Enzymatic Degradation Process Research Articles

Characterization and removal mechanism of fluoroquinolone-bioremediation by fungus Cladosporium cladosporioides 11 isolated from aquacultural sediments.

Antibiotics have been widely detected in aquatic environments, and fungal biotransformation receives considerable attention for antibiotic bioremediation. Here, a fungus designated Cladosporium cladosporioides 11 (CC11) with effective capacity to biotransform fluoroquinolones was isolated from aquaculture pond sediments. Enrofloxacin (ENR), ciprofloxacin (CIP) and ofloxacin (OFL) were considerably abated by CC11, and the antibacterial activities of the fluoroquinolones reduced significantly after CC11 treatment. Transcriptome analysis showed the removal of ENR, CIP and OFL by CC11 is a process of enzymatic degradation and biosorption which consists well with ligninolytic enzyme activities and sorption experiments under the same conditions. Additionally, CC11 significantly removed ENR in zebrafish culture water and reduced the residue of ENR in zebrafish. All these results evidenced the potential of CC11 as a novel environmentally friendly process for the removal of fluoroquinolones from aqueous systems and reduce fluoroquinolone residues in aquatic organisms.

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.

Degradation kinetics of medium chain length Polyhydroxyalkanoate degrading enzyme: a quartz crystal microbalance study.

This study investigates the enzymatic degradation processes of different classes of polyhydroxyalkanoates (PHAs), a group of biopolymers naturally synthesized by various microorganisms. Medium chain length PHAs (mcl-PHAs) are distinguished biopolymers due to their biodegradability and diverse material properties. Using quartz crystal microbalance measurements as a valuable tool for accurate real-time monitoring of the enzymatic degradation process, the research provides detailed kinetic data, describing the interaction between enzymes and substrates during the enzymatic degradation process. Thin films of poly-3-hydroxybutyrate (PHB) and polyhydroxyoctanoate copolymer (PHO), containing molar fractions of about 84% 3-hydroxyoctanoate and 16% 3-hydroxyhexanoate, were exposed to scl-depolymerases from Pseudomonas lemoignei LMG 2207 and recombinant mcl-depolymerase produced in Escherichia coli DH5α harboring the plasmid pMAD8, respectively. Analyses based on a heterogeneous kinetic model for the polymer degradation indicated a six-fold stronger adsorption equilibrium constant of mcl-depolymerase to PHO. Conversely, the degradation rate constant was approximately twice as high for scl-depolymerases acting on PHB. Finally, the study highlights the differences in enzyme-substrate interactions and degradation mechanisms between the investigated scl- and mcl-PHAs.

Recyclable pickering emulsions for enzymatic phenol degradation of oily wastewater

Enzymatic degradation offers a sustainable solution for waterborne phenolic pollutants. However, its application within industrial, non-aqueous contexts — particularly in mitigating phenolic contaminants in oily wastewater — remains significantly challenging. To address this challenge, the present study exploits the potential of Fe3O4 @PDA nanoparticles to form oil-in-water Pickering emulsions for the enzymatic degradation process. The uniform stability of the prepared emulsion, with droplet sizes under 5 µm, protects enzyme activity and expands the water-oil interfacial area, leading to an enhancement in the efficiency of horseradish peroxidase (HRP) catalytic degradation. The application of this emulsion resulted in a substantial increase in the degradation rate of phenol, achieving 100% within 30 min as opposed to an only 13.6% without it. The study also highlights the excellent stability, reusability, and versatility of the Fe3O4 @PDA nanoparticles, enabled by magnetic separation and their ability to form emulsions with diverse oil phases. Consequently, our research offers valuable insights into the development of environmentally sustainable strategies for the degradation of phenolic contaminants in various industrial oily wastewater.

Analysis of the enzymatic degradation of lysozyme fibrils using a combination method of non-denaturing gel electrophoresis and double staining with Coomassie Brilliant Blue G-250 and R-250 dyes.

The Amyloid fibrils of proteins are involved in various diseases, such as Alzheimer's disease. To suppress such amyloid fibrils, it is essential to develop methods to elucidate their enzymatic degradation process. Lysozyme in egg white has been well studied as a model protein of amyloid fibrils. Here, we establish a method for separating and evaluating both lysozyme fibrils and their enzymatic degradation products by combining non-denaturing gel electrophoresis and anionic dye staining with Congo red and two Coomassie brilliant blue (CBB) dyes. By combining non-denaturing gel electrophoresis and amyloid-specific Congo red staining, the separation site of lysozyme fibril was stained explicitly by Congo red and identified on the gel, and the amount of lysozyme fibrils decreased following the enzymatic degradation of lysozyme fibrils. Both lysozyme fibrils and their enzymatic degradation products were separated and examined by combining non-denaturing gel electrophoresis and double staining with CBB G-250 and R-250 dyes. Protein stained with negatively charged colloidal CBB G-250 could migrate to the anode side of electrophoresis. Following gel electrophoresis, noncolloidal CBB R-250 was used to detect lysozyme fibrils and the enzymatic degradation products. This method can be applied to investigate the enzymatic degradation process of amyloid fibrils.

Biodegradation of highly crystallized poly(ethylene terephthalate) through cell surface codisplay of bacterial PETase and hydrophobin

The process of recycling poly(ethylene terephthalate) (PET) remains a major challenge due to the enzymatic degradation of high-crystallinity PET (hcPET). Recently, a bacterial PET-degrading enzyme, PETase, was found to have the ability to degrade the hcPET, but with low enzymatic activity. Here we present an engineered whole-cell biocatalyst to simulate both the adsorption and degradation steps in the enzymatic degradation process of PETase to achieve the efficient degradation of hcPET. Our data shows that the adhesive unit hydrophobin and degradation unit PETase are functionally displayed on the surface of yeast cells. The turnover rate of the whole-cell biocatalyst toward hcPET (crystallinity of 45%) dramatically increases approximately 328.8-fold compared with that of purified PETase at 30 °C. In addition, molecular dynamics simulations explain how the enhanced adhesion can promote the enzymatic degradation of PET. This study demonstrates engineering the whole-cell catalyst is an efficient strategy for biodegradation of PET.

Fabrication of a stepwise degradable hybrid bioscaffold based on the natural and partially denatured collagen

As a major component of extracellular matrixes (ECMs), collagen is an attractive biomaterial to fabricate porous scaffold for tissue engineering due to their similarity to the in vivo static microenvironment. However, the collagen-based porous scaffolds were difficult to mimic the dynamically remolded porous structure of ECM during the cell proliferation and tissue development, and always have poor mechanical property and not easy to handle. Here, natural collagen and partially denatured collagen was used to prepare the stepwise degradable hybrid bioscaffold with suitable mechanical property and dynamically remolded inner porous structure, which is desirable for the applications of tissue engineering. The collagen-based microporous scaffold was first prepared and used as physical support, then, the mechanical strength of which was reinforced by the import of the partially denatured collagen to give the hybrid bioscaffold. The fabrication conditions of the hybrid scaffolds were optimized, of which the thermal stability, mechanical property, and swelling property was explored. The stepwise enzymatic degradation process and the corresponding porous structure variation of the hybrid scaffold was confirmed by SEM and cell culture assays.

Sabatier Principle for Rationalizing Enzymatic Hydrolysis of a Synthetic Polyester.

Interfacial enzyme reactions are common in Nature and in industrial settings, including the enzymatic deconstruction of poly(ethylene terephthalate) (PET) waste. Kinetic descriptions of PET hydrolases are necessary for both comparative analyses, discussions of structure–function relations and rational optimization of technical processes. We investigated whether the Sabatier principle could be used for this purpose. Specifically, we compared the kinetics of two well-known PET hydrolases, leaf-branch compost cutinase (LCC) and a cutinase from the bacterium Thermobifida fusca (TfC), when adding different concentrations of the surfactant cetyltrimethylammonium bromide (CTAB). We found that CTAB consistently lowered the strength of enzyme–PET interactions, while its effect on enzymatic turnover was strongly biphasic. Thus, at gradually increasing CTAB concentrations, turnover was initially promoted and subsequently suppressed. This correlation with maximal turnover at an intermediate binding strength was in accordance with the Sabatier principle. One consequence of these results was that both enzymes had too strong intrinsic interaction with PET for optimal turnover, especially TfC, which showed a 20-fold improvement of kcat at the maximum. LCC on the other hand had an intrinsic substrate affinity closer to the Sabatier optimum, and the turnover rate was 5-fold improved at weakened substrate binding. Our results showed that the Sabatier principle may indeed rationalize enzymatic PET degradation and support process optimization. Finally, we suggest that future discovery efforts should consider enzymes with weakened substrate binding because strong adsorption seems to limit their catalytic performance.

Effect of traditional and dry package ageing on physicochemical properties and protein digestibility of pork Longissimus thoracis muscle

The aim of the study was to evaluate the effect of traditional (unpacked) and dry package ageing on quality characteristics, proteolysis and protein digestibility of pork loins aged for 28 days. Changes in pH and weight loss as a function of ageing were more pronounced in traditionally aged loin in comparison to that aged in a bag. Both traditional and bag ageing induced the enzymatic protein degradation process. However, higher amounts of protein degradation products were observed for in bag aged samples compared to traditionally aged samples. The effect of ageing on protein digestibility was evaluated using a simulated in vitro oral-gastrointestinal digestion model. A significant (P < 0.05) impact of ageing was observed and the protein digestibility of the samples showed an increasing trend with ageing time. This was reflected in the results of peptide concentration and free amino acids which showed a significantly increasing trend (P < 0.05) with increased ageing time. A higher degree of protein hydrolysis and higher concentration of peptides were observed for most of the in bag aged samples compared to traditionally aged samples. These results indicate the superiority of in bag ageing in terms of protein digestibility.

Biodegradation of polymers in managing plastic waste — A review

The modern economy that is fast-moving and convenience centric has led to excessive consumption of plastic. This has unwittingly led to egregious accumulation of plastic waste polluting the environment. Unfortunately, present means of plastic waste management have all been proven as less than adequate; namely recycling, landfill and incineration. Recent focus on plastic waste management has seen the confluence of the developments in biodegradable polymers and microbial engineering strategy for more expedient decomposition of plastic waste at composting facilities. This review paper is an assimilation of current developments in the areas of biodegradable polymer as well as microbial strategy towards management of polymer waste. Advents in biodegradable polymers have been promising, especially with aliphatic polyesters and starch in blends or co-polymers of these. Microbial strategies have been pursued for the identification of microbial strains and understanding of their enzymatic degradation process on polymers. New insights in these two areas have been focused in improving the rate of degradation of plastic waste at composting facilities. Recent alignment of testing and certification standards is outlined to give intimate insights into the mechanisms and factors influencing biodegradation. Despite recent milestones, economic viability of composting plastic waste in mainstream waste facilities is still a distance away. As it remains that a polymer that is biodegradable is functionally inferior to conventional polymers. Rather, it requires a shift in consumer behaviour to accept less durable biodegradable plastic products, this will then lower the threshold for biodegradable polymers to become a commercial reality.

Unveiling the Enzymatic Degradation Process of Biobased Thiophene Polyesters.

In the past 20 years, scientific research focused on the identification of valid alternatives to materials of fossil origin, in particular, related to biobased polymers. Recently, the efforts led to the synthesis of thiophene-based polymers (TBPs), a new class of polyesters based on 2,5-thiophenedicarboxylic acid (TPCA) that can be industrially produced using biomass-derived molecules. In this study, TBPs were synthesized using diols with different chain length (from C4 to C6) leading to poly(butylene 2,5-thiophenedicarboxylate) (PBTF), poly(pentamethylene 2,5-thiophenedicarboxylate) (PPeTF), and poly(hexamethylene 2,5-thiophenedicarboxylate) (PHTF), respectively, that were processed to thin films. To investigate enzymatic hydrolysis of these polymer films, cutinase 1 (Thc_cut1) and cutinase 2 (Thc_cut2) from Thermobifida cellulosilytica were recombinantly expressed in the host E. coli and purified. After 72 h of incubation at 65°C with 5 µM Thc_cut1, weight loss and HPLC analysis indicated 9, 100, and 80% degradation of PBTF, PPeTF, and PHTG with a concomitant release of 0.12, 2.70, and 0.67 mM of TPCA. The SEM analysis showed that tiny holes were formed on the surface of the films and after 72 h PPeTF was completely degraded. The LC-TOF/MS analysis indicated that Thc_cut2 in particular released various oligomers from the polymer during the reaction. In addition, the FTIR analysis showed the formation of novel acid and hydroxyl groups on the polymer surfaces. The results showed that the two used thermostable cutinases are promising biocatalysts for the environmentally friendly degradation of TPCA-based polyesters, in view of a possible sustainable recycling of plastic waste through resynthesis processes.

In Situ, Noncovalent Labeling and Stimulated Emission Depletion-Based Super-Resolution Imaging of Supramolecular Peptide Nanostructures.

Supramolecular materials have gained substantial interest for a number biological and nonbiological applications. However, for optimum utilization of these dynamic self-assembled materials, it is important to visualize and understand their structures at the nanoscale, in solution and in real time. Previous approaches for imaging these structures have utilized super-resolution optical imaging methods such as STORM, which has provided important insights, but suffers from drawbacks of complex sample preparation and slow acquisition times, thus limiting real-time in situ imaging of dynamic processes. We demonstrate a noncovalent fluorescent labeling design for STED-based super-resolution imaging of self-assembling peptides. This is achieved by in situ, electrostatic binding of anionic sulfonates of Alexa-488 dye to the cationic sites of lysine (or arginine) residues exposed on the peptide nanostructure surface. A direct, multiscale visualization of static structures reveals hierarchical organization of supramolecular fibers with sub-60 nm resolution. In addition, the degradation of nanofibers upon enzymatic hydrolysis of peptide could be directly imaged in real time, and although resolution was compromised in this dynamic process, it provided mechanistic insights into the enzymatic degradation process. Noncovalent Alexa-488 labeling and subsequent imaging of a range of cationic self-assembling peptides and peptide-functionalized gold nanoparticles demonstrated the versatility of the methodology for the imaging of cationic supramolecular structures. Overall, our approach presents a general and simple method for the electrostatic fluorescent labeling of cationic peptide nanostructures for nanoscale imaging under physiological conditions and probe dynamic processes in real time and in situ.

Effect of concentration of porang flour and temperature on rheological properties of tomato ketchup

The rheological properties of fluid and semisolid foodstuffs is important in the design of flow processes in the quality control, storage stability, and in understanding and designing texture of the product. The viscosity of tomato ketchup is one of the major quality components for consumer acceptance. The tomato ketchup is a semisolid material, which obtain its viscosity from naturally occurring pectic substances in fruits. Enzymatic degradation, pectic/protein interaction, pulp content, and homogenization process may affect the consistency of tomato product. These inconsistencies may be diminished by the addition of hydrocolloids. In this study, the flow properties of tomato ketchup were evaluated upon addition of different concentrations of porang flour (0.25%, 0.50% and 0.75%) and in various temperatures (25, 35, 45 and 55 °C). The flow behaviour was characterized by fitting the experimental data of each formulations to the power-law and Herschel-Bulkley model. The Arrhenius equation was used to describe the effects of temperature on the apparent viscosity of the tomato ketchup formulations. The temperature dependency was assessed to evaluate the stabilizing effect of different concentrations of porang flour on tomato ketchup. Increasing porang flour concentration in tomato ketchup resulted in a decline of the activation energy.

Chondrogenic phenotype in responses to poly(ɛ-caprolactone) scaffolds catalyzed by bioenzymes: effects of surface topography and chemistry

Biodegradable poly(ε-caprolactone) (PCL) has been increasingly investigated as a promising scaffolding material for articular cartilage tissue repair. However, its use can be limited due to its surface hydrophobicity and topography. In this study, 3D porous PCL scaffolds fabricated by a fused deposition modeling (FDM) machine were enzymatically hydrolyzed using two different biocatalysts, namely Novozyme®435 and Amano lipase PS, at varied treatment conditions in a pH 8.0 phosphate buffer solution. The improved surface topography and chemistry of the PCL scaffolds were anticipated to ultimately boost the growth of porcine articular chondrocytes and promote the chondrogenic phenotype during cell culture. Alterations in surface roughness, wettability, and chemistry of the PCL scaffolds after enzymatic treatment were thoroughly investigated using several techniques, e.g., SEM, AFM, contact angle and surface energy measurement, and XPS. With increasing enzyme content, incubation time, and incubation temperature, the surfaces of the PCL scaffolds became rougher and more hydrophilic. In addition, Novozyme®435 was found to have a higher enzyme activity than Amano lipase PS when both were used in the same enzymatic treatment condition. Interestingly, the enzymatic degradation process rarely induced the deterioration of compressive strength of the bulk porous PCL material and slightly reduced the molecular weight of the material at the filament surface. After 28 days of culture, both porous PCL scaffolds catalyzed by Novozyme®435 and Amano lipase PS could facilitate the chondrocytes to not only proliferate properly, but also function more effectively, compared with the non-modified porous PCL scaffold. Furthermore, the enzymatic treatments with 50 mg of Novozyme®435 at 25 °C from 10 min to 60 min were evidently proven to provide the optimally enhanced surface roughness and hydrophilicity most significantly favorable for induction of chondrogenic phenotype, indicated by the greatest expression level of cartilage-specific gene and the largest production of total glycosaminoglycans.

Family-level diversity of extracellular proteases of sedimentary bacteria from the South China Sea

Protease-producing bacteria and their extracellular proteases are key players in degrading organic nitrogen to drive marine nitrogen cycling and yet knowledge on both of them is still very limited. This study screened protease-producing bacteria from the South China Sea sediments and analyzed the diversity of their extracellular proteases at the family level through N-terminal amino acid sequencing. Results of the 16S rRNA gene sequence analysis showed that all screened protease-producing bacteria belonged to the class Gammaproteobacteria and most of them were affiliated with different genera within the orders Alteromonadales and Vibrionales. The N-terminal amino acid sequence analysis for fourteen extracellular proteases from fourteen screened bacterial strains revealed that all these proteases belonged to the M4 family of metalloproteases or the S8 family of serine proteases. This study presents new details on taxa of marine sedimentary protease-producing bacteria and types of their extracellular proteases, which will help to comprehensively understand the process and mechanism of the microbial enzymatic degradation of marine sedimentary organic nitrogen.

Mycoremediation of Remazol Brilliant Blue R in greywater by a novel local strain of Aspergillus iizukae 605EAN: optimisation and mechanism study

ABSTRACT The decolourisation of Remazol Brilliant Blue R (RBBR) by oxidative enzymes [Laccase (Lac), Manganese peroxidase (MnP), Lignin peroxidase (LiP)], from Aspergillus iizukae EAN605 was optimised as a function of initial substrate concentrations (30−100 mg L−1), incubation period (5–15 days) and pH (5–7). The best operating parameters to achieve the highest removal of RBBR were 57.15 mg 100 mL−1 of RBBR, pH 6 and after 8.55 days where the maximum removal was 78.34% vs. 80.00% (R 2 = 77.9%), Lac 0.22 vs. 0.28 µ mg−1, MnP 0.24 vs. 0.27 µ mg−1 and LiP 14.22 vs. 15.12 µ mg−1 of actual and predicted results, respectively. The surface analysis of A. iizukae EAN605 by field emission scanning electron microscopy suggested that the removal process takes place on the surface of the fungal mycelium cell wall as a result of the presence of Lac enzyme in the inner fungal membrane. Moreover, the phytotoxicity test confirms the absence of the dye toxicity after enzymatic degradation process which indicates the efficiency of A. iizukae EAN605 to minimise the dyes' risk to less than the toxicity level. These findings suggest that A. iizukae EAN605 has a potential for the mycoremediation of dyes in the greywater.

Synthesis, self-assembly, biodegradation and drug delivery of polyurethane copolymers from bio-based poly(1,3-propylene succinate)

A series of environmentally-friendly bio-based poly(1,3-propylene succinate) diols (bio-PPS) with different average molecular weights (Mn) were synthesized from bio-based 1,3-propanediol (bio-PDO) and bio-based succinic acid (bio-SA). With the employment of bio-PPS as a hydrophobic block and poly(ethylene glycol) (PEG) as a hydrophilic segment, the well-defined amphiphilic triblock and multi-block polyurethane (PU) copolymers with the urethane linkages between the blocks were synthesized and characterized. The chemical structures and molecular weights of these block PU copolymers were confirmed by proton nuclear magnetic resonance (1H NMR), Fourier transform infrared (FT-IR) spectrum, differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). With the Mn of bio-PPS blocks increasing from 1.40 to 8.93 kg/mol, the degree of hydrogen bonding in the PUs reduced significantly, and the glass transition temperature increased from −42.8 to −35.4 °C and from −40.1 to −33.1 °C for triblock and multi-block copolymers, respectively. Transmission electron microscopy (TEM) images revealed that both triblock and multi-block PU copolymers could spontaneously self-assemble into near-spherical core-shell micelles in aqueous solution. With the increasing bio-PPS content in the copolymers, the sizes of triblock micelles from dynamic light scattering (DLS) measurement varied from 17 to 64 nm, and the critical micelle concentration (CMC) changed from 7.22 to 0.77 mg/L. For the multi-block series, the micelle sizes increased from 24 to 71 nm and the CMC values decreased from 2.85 to 1.79 mg/L. The enzymatic degradation of the micelles for 8 weeks under the physiological environment revealed that hydrophilic PEG segments could be detached from the main chain of triblock micelles, and the degradation mainly occurred at the ester group of bio-PPS blocks in the multi-block ones. Micelles with lower bio-PPS content and multi-block architecture degraded faster during the enzymatic degradation process. A controlled release profile was observed for the doxorubicin (DOX)-loaded micelles, more than 40% and 50% DOX were released after 75 h from triblock and multi-block micelles, respectively. Moreover, the addition of lipase could accelerate the DOX release from the micelles. Cytotoxicity test proved that the PU micelles were nontoxic, while the DOX loaded micelles showed concentration-dependent cytotoxicity to HeLa cells, suggesting its potential application in the drug delivery system.

Enhanced effects of curcumin encapsulated in polycaprolactone-grafted oligocarrageenan nanomicelles, a novel nanoparticle drug delivery system

One of the most effective strategies to enhance the bioavailability and the therapeutic effect of hydrophobic drugs is the use of nanocarriers. We have used κ-carrageenan extracted from Kappaphycus alvarezii to produce oligocarrageenan via an enzymatic degradation process. Polycaprolactone (PCL) chains were grafted onto the oligocarrageenans using a protection/deprotection technique yielding polycaprolactone-grafted oligocarrageenan. The resulting amphiphilic copolymers formed spherical nanomicelles with a mean size of 187 ± 21 nm. Hydrophobic drugs such as curcumin were efficiently encapsulated in the micelles and released within 24–72 h in solution. The micelles were non-cytotoxic and facilitated the uptake of curcumin by endothelial EA-hy926 cells. They also increased the anti-inflammatory effect of curcumin in TNF-alpha-induced inflammation experiments. Finally, in vivo experiments supported a lack of toxicity in zebrafish and thus the potential use of polycaprolactone-grafted oligocarrageenan to improve the delivery of hydrophobic compounds to different organs, including liver, lung and brain as shown in mice.

Selective enzymatic degradation and porous morphology of poly(butylene succinate)/poly(lactic acid) blends

Poly(butylene succinate) (PBS) and poly(lactic acid) (PLA) were melt-blended in different proportions and selectively degraded by cutinase and proteinase K, respectively. The selective enzymatic degradation process was systematically investigated. The degraded PBS/PLA blends were analyzed via scanning electron microscopy, Fourier-transform infrared spectroscopy, powder X-ray diffraction, and differential scanning calorimetry. The results of the weight loss of PBS/PLA blends degraded by cutinase and proteinase K suggested that PLA hindered the cutinase-catalyzed degradation of PBS, whereas the addition of PBS in the blends accelerated the degradation of PLA within a specific PBS/PLA ratio. The change in crystallinity after degradation was closely related to the different way of degradation. The characterization of PBS/PLA blends after degradation showed that selective enzymatic degradation could not completely degrade PBS or PLA component. After degradation, the pores formed by proteinase K were more uniform and larger than those formed by cutinase. This work provides a new insight into the selective enzymatic degradation processes of the porous materials, which will be used in tissue engineering or oil-water separation in the future.

Direct yellow degradation by combined Fenton-enzymatic process

Abstract The removal of direct yellow 106 (DY106, C.I.40300) by a combined process of Fenton oxidation and enzymatic degradation in a sequential or mixed batch reactor is discussed. Experiments were first conducted with the enzymatic and chemical oxidation processes separately in order to determine the effects of various parameters such as pH, ferrous ion, hydrogen peroxide, dye and enzyme concentrations on the overall yield and kinetics of both processes. Decolourization was followed by UV-visible spectroscopy and high performance liquid chromatography (HPLC). Results showed that 89.5 % of DY106 were removed by enzymatic treatment after only 2 min, while 10 min of contact time were necessary to eliminate more than 98 % of 50 mg/L by Fenton’s process. A high performance was achieved under optimized conditions by the mixed combined process with time reduction down to 5 min. The study was also conducted to evaluate the efficiency of combined Fenton’s reaction as a pre-treatment and post treatment process combined with C-peroxidase at different ferrous ions concentrations. The optimal doses of Fe2+ were 2.5 mM, 1m M and 0.8 mM for Fenton, Fenton-enzymatic sequential and mixed processes. Intermediate products absorbing in UV range were detected for single Fenton or enzymatic treatment but were eliminated in all combined enzymatic-Fenton processes. Phytotoxicity tests showed that no toxicity was detected after treatment by combined process.