Production optimization scale-up and application of a multifunctional enzyme cocktail for eco-friendly pulp biobleaching.

In the paper industry, pulp bleaching is an essential step to increase the whiteness and brightness of paper, which is typically achieved using chlorine-based or oxidative chemicals that cause significant environmental pollution. In the present study, Bacillus tequilensis LXM 55 produced a cocktail of lignocellulolytic and hemicellulolytic enzymes. Solid-state fermentation (SSF) is a cost-effective and efficient method suitable for large-scale enzyme production. Therefore, the SSF process was optimized for the production of the enzyme cocktail employing traditional and statistical methods. Optimization resulted in a significant improvement in enzyme yields, with 34.0-, 22.85-, and 20.37-fold increases in enzyme yield for laccase (L) (4518.54 IU g⁻¹), xylanase (X) (2664.81 IU g⁻¹), and mannanase (M) (1448.42 IU g⁻¹), respectively. For commercial viability, the optimized process was successfully scaled up to a 1 kg substrate level without any significant loss in enzyme productivity. The enzyme cocktail (L+X+M) was applied to pulp bleaching, resulting in a 48% reduction in kappa number and a 12.1% improvement in brightness. Most significantly, the enzymatic pre-treatment of pulp led to a 40% reduction in chlorine usage while achieving the same brightness and whiteness as pulp treated with the traditional chemical-based process. These findings demonstrate the potential of the enzyme cocktail as an efficient, eco-friendly, and industrially scalable alternative for sustainable pulp bleaching in the paper industry.