An Economical Industrially Feasible Approach for Denim Biobleaching: Reusing of Laccase and Mediator for Multiple Cycles.

In the present study, an economical and commercially viable process has been standardized using a novel strategy of recycling the mediator and reusing the enzyme for multiple cycles of denim bleaching. Bacillus cabrialesii SJ2 produced an extracellular laccase active/ stable in a wide range of temperature (40-70 °C) and pH (6-9). The enzyme yield was significantly enhanced with a 154-fold increase (2216.5 IUml-1) under the optimized conditions. The enzyme efficiently degraded indigo carmine within 30 and 45 min at 50 °C/8.5 pH with and without a laccase-mediator, respectively. Enzyme was able to bleach denim without any mediator; however, effective bleaching was achieved in the presence of ABTS as a mediator. To make the process economical, the cost of the reaction was reduced by recycling the mediator and adding a reduced dose of enzyme for multiple bleaching cycles. In recycling studies, the same bleaching effect on fabric was maintained for up to eight cycles with the same mediator in the reaction mixture (500 µM ABTS) and the addition of reduced doses of the enzyme (10 IU in the first cycle and 5 IU in subsequent cycles). The mechanical properties of the enzymatically bleached fabric, elongation (7.6 mm), tensile strength (1105 N) and color fastness were comparable to those of the unbleached fabric and superior to the chemically bleached samples. This study represents the first report of standardizing a process by recycling the mediator and the enzyme for denim biobleaching, making it an economically viable and a practical alternative for industrial application. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-024-01418-z.