A circular economy approach to leather by products valorization towards a zero-waste process

Introduction: The tanning industry has a significant waste production and is a major contributor to environmental pollution; The adoption of circular economy principles will help repurposing by-products with a focus on reutilizing leather remnants; With this approach, the objective is to minimize environmental damage and effectively manage waste; This will contribute to sustainability with a reduction of overall waste and will align with UN sustainability goal 12 (Ensure sustainable consumption and production patterns) through the re-use of by products. Objectives: Exploration of different enzymes and conditions to enhance leather industry hydrolysis process to achieve a more sustainable and circular approach; Creation of versatile functional coatings within the leather industry; Utilization of commercial enzyme (Protabate P) and alternative enzymes (Bromelain and Alcalase) to validate its use; Valorization of protein-rich leather by-products. Conclusion: Protabate P 10% 24 h had higher hydrolysis degree (49.66%) and higher total protein (55103.43 μg protein/mL) than all the other enzymes. Regarding antioxidant activity, Alcalase 10% 24 h showed higher values (39.32 μM Trolox equivalents/mL). Apart from total protein, Bromelain 10% 24 h showed the lowest values for hydrolysis degree and antioxidant activity. Between time 0 and pre-final, molecules with MW <0.2 kDa consistently have a higher area. Conducting an enzyme inactivation (2 h/90 ºC) might result in molecule aggregation, leading to an increase in molecules with MW exceeding 50 kDa. Re-using leather byproducts can help the tanning industry to reduce the waste and achieve the UN sustainability goal nr 12. This study outlines the potential of re-using leather by-products to create versatile functional coatings through a circular and more sustainable process.