Elena Orgilés-Calpena

While various methodologies have been used to evaluate leather biodegradability, limited data exist regarding their respective strengths, limitations and complementarity, especially for finished leathers produced using chrome-free tanning systems. Consequently, this work assesses the biodegradation of eight commercial eco-friendly tanned finished leathers (phenolic-, zeolite-, aluminium- and titanium-based treatments) using two standardised laboratory approaches, ISO 14855-1:2012 (controlled composting) and ISO 20136:2020 (liquid-phase biodegradation), together with physicochemical characterisation and phytotoxicity/ecotoxicity endpoints. The results showed that biodegradation generally occurred faster under ISO 20136:2020 conditions, mainly because this assay uses ground leather shavings and an aqueous, well-mixed medium, whereas ISO 14855-1:2012 evaluates mineralisation of larger leather pieces in a compost matrix. Phenolic- and titanium-tanned leathers showed consistently high biodegradation in both assays, whereas the aluminium-tanned leather biodegraded efficiently under ISO 14855-1:2012 but showed limited biodegradation under ISO 20136:2020, highlighting that assay conditions can reveal constraints related to the complete material architecture, collagen stabilisation, effective accessibility and method-specific exposure conditions rather than to a single leaching mechanism. Phytotoxicity and ecotoxicity assessments indicated low environmental impact of the degradation products under the tested conditions. Overall, the combined use of both standards provides a more comprehensive and industrially useful framework for assessing the end-of-life behaviour of finished leathers than either method alone.

Inefficient chromium (III)–collagen cross-linking during leather tanning generates solid waste and effluents containing residual chromium, raising environmental and health concerns. Biological strategies are increasingly popular for tannery waste treatment, but the microbial communities involved in leather degradation remain poorly understood. This study did not seek to evaluate leather disintegration according to standardised compostability criteria, but to establish a thermophilic composting system suitable for characterising leather-associated microbial communities, biofilm formation on leather and isolating cultivable strains. Composting assays were carried out at two scales, in which wet blue leather was mixed with organic compost under self-heating thermophilic conditions. Temperature was monitored, and mass loss and changes in leather structure were determined by gravimetry and scanning electron microscopy. Bacterial and fungal communities in compost with and without leather were analysed using high-throughput amplicon sequencing. Thermophilic consortia dominated by Firmicutes, Actinobacteria and Ascomycota were established, and several bacterial isolates and a filamentous fungus were recovered. Together, these results provide a first basis for understanding the communities and strains associated with chromium-tanned leather during thermophilic composting, supporting future searches for microorganisms and enzymes of interest for biological strategies to manage chromium-tanned leather waste.

Chromium-tanned leather waste presents a significant environmental challenge due to its resistance to microbial degradation and potential to release toxic chromium compounds. This study aimed to evaluate the biodegradability of wet blue leather through thermo-philic composting without the addition of exogenous microorganisms, and to characterise the associated microbial communities. Composting trials were conducted in 2 L and 40 L Dewar vessels under controlled thermophilic conditions. Gravimetric analysis, scanning electron microscopy (SEM), high-throughput sequencing, and microbial culturing were applied. The small-scale system achieved a 38.94% mass loss, whereas the large-scale composting resulted in the complete disintegration of leather into fragments smaller than 1 cm after approximately 40 days. Metagenomic analysis revealed distinct microbial communities in leather compost, enriched with genera such as Sinibacillus, Bdellovibrio, and Thermomyces, which are known for their thermotolerant enzymatic activity. SEM images confirmed bacterial colonisation and biofilm formation on the leather surface. Cultivable strains with metal tolerance and proteolytic potential were also isolated. These findings demonstrate that composting under thermophilic conditions can effectively degrade chromium-tanned leather. The study also provides a basis for the development of targeted microbial treatments or biotechnological strategies to reduce the environmental impact of the leather industry and support circular bioeconomy approaches in waste management.

Leather biodegradation is a complex microbial process with increasing relevance for sustainable waste management. In this study, we investigated bacterial communities responsible for the degradation of leather treated with different tanning agents (chrome, Zeolite, Biole^®) using high-throughput 16S rRNA gene sequencing and metatranscriptomic analysis. Proteobacteria, Bacteroidetes, and Patescibacteria emerged as the dominant phyla, while genera such as Acinetobacter, Pseudomonas, and Sphingopyxis were identified as key contributors to enzymatic activity and potential metal resistance. A total of 1302 enzymes were expressed across all the conditions, including 46 proteases, with endopeptidase La, endopeptidase Clp, and methionyl aminopeptidase being the most abundant. Collagen samples exhibited the highest functional diversity and total enzyme expression, whereas chrome-treated samples showed elevated protease activity, indicating selective pressure from heavy metals. Differential enzyme expression patterns were linked to both the microbial identity and tanning chemistry, revealing genus- and treatment-specific enzymatic signatures. These findings deepen our understanding of how tanning agents modulate the microbial structure and function and identify proteases with potential applications in the bioremediation and eco-innovation of leather waste processing.

The quest for sustainable and efficient methods for extracting cellulose nanocrystals (CNCs) remains critical in the development of advanced materials. This study refines the acid hydrolysis process for cellulose derived from rice straw, an abundant agricultural waste, focusing on the relationship between hydrolysis parameters and CNC properties. The research identifies conditions that enhance crystallinity and colloidal stability while effectively transforming amorphous cellulose into nanocrystals. Advanced characterization techniques, including XRD, SEM, TEM, and zeta potential measurements, provided insights into the structural and colloidal properties of CNCs. The findings demonstrate the influence of reaction temperature, time, and acid concentration on CNC quality, with optimized conditions yielding nanocrystals with enhanced stability and well-defined morphology. This study underscores the potential of rice straw as a renewable resource, advancing the circular economy by promoting the use of sustainable materials in high-value applications such as composite reinforcement and coatings.

Leather biodegradation is a microbially driven process of increasing interest for the development of sustainable waste management strategies. In this study, bacterial communities involved in the biodegradation of leather tanned with different agents (chrome, zeolite, Biole®) were characterised using high-throughput sequencing. Taxonomic profiling based on 16S rRNA gene amplification revealed that Proteobacteria, Bacteroidetes, and Patescibacteria were the dominant phyla across samples. Functional analysis, carried out through metatranscriptomic sequencing of RNA molecules, identified a total of 1,302 expressed enzymes, of which 46 were classified as proteases. The most abundant proteases included Endopeptidase La, Endopeptidase Clp, and Methionyl aminopeptidase. Although collagen samples exhibited the lowest bacterial diversity, they showed the highest total enzyme expression, whereas chrome-treated samples displayed increased protease activity, indicating selective pressure associated with heavy metal content. Additionally, distinct functional enzyme sets were found to be either shared among or exclusive to specific tanning treatments. Genera such as Acinetobacter, Pseudomonas, and Sphingopyxis were identified as key contributors to enzymatic activity and potential metal resistance. These results provide new insights into how tanning agents shape microbial communities and their enzymatic functions, highlighting specific taxa and enzymes with potential applications in the bioremediation of leather waste and environmentally friendly processing technologies.

This paper focuses on investigating the use of low-pressure oxygen plasma as a surface treatment aimed at enhancing the wettability and dyeability of cotton fabrics for use in textiles and footwear materials. Plasma activation modified the cotton fabric surfaces, increasing their affinity for polar liquids. The research thoroughly characterised the treated fabrics through a combination of analytical methods and physical testing. Plasma treatment was performed using a 13.56 MHz RF generator at 90 W power, with an oxygen flow rate of 500 sccm and a pressure of 0.30 mbar, for treatment durations of 30, 60, and 120 s. Changes in surface chemistry were analysed with XPS, while SEM was used to observe morphological changes. Static water contact angle measurements confirmed a reduction from 128.5° in untreated cotton to 25.6° in samples treated for 30 s, indicating a significant increase in hydrophilicity. Water absorption tests showed a maximum absorption capacity of 119.6% after 60 min for plasma-treated samples, compared to 65.7% for untreated cotton. Contact angle measurements verified that surface hydrophilicity increased following the treatment. Furthermore, physical tests, such as rub fastness, colourimetry, and water absorption, were carried out to evaluate improvements in wettability, dyeability, and overall performance. The results showed notable enhancements in the wetting properties of cotton textiles, enabling better absorption of water and dyes, along with improved fixation. The comprehensive characterisations provided insights into the mechanisms behind these improvements. This research offers a sustainable approach for the textile industry, as plasma technology is a dry process that enhances dyeing efficiency while maintaining fabric performance and lowering environmental impact.

This study aimed to enhance the initial adhesion performance of reactive polyurethane hot-melt adhesives by using a bio-based polycarbonate polyol instead of traditional polyester or polyether polyols and by incorporating thermoplastic polyurethane (TPU) in varied proportions. Adhesives synthesized from bio-based polycarbonate polyols and polypropylene glycol with MDI as the isocyanate were characterized chemically, thermally, and mechanically (FTIR, DSC, plate–plate rheology, DMA, and T-peel strength test). Adding 10–15 wt.% TPU significantly improved green strength and initial adhesion at room temperature and after accelerated cooling. The bio-based polycarbonate polyol promotes superior flexibility at low temperatures compared to fossil-derived alternatives, aligning with sustainability objectives. The results showed that 10 wt.% TPU maximized green strength without compromising flexibility, whereas 15 wt.% TPU, though enhancing adhesion, reduced flexibility due to increased crystallinity. T-peel tests on footwear materials indicated that all the adhesives exceeded the EN 15307:2015 requirements, with the highest peel strength achieved after curing. These findings highlight the benefit of bio-based polycarbonate polyols and TPUs in achieving strong, flexible, and eco-friendly adhesives suitable for demanding applications.

The increasing concern for sustainability in the footwear industry has spurred the exploration of eco-friendly alternatives for materials commonly used in sole manufacturing. This study examined the effect of incorporating rice straw and cellulose as fillers into soles made from either styrene–butadiene rubber (SBR) or thermoplastic polyurethane (TPU). Both fillers were used as a substitute in mass percentages ranging from 5 to 20% in the original SBR and TPU formulas, and their impact on mechanical properties such as abrasion and tear resistance, as well as thermal properties, was thoroughly evaluated. The results demonstrated that the inclusion of fillers affects the overall performance of the soles, with the optimal balance of mechanical and thermal properties observed at a 10% filler content. At this level, improvements in durability were achieved without significantly compromising flexibility or abrasion resistance. Thermal analysis revealed increased thermal stability at moderate filler contents. This research not only offers a sustainable alternative to traditional materials but also enhances sole performance by improving the composition. Furthermore, this study paves the way for future research on the feasibility of incorporating eco-friendly materials into other consumer product applications, highlighting a commitment to innovation and sustainability in product design.