In Europe, most of the discarded and un-wearable textiles are incinerated or landfilled. In this study, we present an enzyme-based strategy for the recovery of valuable building blocks from mixed textile waste and blends as a circular economy concept. Therefore, model and real textile waste were sequentially incubated with (1) protease for the extraction of amino acids from wool components (95% efficiency) and (2) cellulases for the recovery of glucose from cotton and rayon constituents (85% efficiency). The purity of the remaining poly(ethylene terephthalate) (PET) unaltered by the enzymatic treatments was assessed via Fourier-transformed infrared spectroscopy. Amino acids recovered from wool were characterized via elementary and molecular size analysis, while the glucose resulting from the cotton hydrolysis was successfully converted into ethanol by fermentation with Saccharomyces cerevisiae. This work demonstrated that the step-wise application of enzymes can be used for the recovery of pure building blocks (glucose) and their further reuse in fermentative processes.

Among synthetic thermoplastic fiber materials for reinforcement, high modulus and low shrinkage poly(ethylene terephthalate) (HMLS-PET) became the major carcass material for the low-to medium-end tire segment. Usually cords are coated with a resorcinol−formaldehyde−latex (RFL) dip to achieve acceptable power transmission. However, the low concentration of polar groups on the PET's surface requires an additional activation with costly and potentially toxic chemicals to create additional nucleophilic groups prior to RFL dipping. Here, a green enzyme based alternative to chemical HMLS-PET activation was investigated. Four different cutinase variants from Thermobif ida cellulosilytica were shown to hydrolyze HMLS-PET cords, creating new carboxylic and hydroxyl groups with distinct exoendo-wise selectivity. The highest degree of enzymatic functionalization reached a concentration of 0.51 nmol mm −2 of COOH with a release of 1.35 mM of soluble products after 72 h. The chemical treatment with 1 M NaOH released more soluble products leading up to a 10% decrease of the tensile strength while the functionalization degree achieved was only 0.21 nmol mm −2 . This clearly indicates a more endowise mode of hydrolysis for the enzymatic treatment when compared to chemical hydrolysis. Scanning electron microscopy of the fibers confirmed the aggressiveness of the chemical treatment, whereas the enzymatic approach only led to 0.7% solubilization of the polymer with no loss of mechanical properties and crystallinity changes. The newly created groups were chemically accessible and reactive in the dipping step and led after the vulcanization to a significant improvement of the adhesion between the polymer and a representative carcass rubber compound according to the peel tests.

Viscose (also known as Rayon) filaments are obtained from regenerated cellulose and are used in many different sectors mainly as reinforcement material in tires and other cord applications and in the clothing industry. The incorporation of a phosphor-containing pigment imparts flame-retardancy properties to these fibers, which then can be used as part of personal protection textiles delivering wear comfort. There are no recycling strategies for these materials being brought to landfills or chemically degraded since incineration is difficult because of their flame retardancy. In this study, an enzyme-based strategy for the recovery of glucose and of the phosphor pigment without altering their chemical structures was developed as a circular economy solution. Rayon fibers were completely hydrolyzed by a cellulase preparation while 98% of the glucose (reducing sugar assay and HPLC analysis) and more than 99% of the flame-retardant pigment present in the fibers was recovered. The recovered pigment was analyzed via 1H, 13C, and 31P NMR, and the purity >95% was comparable to that of the commercially available pigment. The recovered glucose was successfully used as carbon source for ethanol production by Saccharomyces cerevisiae while the recycled phosphor pigment was reused in viscose filament production leading to similar mechanical properties like those measured for virgin fibers. This work presents an environmentally friendly recycling strategy of functional rayon fibers for the recovery of the two major components, namely, glucose and the pigment.

Poly(ethylene terephthalate) (PET) and nylon find their main applications in working clothes, domestic furniture and as indoor decoration (curtains and carpets). The increasing attention on healthy lifestyle, together with protection and safety, gained a strong interest in today's society. In this context, reducing the flammability of textiles has been tackled by designing flame retardants (FRs) able to suppress or delay the flame propagation. Commercially available FRs for textiles often consist of brominated, chlorinated and organo-phosphorus compounds, which are considered a great concern for human health and for the environment. In this study, Deoxyribose Nucleic Acid (DNA) was investigated as a green and eco-friendly alternative to halogen-containing FRs. DNA is in fact able to provide flame retardant properties due to its intrinsically intumescent building blocks (deoxyribose, phosphoric-polyphosphoric acid, and nitrogen-containing bases). In a first step, anchor groups (i.e., carboxyl groups) for subsequent coupling of DNA were introduced to PET and nylon-6 fabrics via limited surface hydrolysis with Humicola insolens cutinase (HiC). Released monomer/oligomers were measured via HPLC (1 mM of BHET for PET and 0.07 mM of caprolactam from nylon after 72 h). In a next step, DNA immobilization on the activated polymers was studied by using three different coupling systems, namely: EDC/NHS, dopamine, and tyrosine. DNA coupling was confirmed via FT-IR that showed typical bands at 1,220, 970, and 840 cm−1. The tyrosine/DNA coupling on nylon fabrics resulted to be the most effective as certified by the lowest burning rate and total burning time (35 s, 150 mm, and 4.3 mm*s−1 for the blank and 3.5 s, 17.5 mm, and 5 mm* s−1 for nylon/tyrosine/DNA) which was also confirmed by FT-IR and ESEM/EDS measurements. Thermogravimetric analysis (TGA) further confirmed that tyrosine/DNA coated nylon showed a lower thermal degradation between 450 and 625°C when compared to the untreated samples.

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Side streams from modern lignocellulose biorefineries have found value-added applications in various industries ranging from food to medical. Here, bioproduction of glutathione from glucose recovered from man-made cellulose fiber production was investigated. Rayon fibers were enzymatically hydrolyzed and the resulting glucose and Zn in the hydrolysate were successfully used for glutathione (15.5 mg L À1 ) production by an engineered strain of Saccharomyces cerevisiae. Next, out of reduced glutathione (GSH) in combination with human serum albumin (HSA) and silk fibroin (SF), nanocapsules were developed. Production of HSA/SF/GSH nanocapsules was further optimized by experimental design and the resulting nanocapsules were characterized by particle size, zeta potential, chemical properties (secondary structure ratios, crosslinking, and release kinetics) and thermal stability. An average hydrodynamic radius of 462.72 AE 73.36 nm and average zeta potential of À13.67 AE 0.01 mV were obtained by optimization using an experimental design approach. Increasing secondary structure ratios for HSA/SF/GSH nanocapsules indicated the successful integration of GSH into the nanocapsule shell by ultrasound induced selfassembly. Regarding possible future application as a cosmeceutical, flavor substances were encapsulated, and the release kinetics of flavor substances were studied, resulting in pH-and viscosity-dependent maximum release rates of 40.45 AE 0.35% for menthol and 38.60 AE 2.07% for raspberry ketone. Additionally, the radical scavenging properties of the system were evaluated, showing increased scavenging for produced HSA/SF/GSH nanocapsules compared to controls. Therefore, HSA/SF/GSH nanocapsules are seen as a promising new system in cosmeceutical approaches. † Electronic supplementary information (ESI) available: Details regarding the structure of the flame retardant pigment, detailed information on the used HPLC gradients, detailed information of the experimental designs DoE 1 and 2 including the corresponding results (ANOVA tables, response contour plots, coefficient plots), ATR-FTIR spectra and the correlated secondary structure ratios, chemical structures of the flavor substances, results of DLS based temperature stability analysis and information of artificial saliva viscosities. See