Biodegradation of deep eutectic solvent pre-treated natural rubber gloves by Klebsiella aerogenes: A sustainable approach to rubber waste management

Abstract

This study investigates the potential of deep eutectic solvents (DES) to enhance the biodegradation of natural rubber gloves (NRG) by Klebsiella aerogenes. Choline chloride and urea (ChCl: urea) was the DES employed to pre-treat NRG at various temperatures (80°C to 140°C) and durations (0.5 h to 5 h). Pre-treated rubber (p-NRG) underwent significant physical and chemical changes, enhancing its biodegradability. Analytical techniques such as dry weight analysis, bacteria cell concentration, FTIR TGA, and SEM were used to characterize the pre-treated and biodegraded samples. The results have demonstrated a significant weight loss and structural modifications in p-NRG, with the highest degradation of 43 % observed at 140°C for 5 hours of pretreatment before biodegradation. Meanwhile, merely 17 % of weight loss was observed when pre-treatment was not employed. DES pre-treatment notably enhanced NRG biodegradability, achieving a 50.6 % weight loss when biodegradation was conducted at pH 7 and 35°C. The highest cell concentration, 0.75 g/L, was recorded in the second week of the biodegradation process. Results have indicated that the maximum protein concentration of 697.3 µg/ml, along with the highest enzyme activities for laccase and manganese peroxidase (MnP) at 0.46 ± 0.05 IU and 0.30 ± 0.05 IU respectively, were recorded in the second week of the biodegradation process. DES pre-treatment has significantly improved the biodegradability of NRG by Klebsiella aerogenes, offering a promising and eco-friendly solution for rubber waste management.