Leiotrametes flavida MTCC 12927 laccase: scaleup, purification and its application for dye decolourisation enhanced by water-soluble mediator TEMPOL.

Laccase production from an isolated white rot fungus identified as Leiotrametes flavida MTCC 12927 was optimised in flasks, scaled up in 5 and 10 L working volume fermenters and purified to homogeneity. Purified laccase was tested for its decolourisation potential on 3 dyes: Basic Red 46 (azo class), Acid Blue 9 (triarylmethane class) and Reactive Blue 21 (phthalocyanine class). TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl), a less expensive water-soluble hydroxy derivative of mediator TEMPO (2,2,6,6-tetramethylpiperidin-1-yl) oxidanyl), was tested as a mediator which had not been reported before to our knowledge along with well-known mediators hydroxybenzotriazole (HBT) and syringaldehyde (SYD). Laccase in the presence of HBT could decolourise all the 3 dyes. Basic Red 46 and Acid Blue 9 were completely decolourised in 4 and 8 h, respectively. Reactive Blue 21 showed a decolourisation of 70.3% compared to 50.3% with TEMPOL and 20% with the enzyme alone. Laccase + TEMPOL combination was significantly better than HBT in decolourising azo dye Basic Red 46 completely within 30 min compared to 4 h for HBT. Furthermore, laccase TEMPOL and HBT combinations were also tested in azo dye-containing tannery effluent. TEMPOL showed a higher decolourisation rate of 36% compared to 22% for the latter. Chemical oxygen demand (COD) analysis of treated effluent samples showed a COD reduction of 23.2% for laccase + TEMPOL treatment and 19.2% for laccase + HBT compared to 7.8% with laccase alone. TEMPOL showed potential as a low-cost, water-soluble mediator for azo dye decolourisation.

Supplementary information: The online version contains supplementary material available at 10.1007/s13205-025-04259-9.