Enzymatic deinking of used-paper using laccase and cellulase from Metarhizium granulomatis and Aspergillus niger: a sustainable upcycling approach

The pulp and paper industry is one of the main pillars of the global economy. The average global paper upcycling rate is 60%, with < 30% paper upcycling rate in India. The present investigation focuses the exploration of enzymatic deinking technology (EDT) for the upcycling of used-paper (photocopied/print) using laccase and cellulase enzymes, produced from fungal isolates. Among all the isolated strains, Metarhizium granulomatis and Aspergillus niger showed maximum enzyme activity for laccase (196.786 U/mL) and cellulase (8.471 U/mL), respectively. Gene-specific analysis and protein profiling approach revealed the presence of genes (β-tubulin, eglB, and cbh) responsible for the respective enzyme production. A comparative analysis for paper upcycling between the experimental set (enzyme extract, commercial cellulase, and chemical treatment) revealed an enhancement in the optical/physical properties of upcycled paper (enzyme extract treated). Microbial cellulase achieved the highest deinking efficiency (95.29%) as compared to others. Current novel technology can be deployed for upcycling of used-paper having potential for revitalizing paper upcycling industry globally.