Deinking of old newsprint (ONP) pulp with an engineered laccase: a greener approach for paper recycling

Rheinheimera sp. laccase was cloned and engineered to truncate domain 3 previously in our laboratory. This engineered laccase was found to deink old newsprint paper (ONP) without the need of any mediator. Response surface methodology (RSM) for statistical optimization of deinking conditions achieved deinking efficiency of 55.66% with enzyme dose of 130 U/g odp (oven-dried pulp), treatment time of 4 h and pulp consistency 5%, irrespective of the presence or absence of mediator (1-hydroxybenzotriazole; HBT). The optimized enzymatic pretreatment for deinking was validated in the R&D setup of Kuantum Papers Ltd., Hoshiarpur, Punjab (India), and an increase of 16.69, 17.18, 11.62 and 25% in brightness, breaking length, tear factor and burst factor, respectively, was achieved in addition to reducing the usage of hazardous chemicals by 50%. These results show the promising application of a greener enzymatic approach for environmentally sustainable paper recycling.