor larvae were incubated under controlled conditions (25 ± 1 °C, 75 ± 5% humidity) for 30 days by using PS foam with weight-, number-, and size-average molecular weight (Mw, Mn, and Mz) of 120.0, 73.2, and 150.7 kDa as a diet, respectively. The larvae exhibited lower PS consumption (32.5%) than CS (52.0%), and these diets had no adverse effects on their survival. The gut microbiota structures, metabolic pathways, and enzymatic profiles of PS- and CS-fed larvae showed similar responses. The gut microbiota of larvae analysis indicated Serratia sp., Staphylococcus sp., and Rhodococcus sp. were associated with both PS and CS diets. Metatranscriptomic analysis revealed that xenobiotics, aromatic compounds, and fatty acid degradation pathways were enriched in PS- and CS-fed groups; laccase-like multicopper oxidases, cytochrome P450, monooxygenase, superoxidase, and dehydrogenase were involved in lignin and PS degradation. Furthermore, the upregulated gene lac640 in both PS- and CS-fed groups was overexpressed in E. coli and exhibited PS and lignin degradation ability.

CONCLUSIONS

The high similarity of gut microbiomes adapted to biodegradation of PS and CS indicated the plastics-degrading ability of the T. molitor larvae originated through an ancient mechanism that degrades the natural lignocellulose. Video Abstract.

Characterization of plastic degrading bacteria isolated from sewage wastewater

Plastic is a fundamental polymer used in routine life and disposed of in sewage. It leads to microplastic pollution in aquatic organisms, introducing it into the food chain and affecting human health. In the present study, samples were collected from sewage wastewater to isolate the bacteria that could potentially reduce plastic. The six samples were incubated with plastic pieces in minimal salt media for 120 days. After 120 days, the weight loss experiment showed that samples SH5B and SH6B degraded 25% plastic. After chemical and molecular characterization, these strains were identified as Pseudomonas sp. SH5B and Pseudomonas aeruginosa SH6B. The Fourier-transform infrared spectroscopy (FTIR) analysis showed peaks shifting, indicating bond stretching, bond bending, and new bond formation. The Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed various new compounds produced during plastic degradation by these bacterial strains. The plastic biodegradation potential makes these bacteria an impending foundation for green chemistry to eradicate tough pollutants from the environment.

Critical review of phytoremediation for the removal of antibiotics and antibiotic resistance genes in wastewater

Antibiotics in wastewater are a growing environmental concern. Increased prescription and consumption rates have resulted in higher antibiotic wastewater concentration. Conventional wastewater treatment methods are often ineffective at antibiotic removal. Given the environmental risk of antibiotics and associated antibiotic resistant genes (ARGs), finding methods of improving antibiotic removal from wastewater is of great importance. Phytoremediation of antibiotics in wastewater, facilitated through constructed wetlands, has been explored in a growing number of studies. To assess the removal efficiency and treatment mechanisms of plants and microorganisms within constructed wetlands for specific antibiotics of major antibiotic classes, the present review paper considered and evaluated data from the most recent published research on the topics of bench scale hydroponic, lab and pilot scale constructed wetland, and full scale constructed wetland antibiotic remediation. Additionally, microbial and enzymatic antibiotic degradation, antibiotic-ARG correlation, and plant effect on ARGs were considered. It is concluded from the present review that plants readily uptake sulfonamide, macrolide, tetracycline, and fluoroquinolone antibiotics and that constructed wetlands are an effective applied phytoremediation strategy for the removal of antibiotics from wastewater through the mechanisms of microbial biodegradation, root sorption, plant uptake, translocation, and metabolization. More research is needed to better understand the effect of plants on microbial community and ARGs. This paper serves as a synthesis of information that will help guide future research and applied use of constructed wetlands in the field antibiotic phytoremediation and wastewater treatment.

Facile degradation of chitosan-sodium alginate-chromium (III) gel in relation to leather re-tanning and filling

Natural polysaccharide hydrogel, exemplified by chitosan‑sodium alginate (CS-SA), has been prevailing in adsorption of chromium (III) (Cr(III)) containing contaminant. However, the traditional desorption of CS-SA-Cr(III) to recycle the adsorbent faces the problems including chemical desorbents secondary pollution, resource waste of the terminal CS-SA adsorbents, and tedious work of reusing the desorbed Cr(III). Herein, the adsorption product, CS-SA-Cr(III) gel, was degraded to CS/SA/Cr(III) sol and applied in leather re-tanning and filling processes directly. To achieve this goal, three degradation methods were used to transform the gel to sol. Due to the excellent overall performance of the CS/SA/Cr(III)-HMD₄ sol (obtained by the hydrothermal-mechanical degradation method for 4 h (HMD₄)), including wide size and distribution range, moderate viscosity (54 ± 3.1 mPa·s), high electronegativity (-38.6 ± 5.8 mV), and good stability, the resultant leather after re-tanning and filling by the sol achieved fascinating properties such as good thermal stability (T_s, 116.8 ± 1.8 °C; T_d, 94.2 ± 1.7 °C), mechanical performance (tensile strength, 6.9 ± 0.52 MPa; elongation at break, 95 ± 3.0 %), and superduper thickening rate (31.8 %). Moreover, the mechanism of good re-tanning and filling effects was deciphered. Therefore, this work intends to overcome the limitation of traditional desorption technology and further realizes the high-valued application of the exhausted CS-SA-Cr(III) in leather re-tanning and filling processes.

Time-dependent effects of microplastics on soil bacteriome

Microplastic threats to biodiversity, health and ecological safety are adding to concern worldwide, but the real impacts on the functioning of organisms and ecosystems are obscure owing to their inert characteristics. Here we investigated the long-lasting ecological effects of six prevalent microplastic types: polyethylene (PE), polypropylene (PP), polyamide (PA), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) on soil bacteria at a 2 % (w/w) level. Due to the inertia and lack of available nitrogen of these microplastics, their effects on bacteriome tended to converge after one year and were strongly different from their short-term effects. The soil volumes around microplastics were very specific, in which the microplastic-adapted bacteria (e.g., some genera in Actinobacteria) were enriched but the phyla Bacteroidetes and Gemmatimonadetes declined, resulting in higher microbial nitrogen requirements and reduced organic carbon mineralization. The reshaped bacteriome was specialized in the genetic potential of xenobiotic and lipid metabolism as well as related oxidation, esterification, and hydrolysis processes, but excessive oxidative damage resulted in severe weakness in community genetic information processing. According to model predictions, microplastic effects are indirectly derived from nutrients and oxidative stress, and the effects on bacterial functions are stronger than on structure, posing a heavy risk to soil ecosystems.

Metal-organic frameworks and plastic: an emerging synergic partnership

Mismanagement of plastic waste results in its ubiquitous presence in the environment. Despite being durable and persistent materials, plastics are reduced by weathering phenomena into debris with a particle size down to nanometers. The fate and ecotoxicological effects of these solid micropollutants are not fully understood yet, but they are raising increasing concerns for the environment and people's health. Even if different current technologies have the potential to remove plastic particles, the efficiency of these processes is modest, especially for nanoparticles. Metal-organic frameworks (MOFs) are crystalline nano-porous materials with unique properties, have unique properties, such as strong coordination bonds, large and robustus porous structures, high accessible surface areas and adsorption capacity, which make them suitable adsorbent materials for micropollutants. This review examines the preliminary results reported in literature indicating that MOFs are promising adsorbents for the removal of plastic particles from water, especially when MOFs are integrated in porous composite materials or membranes, where they are able to assure high removal efficiency, superior water flux and antifouling properties, even in the presence of other dissolved co-pollutants. Moreover, a recent trend for the alternative preparation of MOFs starting from plastic waste, especially polyethylene terephthalate, as a sustainable source of organic linkers is also reviewed, as it represents a promising route for mitigating the impact of the costs deriving from the widescale MOFs production and application. This connubial between MOFs and plastic has the potential to contribute at implementing a more effective waste management and the circular economy principles in the polymer life cycle.

Complete bio-degradation of poly(butylene adipate-co-terephthalate) via engineered cutinases

Poly(butylene adipate-co-terephthalate) (PBAT), a polyester made of terephthalic acid (TPA), 1,4-butanediol, and adipic acid, is extensively utilized in plastic production and has accumulated globally as environmental waste. Biodegradation is an attractive strategy to manage PBAT, but an effective PBAT-degrading enzyme is required. Here, we demonstrate that cutinases are highly potent enzymes that can completely decompose PBAT films in 48 h. We further show that the engineered cutinases, by applying a double mutation strategy to render a more flexible substrate-binding pocket exhibit higher decomposition rates. Notably, these variants produce TPA as a major end-product, which is beneficial feature for the future recycling economy. The crystal structures of wild type and double mutation of a cutinase from Thermobifida fusca in complex with a substrate analogue are also solved, elucidating their substrate-binding modes. These structural and biochemical analyses enable us to propose the mechanism of cutinase-mediated PBAT degradation.

Enzymes' Power for Plastics Degradation

Plastics are everywhere in our modern way of living, and their production keeps increasing every year, causing major environmental concerns. Nowadays, the end-of-life management involves accumulation in landfills, incineration, and recycling to a lower extent. This ecological threat to the environment is inspiring alternative bio-based solutions for plastic waste treatment and recycling toward a circular economy. Over the past decade, considerable efforts have been made to degrade commodity plastics using biocatalytic approaches. Here, we provide a comprehensive review on the recent advances in enzyme-based biocatalysis and in the design of related biocatalytic processes to recycle or upcycle commodity plastics, including polyesters, polyamides, polyurethanes, and polyolefins. We also discuss scope and limitations, challenges, and opportunities of this field of research. An important message from this review is that polymer-assimilating enzymes are very likely part of the solution to reaching a circular plastic economy.

A Dual Fluorescence Assay Enables High-Throughput Screening for Poly(ethylene terephthalate) Hydrolases

The drastically increasing consumption of petroleum-derived plastics hasserious environmental impacts and raises public concerns. Poly(ethylene terephthalate) (PET) is amongst the most extensively produced synthetic polymers. Enzymatic hydrolysis of PET recently emerged as an enticing path for plastic degradation and recycling. In-lab directed evolution has revealed the great potential of PET hydrolases (PETases). However, the time-consuming and laborious PETase assays hinder the identification of effective variants in large mutant libraries. Herein, we devise and validate a dual fluorescence-based high-throughput screening (HTS) assay for a representative IsPETase. The two-round HTS of a pilot library consisting of 2850 IsPETase variants yields six mutant IsPETases with 1.3-4.9 folds improved activities. Compared to the currently used structure- or computational redesign-based PETase engineering, this HTS approach provides a new strategy for discovery of new beneficial mutation patterns of PETases.

Microbial Enzyme Biotechnology to Reach Plastic Waste Circularity: Current Status, Problems and Perspectives

The accumulation of synthetic plastic waste in the environment has become a global concern. Microbial enzymes (purified or as whole-cell biocatalysts) represent emerging biotechnological tools for waste circularity; they can depolymerize materials into reusable building blocks, but their contribution must be considered within the context of present waste management practices. This review reports on the prospective of biotechnological tools for plastic bio-recycling within the framework of plastic waste management in Europe. Available biotechnology tools can support polyethylene terephthalate (PET) recycling. However, PET represents only ≈7% of unrecycled plastic waste. Polyurethanes, the principal unrecycled waste fraction, together with other thermosets and more recalcitrant thermoplastics (e.g., polyolefins) are the next plausible target for enzyme-based depolymerization, even if this process is currently effective only on ideal polyester-based polymers. To extend the contribution of biotechnology to plastic circularity, optimization of collection and sorting systems should be considered to feed chemoenzymatic technologies for the treatment of more recalcitrant and mixed polymers. In addition, new bio-based technologies with a lower environmental impact in comparison with the present approaches should be developed to depolymerize (available or new) plastic materials, that should be designed for the required durability and for being susceptible to the action of enzymes.

Bamboo for producing charcoal and biochar for versatile applications

Bamboo, the fastest-growing plant, has several unique characteristics that make it appropriate for diverse applications. It is low-cost, high-tensile, lightweight, flexible, durable, and capable of proliferating even in ineffectual areas (e.g., incline). This review discusses the unique properties of bamboo for making charcoal and biochar for diverse applications. To produce bamboo charcoal and biochar, this study reports on the pyrolysis process for the thermal degradation of organic materials in an oxygen-depleted atmosphere under a specific temperature. This is an alternative method for turning waste biomass into products with additional value, such as biochar. Due to various advantages, bamboo charcoal is preferred over regular charcoal as it has four times the absorption rate and ten times more surface area reported. According to the reports, the charcoal yield ranges from 24.60 to 74.27%. Bamboo chopsticks were the most useful source for producing charcoal, with a high yield of 74.27% at 300 °C in nitrogen, but the thorny bamboo species have a tremendous amount of minimal charcoal, i.e., 24.60%. The reported biochar from bamboo yield ranges from 32 to 80%. The most extensive biochar production is produced by the bamboo D. giganteus, which yields 80% biochar at 300 °C. Dry bamboo stalks at 400 °C produced 32% biochar. One of the sections highlights biochar as a sustainable solution for plastic trash management produced during the COVID-19 pandemic. Another section is dedicated to the knowledge enhancement about the broad application spectrum of the charcoal and biochar. The last section highlights the conclusions, future perspectives, and recommendations on the charcoal and biochar derived from bamboo.

Graphical Abstract

Biotechnological methods to remove microplastics: a review

Microplastics pollution is major threat to ecosystems and is impacting abiotic and biotic components. Microplastics are diverse and highly complex contaminants that transport other contaminants and microbes. Current methods to remove microplastics include biodegradation, incineration, landfilling, and recycling. Here we review microplastics with focus on sources, toxicity, and biodegradation. We discuss the role of algae, fungi, bacteria in the biodegradation, and we present biotechnological methods to enhance degradation, e.g., gene editing tools and bioinformatics.

Construction of Fusion Protein with Carbohydrate-Binding Module and Leaf-Branch Compost Cutinase to Enhance the Degradation Efficiency of Polyethylene Terephthalate

Poly(ethylene terephthalate) (PET) is a manufactured plastic broadly available, whereas improper disposal of PET waste has become a serious burden on the environment. Leaf-branch compost cutinase (LCC) is one of the most powerful and promising PET hydrolases, and its mutant LCC^ICCG shows high catalytic activity and excellent thermal stability. However, low binding affinity with PET has been found to dramatically limit its further industrial application. Herein, TrCBM and CfCBM were rationally selected from the CAZy database to construct fusion proteins with LCC^ICCG, and mechanistic studies revealed that these two domains could bind with PET favorably via polar amino acids. The optimal temperatures of LCC^ICCG-TrCBM and CfCBM-LCC^ICCG were measured to be 70 and 80 °C, respectively. Moreover, these two fusion proteins exhibited favorable thermal stability, maintaining 53.1% and 48.8% of initial activity after the incubation at 90 °C for 300 min. Compared with LCC^ICCG, the binding affinity of LCC^ICCG-TrCBM and CfCBM-LCC^ICCG for PET has been improved by 1.4- and 1.3-fold, respectively, and meanwhile their degradation efficiency on PET films was enhanced by 3.7% and 24.2%. Overall, this study demonstrated that the strategy of constructing fusion proteins is practical and prospective to facilitate the enzymatic PET degradation ability.

Bioresource Upgrade for Sustainable Energy, Environment, and Biomedicine

We conceptualize bioresource upgrade for sustainable energy, environment, and biomedicine with a focus on circular economy, sustainability, and carbon neutrality using high availability and low utilization biomass (HALUB). We acme energy-efficient technologies for sustainable energy and material recovery and applications. The technologies of thermochemical conversion (TC), biochemical conversion (BC), electrochemical conversion (EC), and photochemical conversion (PTC) are summarized for HALUB. Microalgal biomass could contribute to a biofuel HHV of 35.72 MJ Kg-1 and total benefit of 749 $/ton biomass via TC. Specific surface area of biochar reached 3000 m2 g-1 via pyrolytic carbonization of waste bean dregs. Lignocellulosic biomass can be effectively converted into bio-stimulants and biofertilizers via BC with a high conversion efficiency of more than 90%. Besides, lignocellulosic biomass can contribute to a current density of 672 mA m-2 via EC. Bioresource can be 100% selectively synthesized via electrocatalysis through EC and PTC. Machine learning, techno-economic analysis, and life cycle analysis are essential to various upgrading approaches of HALUB. Sustainable biomaterials, sustainable living materials and technologies for biomedical and multifunctional applications like nano-catalysis, microfluidic and micro/nanomotors beyond are also highlighted. New techniques and systems for the complete conversion and utilization of HALUB for new energy and materials are further discussed.

Plastic biodegradation by in vitro environmental microorganisms and in vivo gut microorganisms of insects

Traditional plastics, such as polyethylene (PE), polystyrene (PS), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyurethane (PUR), and other plastic polymers, are difficult to degrade and are gradually accumulated in the environment to cause a serious environmental problem, which is urgently needed to develop novel treatments or control technology. The biodegradation of plastics has gained great attention due to the advantages of green and safe characteristics. Microorganisms play a vital role in the biodegradation of plastics, including environmental microbes (in vitro) and gut microbes of insects (in vivo). Microbial degradation in environmental conditions in vitro is extremely slow for major plastics at degradation rates on the basis of a month or even a year time, but recent discoveries show that the fast biodegradation of specific plastics, such as PS, PE, and PUR, in some invertebrates, especially insects, could be enhanced at rates on basis of hours; the biodegradation in insects is likely to be gut microbial-dependent or synergetic bioreactions in animal digestive systems. This review comprehensively summarizes the latest 7-year (2016-2022) publications on plastic biodegradation by insects and microorganisms, elucidates the mechanism of plastic degradation in insects and environmental microbes, and highlights the cutting-edge perspectives for the potential applications of plastic biodegradation.

Dual regulatory effects of microplastics and heat waves on river microbial carbon metabolism

Rivers play a critical role in the global carbon cycle, but the processes can be affected by widespread microplastic (MP) pollution and the increasing frequency of heat waves (HWs) in a warming climate. However, little is known about the role of river microbes in regulating the carbon cycle under the combined action of MP pollution and HWs. Here, through seven-day MP exposure and three cycles of HW simulation experiments, we found that MPs inhibited the thermal adaptation of the microbial community, thus regulating carbon metabolism. The CO₂ release level increased, while the carbon degradation ability and the preference for stable carbon were inhibited. Metabonomic, 16 S rRNA and ITS gene analyses further revealed that the regulation of carbon metabolism was closely related to the microbial r-/K- strategy, community assembly and transformation of keystone taxa. The random forest model revealed that dissolved oxygen and ammonia-nitrogen were important variables influencing microbial carbon metabolism. The above findings regarding microbe-mediated carbon metabolism provide insights into the effect of climate-related HWs on the ecological risks of MPs.

Plastic Eating Enzymes: A Step Towards Sustainability

The large-scale usage of petro-chemical-based plastics has proved to be a significant source of environmental pollution due to their non-biodegradable nature. Microbes-based enzymes such as esterases, cutinases, and lipases have shown the ability to degrade synthetic plastic. However, the degradation of plastics by enzymes is primarily limited by the unavailability of a robust enzymatic system, i.e., low activity and stability towards plastic degradation. Recently, the machine learning strategy involved structure-based and deep neural networks show desirable potential to generate functional, active stable, and tolerant polyethylene terephthalate (PET) degrading enzyme (FAST-PETase). FAST-PETase showed the highest PET hydrolytic activity among known enzymes or their variants and degraded broad ranges of plastics. The development of a closed-loop circular economy-based system of plastic degradation to monomers by FAST-PETase followed by the re-polymerization of monomers into clean plastics can be a more sustainable approach. As an alternative to synthetic plastics, diverse microbes can produce polyhydroxyalkanoates, and their degradation by microbes has been well-established. This article discusses recent updates in the enzymatic degradation of plastics for sustainable development.

Identification of fungal lignocellulose-degrading biocatalysts secreted by Phanerochaete chrysosporium via activity-based protein profiling

Activity-based protein profiling (ABPP) has emerged as a versatile biochemical method for studying enzyme activity under various physiological conditions, with applications so far mainly in biomedicine. Here, we show the potential of ABPP in the discovery of biocatalysts from the thermophilic and lignocellulose-degrading white rot fungus Phanerochaete chrysosporium. By employing a comparative ABPP-based functional screen, including a direct profiling of wood substrate-bound enzymes, we identify those lignocellulose-degrading carbohydrate esterase (CE1 and CE15) and glycoside hydrolase (GH3, GH5, GH16, GH17, GH18, GH25, GH30, GH74 and GH79) enzymes specifically active in presence of the substrate. As expression of fungal enzymes remains challenging, our ABPP-mediated approach represents a preselection procedure for focusing experimental efforts on the most promising biocatalysts. Furthermore, this approach may also allow the functional annotation of domains-of-unknown functions (DUFs). The ABPP-based biocatalyst screening described here may thus allow the identification of active enzymes in a process of interest and the elucidation of novel biocatalysts that share no sequence similarity to known counterparts.

Enhancement of the polyethylene terephthalate and mono-(2-hydroxyethyl) terephthalate degradation activity of Ideonella sakaiensis PETase by an electrostatic interaction-based strategy

The serious environmental pollution that came up with the continuously growing demand for polyethylene terephthalate (PET) has attracted global concern. The IsPETase which has shown the highest PET degradation activity under ambient temperature is a promising enzyme for PET biodegradation, while poor thermostability limited its practical application. Herein, an electrostatic interaction-based strategy was applied for rational design of IsPETase towards enhanced thermostability. The IsPETaseI139R variant displayed the highest Tm value of 56.4 °C and 3.6-times higher PET degradation activity. Molecular simulations demonstrated that the introduction of salt bridges stabilized the local structures, resulting in robust thermostability. Meanwhile, the IsPETaseS92K/D157E/R251A not only exhibited higher thermostability but also showed a 1.74-fold kcat increase towards mono-(2-hydroxyethyl) terephthalate, which ultimately achieved PET depolymerization to complete monomer TPA. Collectively, the electrostatic interaction-based strategy, together with the derived IsPETase variants, could help promote the bio-recycle of PET, reducing the severe global burden of PET waste.

Designed High-Redox Potential Laccases Exhibit High Functional Diversity

White-rot fungi secrete an impressive repertoire of high-redox potential laccases (HRPLs) and peroxidases for efficient oxidation and utilization of lignin. Laccases are attractive enzymes for the chemical industry due to their broad substrate range and low environmental impact. Since expression of functional recombinant HRPLs is challenging, however, iterative-directed evolution protocols have been applied to improve their expression, activity, and stability. We implement a rational, stabilize-and-diversify strategy to two HRPLs that we could not functionally express. First, we use the PROSS stability-design algorithm to allow functional expression in yeast. Second, we use the stabilized enzymes as starting points for FuncLib active-site design to improve their activity and substrate diversity. Four of the FuncLib-designed HRPLs and their PROSS progenitor exhibit substantial diversity in reactivity profiles against high-redox potential substrates, including lignin monomers. Combinations of 3–4 subtle mutations that change the polarity, solvation, and sterics of the substrate-oxidation site result in orders of magnitude changes in reactivity profiles. These stable and versatile HRPLs are a step toward generating an effective lignin-degrading consortium of enzymes that can be secreted from yeast. The stabilize-and-diversify strategy can be applied to other challenging enzyme families to study and expand the utility of natural enzymes.

Novel bacterial taxa in a minimal lignocellulolytic consortium and their potential for lignin and plastics transformation

The understanding and manipulation of microbial communities toward the conversion of lignocellulose and plastics are topics of interest in microbial ecology and biotechnology. In this study, the polymer-degrading capability of a minimal lignocellulolytic microbial consortium (MELMC) was explored by genome-resolved metagenomics. The MELMC was mostly composed (>90%) of three bacterial members (Pseudomonas protegens; Pristimantibacillus lignocellulolyticus gen. nov., sp. nov; and Ochrobactrum gambitense sp. nov) recognized by their high-quality metagenome-assembled genomes (MAGs). Functional annotation of these MAGs revealed that Pr. lignocellulolyticus could be involved in cellulose and xylan deconstruction, whereas Ps. protegens could catabolize lignin-derived chemical compounds. The capacity of the MELMC to transform synthetic plastics was assessed by two strategies: (i) annotation of MAGs against databases containing plastic-transforming enzymes; and (ii) predicting enzymatic activity based on chemical structural similarities between lignin- and plastics-derived chemical compounds, using Simplified Molecular-Input Line-Entry System and Tanimoto coefficients. Enzymes involved in the depolymerization of polyurethane and polybutylene adipate terephthalate were found to be encoded by Ps. protegens, which could catabolize phthalates and terephthalic acid. The axenic culture of Ps. protegens grew on polyhydroxyalkanoate (PHA) nanoparticles and might be a suitable species for the industrial production of PHAs in the context of lignin and plastic upcycling.

Bulk Erosion Degradation Mechanism for Poly(1,8-octanediol-co-citrate) Elastomer: An In Vivo and In Vitro Investigation

As a biodegradable elastomer, poly(1,8-octanediol-co-citrate) (POC) has been widely applied in tissue engineering and implantable electronics. However, the unclear degradation mechanism has posed a great challenge for the better application and development of POC. To reveal the degradation mechanism, here, we present a systematic investigation into in vivo and in vitro degradation behaviors of POC. Initially, critical factors, including chemical structures, hydrophilic and water-absorbency characteristics, and degradation reaction of POC, are investigated. Then, various degradation-induced changes during in vitro degradation of POC-x (POC with different cross-linking densities) are monitored and discussed. The results show that (1) cross-linking densities exponentially drop with degradation time; (2) mass loss and PBS-absorption ratio grow nonlinearly; (3) the morphology on the cross-section changes from flat to rough at a microscopic level; (4) the cubic samples keep swelling until they collapse into fragments from a macro view; and (5) the mechanical properties experience a sharp drop at the beginning of degradation. Finally, the in vivo degradation behaviors of POC-x are investigated, and the results are similar to those in vitro. The comprehensive assessment suggests that the in vitro and in vivo degradation of POC occurs primarily through bulk erosion. Inflammation responses triggered by the degradation of POC-x are comparable to poly(lactic acid), or even less obvious. In addition, the mechanical evaluation of POC in the simulated application environment is first proposed and conducted in this work for a more appropriate application. The degradation mechanism of POC revealed will greatly promote the further development and application of POC-based materials in the biomedical field.

Critical effect of biodegradation on long-term microplastic weathering in sediment environments: A systematic review

Microplastic (MP) pollution in global sediment has been intensely studied and recognized as the ultimate sink for residual MPs in terrestrial and aquatic ecosystems. During MP long-term retention in sediments, plastic-degrading bacteria (i.e., Flavobacteriaceae, Bacillus, Rhodobacteraceae, and Desulfobacteraceae) can utilize those MPs as their carbon and energy sources through enzyme (hydrolase and oxidoreductase) reactions, which further alter or transform high molecular weight MP polymers into lower molecular weight biodegradation byproducts (i.e., monomers and oligomers) and release toxic additives. In other words, MPs can act as durable substrates for plastic-degrading bacteria in sediments. However, to date, the biodegradation rates of MPs in sediment environments are still poorly understood due to their limited degradation efficiency. Herein, we review the enzyme-induced biodegradation processes of MPs in sediment environments, which is important for accessing the alteration of MP properties and their potential ecological risks after undergoing long-term weathering processes. In addition, the factors associated with the MP properties (polymer type, molecular weight, crystallinity, and hydrophobicity) and sediment conditions (sediment type, temperature, pH, salinity, and oxygen content) that influence plastic degradation processes are also reviewed. The mechanisms may relate to the MP properties and sediment conditions that can influence microbial abundance, enzyme concentrations, and enzyme activities, thus altering MP biodegradation ratios. We anticipate that the observations reviewed in this study will pose a new issue to better understand the formation process, fate, and potential ecological risks associated with aged MPs in sediment environments.

Efficient Reaction Systems for Lignocellulosic Biomass Conversion to Furan Derivatives: A Minireview

Lignocellulosic biomass as abundant, renewable, and sustainable carbon feedstock is an alternative to relieve the dependence on fossil fuels and satisfy the demands of chemicals and materials. Conversions of lignocellulosic biomass to high-value-added chemicals have drawn much attention recently due to the high availability of sustainable ways. This minireview surveys the recent trends in lignocellulosic biomass conversion into furan derivatives based on the following systems: (1) ionic liquids, (2) deep eutectic solvents, and (3) biphasic systems. Moreover, the current challenges and future perspectives in the development of efficient routes for lignocellulosic biomass conversion are provided.

Sustainable management of plastic wastes in COVID-19 pandemic: The biochar solution

To prevent the COVID-19 transmission, personal protective equipment (PPE) and packaging materials have been extensively used but often managed inappropriately, generating huge amount of plastic waste. In this review, we comprehensively discussed the plastic products utilized and the types and amounts of plastic waste generated since the outbreak of COVID-19, and reviewed the potential treatments for these plastic wastes. Upcycling of plastic waste into biochar was addressed from the perspectives of both environmental protection and practical applications, which can be verified as promising materials for environmental protections and energy storages. Moreover, novel upcycling of plastic waste into biochar is beneficial to mitigate the ubiquitous plastic pollution, avoiding harmful impacts on human and ecosystem through direct and indirect micro-/nano-plastic transmission routes, and achieving the sustainable plastic waste management for value-added products, simultaneously. This suggests that the plastic waste could be treated as a valuable resource in an advanced and green manner.

Booming microplastics generation in landfill: An exponential evolution process under temporal pattern

Landfills are the main plastic sinks and microplastics (MPs) sources in the anthropogenic terrestrial system. Understanding the dynamic process of generating MPs is a prerequisite to reducing their potential risk, which remains unexplored because of the complex stabilization process of landfills. In this study, we investigated the evolution process of MPs generated in a partitioned landfill, with well-recorded disposal ages of over 30 years. Considering the initial plastic proportions in fresh landfilled waste, the occurrence of MPs increased exponentially with the disposal age. A booming generation of MPs occurred from 71.3 ± 17.7 items/(g plastic) to 653.1 ± 191.5 items/(g plastic). The generation rates of MPs varied greatly depending on the individual polymer types, with polyethylene (PE) having the highest generation rate of 28.4 items/(g plastic) per year at 31 years, compared to that of polypropylene (PP) and polystyrene (PS) at 15.0 and 9.6 items/(g plastic) per year, respectively. The variation in the carbonyl index indicated that environmental oxidation might facilitate the fragmentation of plastic waste. The relative abundance of plastic-degrading microbes increased more than three times in the plastisphere after 30 years of landfilling, indicating that the potential biodegradation might be a nonnegligible driver for plastic fragmentation after long-term natural acclimatization. This study revealed the dynamic evolution process of MPs in landfills and predicted the booming stage, which might provide an important guideline for reducing the leakage risk of MPs during the reclamation of old landfills or dumping sites.

A unified view on catalytic conversion of biomass and waste plastics

Originating from the desire to improve sustainability, producing fuels and chemicals from the conversion of biomass and waste plastic has become an important research topic in the twenty-first century. Although biomass is natural and plastic synthetic, the chemical nature of the two are not as distinct as they first appear. They share substantial structural similarities in terms of their polymeric nature and the types of bonds linking their monomeric units, resulting in close relationships between the two materials and their conversions. Previously, their transformations were mostly studied and reviewed separately in the literature. Here, we summarize the catalytic conversion of biomass and waste plastics, with a focus on bond activation chemistry and catalyst design. By tracking the historical and more recent developments, it becomes clear that biomass and plastic have not only evolved their unique conversion pathways but have also started to cross paths with each other, with each influencing the landscape of the other. As a result, this Review on the catalytic conversion of biomass and waste plastic in a unified angle offers improved insights into existing technologies, and more importantly, may enable new opportunities for future advances.

Biomass and plastic share structural similarities in their composition and types of bond linkage between their monomeric units. Reviewing their catalytic conversion technologies in a unified angle provides new insights and opportunities for future advances.

Polystyrene Degradation by Exiguobacterium sp. RIT 594: Preliminary Evidence for a Pathway Containing an Atypical Oxygenase

The widespread use of plastics has led to their increasing presence in the environment and subsequent pollution. Some microorganisms degrade plastics in natural ecosystems and the associated metabolic pathways can be studied to understand the degradation mechanisms. Polystyrene (PS) is one of the more recalcitrant plastic polymers that is degraded by only a few bacteria. Exiguobacterium is a genus of Gram-positive poly-extremophilic bacteria known to degrade PS, thus being of biotechnological interest, but its biochemical mechanisms of degradation have not yet been elucidated. Based solely on genome annotation, we initially proposed PS degradation by Exiguobacterium sp. RIT 594 via depolymerization and epoxidation catalyzed by a ring epoxidase. However, Fourier transform infrared (FTIR) spectroscopy analysis revealed an increase of carboxyl and hydroxyl groups with biodegradation, as well as of unconjugated C-C double bonds, both consistent with dearomatization of the styrene ring. This excludes any aerobic pathways involving side chain epoxidation and/or hydroxylation. Subsequent experiments confirmed that molecular oxygen is critical to PS degradation by RIT 594 because degradation ceased under oxygen-deprived conditions. Our studies suggest that styrene breakdown by this bacterium occurs via the sequential action of two enzymes encoded in the genome: an orphan aromatic ring-cleaving dioxygenase and a hydrolase.

Current Advances in Biodegradation of Polyolefins

Polyolefins, including polyethylene (PE), polypropylene (PP) and polystyrene (PS), are widely used plastics in our daily life. The excessive use of plastics and improper handling methods cause considerable pollution in the environment, as well as waste of energy. The biodegradation of polyolefins seems to be an environmentally friendly and low-energy consumption method for plastics degradation. Many strains that could degrade polyolefins have been isolated from the environment. Some enzymes have also been identified with the function of polyolefin degradation. With the development of synthetic biology and metabolic engineering strategies, engineered strains could be used to degrade plastics. This review summarizes the current advances in polyolefin degradation, including isolated and engineered strains, enzymes and related pathways. Furthermore, a novel strategy for polyolefin degradation by artificial microbial consortia is proposed, which would be helpful for the efficient degradation of polyolefin.

Merging Plastics, Microbes, and Enzymes: Highlights from an International Workshop

In the Anthropocene, plastic pollution is a worldwide concern that must be tackled from different viewpoints, bringing together different areas of science. Microbial transformation of polymers is a broad-spectrum research topic that has become a keystone in the circular economy of fossil-based and biobased plastics. To have an open discussion about these themes, experts in the synthesis of polymers and biodegradation of lignocellulose and plastics convened within the framework of The Transnational Network for Research and Innovation in Microbial Biodiversity, Enzymes Technology and Polymer Science (MENZYPOL-NET), which was recently created by early-stage scientists from Colombia and Germany. In this context, the international workshop “Microbial Synthesis and Degradation of Polymers: Toward a Sustainable Bioeconomy” was held on 27 September 2021 via Zoom. The workshop was divided into two sections, and questions were raised for discussion with panelists and expert guests. Several key points and relevant perspectives were delivered, mainly related to (i) the microbial evolution driven by plastic pollution; (ii) the relevance of and interplay between polymer structure/composition, enzymatic mechanisms, and assessment methods in plastic biodegradation; (iii) the recycling and valorization of plastic waste; (iv) engineered plastic-degrading enzymes; (v) the impact of (micro)plastics on environmental microbiomes; (vi) the isolation of plastic-degrading (PD) microbes and design of PD microbial consortia; and (vii) the synthesis and applications of biobased plastics. Finally, research priorities from these key points were identified within the microbial, enzyme, and polymer sciences.

Upcycling to Sustainably Reuse Plastics

Plastics are now indispensable in daily lives. However, the pollution from plastics is also increasingly becoming a serious environmental issue. Recent years have seen more sustainable approaches and technologies, commonly known as upcycling, to transform plastics into value-added materials and chemical feedstocks. In this review, the latest research on upcycling is presented, with a greater focus on the use of renewable energy as well as the more selective methods to repurpose synthetic polymers. First, thermal upcycling approaches are briefly introduced, including the redeployment of plastics for construction uses, 3D printing precursors, and lightweight materials. Then, some of the latest novel strategies to deconstruct condensation polymers to monomers for repolymerization or introduce vulnerable linkers to make the plastics more degradable are discussed. Subsequently, the review will explore the breakthroughs in plastics upcycling by heterogeneous and homogeneous photocatalysis, as well as electrocatalysis, which transform plastics into more versatile fine chemicals and materials while simultaneously mitigating global climate change. In addition, some of the biotechnological advances in the discovery and engineering of microbes that can decompose plastics are also presented. Finally, the current challenges and outlook for future plastics upcycling are discussed to stimulate global cooperation in this field.

The eco-friendly approach of cocktail enzyme in agricultural waste treatment: A comprehensive review

Agricultural development over the past decade has majorly contributed to the world's bioeconomy, but is the rise in agricultural activities just resulting in the best? Farming, food processing, livestock handling and other agro-based actions show an incremental rise in environmental deterioration by generating millions of tonnes of organic and inorganic solid waste across the globe. Incautious waste handling practices (incineration and landfilling) is resulting in greenhouse gas emissions, land pollution, groundwater contamination, soil erosion and chronic health hazards. Lately the concept of bioconversion has gained importance in valorising agro-waste (lignocellulosic biomasses) into value added products like biofuels, biogas, single cell proteins and biochar to effectively control waste and reduce the dependency on non-renewable feedstocks (fossil fuels). Biomass hydrolysis via enzymes is improved in terms of cost, efficiency, catalysis, stability and specificity by enrolling the use of enzyme cocktails to synergistically degrade lignocellulose into monomeric sugars and further into valued products. Enzyme blends like that of Xylanase + Pectinase + Cellulase shows 76.5% fermentation within 30 h by using banana peel as substrate for biofuel production. Other sectors like paper industries have also explored the use of enzyme blends of Xylanase + Pectinase + α-amylase + Protease+ lipase for bio-bleaching showing reduction in 50% chemical usage and 19.5% kappa number with adjacent increase in tensile strength by 23.55%. The scope of the present review is to highlight the technicalities of the concepts mentioned above, include qualitative data from different relatable studies and prove how the use of enzyme cocktails is an eco-friendly approach towards agro-waste management.

Lessons From Insect Fungiculture: From Microbial Ecology to Plastics Degradation

Anthropogenic activities have extensively transformed the biosphere by extracting and disposing of resources, crossing boundaries of planetary threat while causing a global crisis of waste overload. Despite fundamental differences regarding structure and recalcitrance, lignocellulose and plastic polymers share physical-chemical properties to some extent, that include carbon skeletons with similar chemical bonds, hydrophobic properties, amorphous and crystalline regions. Microbial strategies for metabolizing recalcitrant polymers have been selected and optimized through evolution, thus understanding natural processes for lignocellulose modification could aid the challenge of dealing with the recalcitrant human-made polymers spread worldwide. We propose to look for inspiration in the charismatic fungal-growing insects to understand multipartite degradation of plant polymers. Independently evolved in diverse insect lineages, fungiculture embraces passive or active fungal cultivation for food, protection, and structural purposes. We consider there is much to learn from these symbioses, in special from the community-level degradation of recalcitrant biomass and defensive metabolites. Microbial plant-degrading systems at the core of insect fungicultures could be promising candidates for degrading synthetic plastics. Here, we first compare the degradation of lignocellulose and plastic polymers, with emphasis in the overlapping microbial players and enzymatic activities between these processes. Second, we review the literature on diverse insect fungiculture systems, focusing on features that, while supporting insects' ecology and evolution, could also be applied in biotechnological processes. Third, taking lessons from these microbial communities, we suggest multidisciplinary strategies to identify microbial degraders, degrading enzymes and pathways, as well as microbial interactions and interdependencies. Spanning from multiomics to spectroscopy, microscopy, stable isotopes probing, enrichment microcosmos, and synthetic communities, these strategies would allow for a systemic understanding of the fungiculture ecology, driving to application possibilities. Detailing how the metabolic landscape is entangled to achieve ecological success could inspire sustainable efforts for mitigating the current environmental crisis.

Short-term exposure to soils and sludge induce changes to plastic morphology and 13C stable isotopic composition

There is concern about the buildup of plastic waste in soil, their degradation into microplastics, and their potential to interfere with the natural processing of soil organic carbon and other nutrient cycling processes. Here we used scanning electron microscopy (SEM) and ¹³C isotope ratio mass spectrometry to determine if precut consumer plastics comprised of either high density polyethylene (HDPE), a blend of linear low density polyethylene and low density polyethylene (L/LDPE), or polyethylene terephthalate (PETE) would degrade or transform during a short-term, 32 day, exposure to soil or sludge in laboratory microcosms. SEM confirmed morphological changes occurred to all plastics, but the attachment of biofilm and presence of microorganisms mostly favored PETE and HDPE surfaces. These observations support the idea that abiotic and/or biotic processes may degrade plastics in soil; however distinguishable and significant changes in mean stable isotopic values (Δδ¹³C) of ~0.2-0.7‰ were only observed for exposed PETE and HDPE. This indicates that each plastic's degradation in soil may be dependent on their physical and chemical properties, with L/LDPE being more resistant and less prone to degradation compared to the others, and less dependent on the environmental conditions or properties of the soil or sludge. Our experiments were short-term and while the mechanisms of degradation are not clear, the results provide strong motivation for further studies of plastic fate and processing in soil systems. Direct mechanistic studies using stable isotopic approaches in combination with other characterizations and techniques are clearly warranted and may lead to a significant enhancement in our present understanding of the interactions and dynamics of plastics in the soil environment.

Machine learning-aided engineering of hydrolases for PET depolymerization

Plastic waste poses an ecological challenge^1-3 and enzymatic degradation offers one, potentially green and scalable, route for polyesters waste recycling⁴. Poly(ethylene terephthalate) (PET) accounts for 12% of global solid waste⁵, and a circular carbon economy for PET is theoretically attainable through rapid enzymatic depolymerization followed by repolymerization or conversion/valorization into other products^6-10. Application of PET hydrolases, however, has been hampered by their lack of robustness to pH and temperature ranges, slow reaction rates and inability to directly use untreated postconsumer plastics¹¹. Here, we use a structure-based, machine learning algorithm to engineer a robust and active PET hydrolase. Our mutant and scaffold combination (FAST-PETase: functional, active, stable and tolerant PETase) contains five mutations compared to wild-type PETase (N233K/R224Q/S121E from prediction and D186H/R280A from scaffold) and shows superior PET-hydrolytic activity relative to both wild-type and engineered alternatives¹² between 30 and 50 °C and a range of pH levels. We demonstrate that untreated, postconsumer-PET from 51 different thermoformed products can all be almost completely degraded by FAST-PETase in 1 week. FAST-PETase can also depolymerize untreated, amorphous portions of a commercial water bottle and an entire thermally pretreated water bottle at 50 ºC. Finally, we demonstrate a closed-loop PET recycling process by using FAST-PETase and resynthesizing PET from the recovered monomers. Collectively, our results demonstrate a viable route for enzymatic plastic recycling at the industrial scale.

Conversion of Plastic Waste to Carbon-Based Compounds and Application in Energy Storage Devices

At present, plastic waste accumulation has been observed as one of the most alarming environmental challenges, affecting all forms of life, economy, and natural ecosystems, worldwide. The overproduction of plastic materials is mainly due to human population explosion as well as extraordinary proliferation in the global economy accompanied by global productivity. Under this threat, the development of benign and green alternative solutions instead of traditional disposal methods such as conversion of plastic waste materials into cherished carbonaceous nanomaterials such as carbon nanotubes (CNTs), carbon quantum dots (CQDs), graphene, activated carbon, and porous carbon is of utmost importance. This critical review thoroughly summarizes the different types of daily used plastics, their types, properties, ways of accumulation and their effect on the environment and human health, treatment of waste materials, conversion of waste materials into carbon-based compounds through different synthetic schemes, and their utilization in energy storage devices particularly in supercapacitors, as well as future perspectives. The main purpose of this review is to help the targeted audience to design their futuristic study in this desired field by providing information about the work done in the past few years.

Catalytic Features and Thermal Adaptation Mechanisms of a Deep Sea Bacterial Cutinase-Type Poly(Ethylene Terephthalate) Hydrolase

Poly (ethylene terephthalate) (PET) plastic is chemically inert and persistent. Massive quantities of PET waste end up in landfill sites and oceans, posing major global pollution concerns. PET degrading enzymes with high efficiency provide plastic recycling and bioremediation possibilities. Here, we report a novel cutinase, MtCut with distinct catalytic behaviors, derived from the deep sea Nocardiopsaceae family strain. Biochemical analyses showed MtCut efficiently hydrolyzed PET at ambient temperatures and in an exo-type manner. The activity and stability of MtCut were enhanced by the addition of calcium ions. Notably, no hydrolysis products inhibition was observed during PET depolymerization, suggesting MtCut is a better biocatalyst when compared to other PET hydrolases. In addition, structural components associated with thermal adaptation were investigated using molecular dynamic (MD) simulations, and key regions regulating MtCut thermostability were identified. Our biochemical and structural analyses of MtCut deepen the understanding of PET hydrolysis by cutinases, and provide invaluable insights on improvement and performance engineering strategies for PET-degrading biocatalysts.

The 3D-Printing-Accelerated Design for a Biodegradable Respirator from Tree Leaves (TRespirator)

The unpredictable coronavirus pandemic (COVID-19) has led to a sudden and massive demand for face masks, leading to severe plastic pollution. Here, we propose a method for manufacturing biodegradable masks using high-precision 3D printing technology, called “TRespirator”, mainly made of banana leaves and dental floss silk fibers. By adding plastic recycling waste appropriately, TRespirator can achieve similar protection and mechanical properties as N95 masks. In addition, microorganisms attracted during the degradation of plant fibers will accelerate the degradation of microplastics. This respirator provides a new idea for solving the global problem of plastic pollution of masks.