Enzymatic Degradation Of Polymers Research Articles

Conformational Selection in Enzyme-Catalyzed Depolymerization of Bio-based Polyesters.

Enzymatic degradation of polymers holds promise for advancing towards a bio-based economy. However, bulky polymers presents challenges in accessibility for biocatalysts, hindering depolymerization reactions. Beyond the impact of crystallinity, polymer chains can reside in different conformations affecting binding efficiency to the enzyme. We previously showed that the gauche and trans chain conformers associated with crystalline and amorphous regions of the synthetic polyethylene terephthalate (PET) display different affinity to PETase, thus affecting the depolymerization rate. However, structural-function relationships for biopolymers remain poorly understood in biocatalysis. In this study, we explored biodegradation of by-us previously synthesized bio-polyesters made from a rigid bicyclic chiral terpene-based diol and copolymerized with various renewable diesters. Herein, four of those polyesters spanning from semi-aromatic to aliphatic were subjected to enzymatic degradations in concert with induced-fit docking (IFD) analyses. Our findings demonstrate the importance of conformational selection in enzymatic depolymerization of biopolymers. A straight or twisted conformation of the polymer chain is crucial in biocatalytic degradation by showing different affinities to enzyme ground-state conformers. This work highlights the importance of considering the conformational match between the polymer and the enzyme to optimize the biocatalytic degradation efficiency of biopolymers, providing valuable insights for the development of sustainable bioprocesses.

Enhancing plastic waste recycling: Evaluating the impact of additives on the enzymatic polymer degradation

While (bio)degradation of polymers is a recognized challenge, the influence of additives on this process remains poorly understood. Their presence in commercial polyethylene (PE) may inhibit the degradation process or complicate the recycling. This study aims to develop an enzymatic degradation process for post-consumer high-density polyethylene (HDPE). The HDPE degradation was performed using laccase from Trametes versicolor under mild conditions of temperature and pressure. The process was developed by exploring three key conditions: (i) the biocatalytic medium; (ii) the enzymatic mediator, and (iii) the influence of the presence of additives in the polymers. The most successful enzymatic degradation system involved HDPE from which additives were removed, with a buffer used as the reaction medium and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) employed as the enzymatic mediator. This system led to a substantial 33% weight reduction of the polymer (versus 3% for HDPE with additive under the same conditions). The characterization of the degraded polymer revealed new bands in the Fourier transform infrared spectroscopy (FTIR) spectra, including a new carbonyl band. In addition, it also showed an increased crystallinity when compared to HDPE with additive under the same conditions. These results suggest that the enzymatic degradation of HDPE occurs through an oxidation process, with the enzyme preferentially attacking the amorphous region of the polymer.

Screening the Degradation of Polymer Microparticles on a Chip.

Enzymatic degradation of polymers has advantages over standard degradation methods, such as soil burial and weathering, which are time-consuming and cannot provide time-resolved observations. We have developed a microfluidic device to study the degradation of single microparticles. The enzymatic degradation of poly (1,4-butylene adipate-co-terephthalate) (PBAT) microparticles was studied using Novozym 51032 cutinase. PBAT microparticles were prepared via an oil-in-water emulsion solvent removal method, and their morphology and chemical composition were characterized. Then, microparticles with varying diameters of 30-60 μm were loaded into the microfluidic chip. Enzyme solutions at different concentrations were introduced to the device, and changes in the size and transparency of PBAT microparticles were observed over time. The physicochemical properties of degraded products were analyzed by FT-IR, NMR, mass spectrometry, and differential scanning calorimetry. The degradation process was also performed in bulk, and the results were compared to those of the microfluidic method. Our analysis confirms that the degradation process in both bulk and microfluidic methods was similar. In both cases, degradation takes place on aliphatic and soft segments of PBAT. Our findings serve as a proof of concept for a microfluidic method for easy and time-resolved degradation analysis, with degradation results comparable to those of conventional bulk methods.

Uncovering the Magnetic Particle Imaging and Magnetic Resonance Imaging Features of Iron Oxide Nanocube Clusters.

Multifunctional imaging nanoprobes continue to garner strong interest for their great potential in the detection and monitoring of cancer. In this study, we investigate a series of spatially arranged iron oxide nanocube-based clusters (i.e., chain-like dimer/trimer, centrosymmetric clusters, and enzymatically cleavable two-dimensional clusters) as magnetic particle imaging and magnetic resonance imaging probes. Our findings demonstrate that the short nanocube chain assemblies exhibit remarkable magnetic particle imaging signal enhancement with respect to the individually dispersed or the centrosymmetric cluster analogues. This result can be attributed to the beneficial uniaxial magnetic dipolar coupling occurring in the chain-like nanocube assembly. Moreover, we could effectively synthesize enzymatically cleavable two-dimensional nanocube clusters, which upon exposure to a lytic enzyme, exhibit a progressive increase in magnetic particle imaging signal at well-defined incubation time points. The increase in magnetic particle imaging signal can be used to trace the disassembly of the large planar clusters into smaller nanocube chains by enzymatic polymer degradation. These studies demonstrate that chain-like assemblies of iron oxide nanocubes offer the best spatial arrangement to improve magnetic particle imaging signals. In addition, the nanocube clusters synthesized in this study also show remarkable transverse magnetic resonance imaging relaxation signals. These nanoprobes, previously showcased for their outstanding heat performance in magnetic hyperthermia applications, have great potential as dual imaging probes and could be employed to improve the tumor thermo-therapeutic efficacy, while offering a readable magnetic signal for image mapping of material disassemblies at tumor sites.

Influence of malt modification and the corresponding macromolecular profile on palate fullness in cereal-based beverages

The sensory attribute palate fullness of cereal-based beverages was shown to be affected by polymeric compounds and their macromolecular profile. During malting, the enzymatic degradation of polymers is technologically controlled by the malting parameters, namely the degree of steeping, germination time, and germination temperature. The macromolecular profile of a fermented cereal-based beverage consists of non-fermentable substance classes. Therefore, the macromolecular composition of a final beverage is originally dominated by the raw material, if conventional production methods are used. We investigated the influence of different cytolytic and proteolytic malt modifications on the macromolecular profile of lactic acid-fermented cereal-based beverages (a strain was selected that did not produce exopolysaccharides) and their resultant effect on the sensory perception of the attributes of palate fullness and mouthfeel. Asymmetrical-flow field-flow fractionation coupled with multi-angle light-scattering detection and refractive index detection is an analytical tool for macromolecular characterization to indicate differences in the macromolecular profile, molar mass, and molar mass distribution. The beverages produced using different modified malts demonstrated a considerable variation in their final composition, particularly in the composition of their macromolecular compounds. A higher level of malt modification led to a decrease in the high-molar-mass fraction and a consequent shift toward fractions with a lower molar mass. Malts produced from barley with increased crude protein contents resulted in a greater range within the macromolecular profile. The variation of germination time significantly influenced the number average molar mass, the total refractive index detection (dRI) peak area, and the high-molar-mass fraction, which contained cell wall polysaccharides (60–1200 kDa). The perception of the intensity of palate fullness was significantly correlated with specific macromolecular fractions, which were influenced by the malting parameter degree of steeping and the resultant modification. The perception of the mouthfeel descriptor watery varied significantly for different crude protein contents. Our results are beneficial for a targeted design of beverage composition based on the macromolecular profile by an improved selection of raw materials and malting technology.

Enzyme-Embedded Degradation of Poly(ε-caprolactone) using Lipase-Derived from Probiotic Lactobacillus plantarum.

Enzyme-embedded polymer degradation was reported to be an attractive alternative approach to the conventional surface pouring method for efficient degradation of polymers using fungal-derived enzyme Candida antarctica lipase B. Despite the enormous potential, this approach is still in its infancy. In the present study, a probiotic lipase obtained from Lactobacillus plantarum has been employed for the first time to study the enzyme-embedded polymer degradation approach using poly(ε-caprolactone) (PCL) as the semicrystalline polymer candidate. PCL films embedded with 2 to 8 wt % lipase are studied under static conditions for their enzymatic degradation up to 8 days of incubation. Thermogravimetric analyses (TGA) have shown a clear trend in decreasing thermal stability of the polymer with increasing lipase content and number of incubation days. Differential thermal analyses have revealed that the percentage crystallinity of the leftover PCL films increases with progress in enzymatic degradation because of the efficient action of lipase over the amorphous regions of the films. Thus, the higher lipase loading in the PCL matrix and more number of incubation days have resulted in higher percentage crystallinity in the leftover PCL films, which has further been corroborated by X-ray diffraction analyses. In a similar line, higher percentage mass loss of the PCL films has been observed with increased enzyme loading and number of incubation days. Field emission scanning electron microscopy (FE-SEM) has been employed to follow the surface and cross-sectional morphologies of the polymer films, which has revealed micron-scale pores on the surface as well as a bulk polymer matrix with progress in enzymatic polymer degradation. Additionally, FE-SEM studies have revealed the efficient enzyme-catalyzed hydrolysis of the polymer matrix in a three-dimensional fashion, which is unique to this approach. In addition to the first-time utility of a probiotic lipase for the embedded polymer degradation approach, the present work provides insight into the PCL degradation under static and ambient temperature conditions with no replenishment of enzymes.

Localized Enzymatic Degradation of Polymers: Physics and Scaling Laws

The breakdown of polymers by enzymes is of key importance in chemical engineering, biotechnology, and nature. The process involves a localized, moving front of degradation within the polymer, but little is known about its physical character. This analysis shows that the front's width and propagation speed depend on the physical properties (size, structure, and reactivity) of both enzyme and polymer. Based on competition between reaction and transport of enzymes, simple scaling laws are obtained. These results will facilitate applications of such systems in tissue regeneration, targeted drug delivery, and biomass processing for energy generation.

Strain-specific consumption and transformation of alga-derived dissolved organic matter by members of the Limnohabitans-C and Polynucleobacter-B clusters of Betaproteobacteria.

We investigated changes in quality and quantity of extracellular and biomass-derived organic matter (OM) from three axenic algae (genera Rhodomonas, Chlamydomonas, Coelastrum) during growth of Limnohabitans parvus, Limnohabitans planktonicus and Polynucleobacter acidiphobus representing important clusters of freshwater planktonic Betaproteobacteria. Total extracellular and biomass-derived OM concentrations from each alga were approximately 20 mg l-1 and 1 mg l-1 respectively, from which up to 9% could be identified as free carbohydrates, polyamines, or free and combined amino acids. Carbohydrates represented 54%-61% of identified compounds of the extracellular OM from each alga. In biomass-derived OM of Rhodomonas and Chlamydomonas 71%-77% were amino acids and polyamines, while in that of Coelastrum 85% were carbohydrates. All bacteria grew on alga-derived OM of Coelastrum, whereas only Limnohabitans strains grew on OM from Rhodomonas and Chlamydomonas. Bacteria consumed 24%-76% and 38%-82% of all identified extracellular and biomass-derived OM compounds respectively, and their consumption was proportional to the concentration of each OM compound in the different treatments. The bacterial biomass yield was higher than the total identifiable OM consumption indicating that bacteria also utilized other unidentified alga-derived OM compounds. Bacteria, however, also produced specific OM compounds suggesting enzymatic polymer degradation or de novo exudation.

Introduction of Enzymatic Polymer Degradation to enhance the Undergraduate Polymer Chemistry Curriculum

Changes to the 2015 ACS Guidelines and Evaluation Procedures for Bachelor's Degree Programs included mandatory instruction in polymers and macromolecules for the ACS‐certified degrees. To satisfy this mandate, we have begun developing a series of undergraduate laboratory exercises involving the synthesis, degradation, and characterization of poly(aspartic acid) (PAA). PAA, a biodegradable, water‐soluble synthetic polymer, could potentially replace commonly used poly(acrylic acid), which is a non‐biodegradable polymer that possess environmental risks. In this module of experiments, PAA is prepared in the organic chemistry laboratory course by polymerizing aspartic acid to form poly(succinimide) as an intermediate, which is converted to PAA by base induced ring‐opening. The synthetic PAA, composed of both β‐amide (70%) and α‐amide units (30%), is then transferred to the biochemistry laboratory course for enzymatic biodegradation using two enzymes, PAA hydrolase‐1 (PAAH‐1) and PAA hydrolase‐2 (PAAH‐2). A proposed mechanism suggests that PAAH‐1 hydrolyzes β‐β amide linkages, resulting in oligo (aspartic acid), wherein PAAH‐2 completes the degradation process by cleaving the oligo (aspartic acid) units into monomeric aspartic acid. Current progress on the development of this biochemistry laboratory exercise including overexpression of recombinant PAAH‐1 and PAAH‐2, purification, and characterization will be presented.Support or Funding InformationDUE 1611988

Enzymatic degradation of polymers: a brief review

Recently, research on polymer has drawn much attention mainly due to the ever increasing application of these polymeric materials in several areas such as food packaging industry, agricultural industry and biomedical research. However, increasing industrial use of polymers has led to the environmentally critical issue of waste disposal. Further, the successful implication of polymeric materials in biomedical applications depends on the biodegradability of the concerned polymer. Various enzymes play an important role in the biodegradation of polymers. The present review describes the enzyme mediated biodegradation of various polymers including synthetic, natural and blends of these materials. Detailed examples of enzymatic degradation of polymers are illustrated from current scientific literature with the discussion on various factors that can influence the degradation. In addition, different techniques that are generally applied to assess the degradation process as well as degradation products have been described. Finally, a special emphasis is given to the investigation of the kinetics of polymer degradation by enzymes.

The enzymatic degradation of polymers in vitro.

Specimens of 14C-labeled poly(ethylene terephthalate), nylon 66, and poly(methyl methacrylate) have been synthesized and exposed, in vitro, to a number of enzyme solutions. Poly(ethylene terephthalate) was found to be affected by esterase and papain, although in different ways, but not by trypsin or chymotrypsin. Nylon 66 was unaffected by esterase but degraded by the other three. Poly(methyl methacrylate) was not affected by any of these enzymes. This indicates that some nominally stable polymers are susceptible to degradation by enzymes under some circumstances. The amount of degradation is small, but could have significant sequelae should it be reproduced in vivo.