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.

With an annual production of more than 400 million tons, paper is the main product of the largest biorefinery process industrially implemented. Enzymes have been used for pulp refining to dramatically reduce energy consumption. However, exact mechanisms related to the individual enzymes are hardly understood. Yet, this knowledge would be important to predict enzyme performance in industrial processes. Three commercial refining enzyme formulations showed different endoglucanase (1.25 nkat mg−1–13.7 nkat mg−1), β-glucosidase (0.57 nkat mg−1–1.34 nkat mg−1) and xylanase activities (1.78 nkat ml−1–62.1 nkat mg−1) on model substrates. Additionally, distinct amounts of reducing sugars from hardwood sulfate pulp were released. Endoglucases were purified from each formulation by using hydrophobic interaction and anion exchange chromatography and showed molecular weights from 20 to 55 kDa and specific activities ranging between 3.11 and 26.3 nkat mg−1 according to endoglucanase specific derivatized cellopentaose (CellG5). Refining trials of hardwood sulfate pulp were conducted using a PFI laboratory mill and fiber properties such as degree of refining or fiber length and properties of formed sheets like tensile index were monitored. Thereby, enzymes were dosed based on identical endoglucanase activity on CellG5. Enzyme formulations and purified endoglucanases led to an increase of the degree of refining of up to 47.9 [°SR] at 6000 PFI revolutions while the tensile index was improved by up to 76.0 Nm g−1. In summary, refining effects can be primarily attributed to endoglucanases indicating activity on CellG5 being a suitable parameter for enzyme dosing.

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.

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