Biobleaching

Biobleaching refers to the use of biological agents to reduce coloration and remove lignin or other chromophores from plant-based materials, primarily in the pulp and paper industry and, to a lesser extent, textile processing. In pulp production, biobleaching typically involves enzymatic or fungal pretreatments that modify lignin structure or remove residual lignin, thereby lowering the chemical load required in subsequent bleaching stages.

Common enzymes include xylanases, lignin-modifying enzymes such as lignin peroxidase, manganese peroxidase, and laccase, often used in combination with mediator compounds or as part of enzyme-assisted chemical pulping. Microorganisms, especially white-rot fungi like Phanerochaete chrysosporium or Pleurotus species, can partially degrade lignin, reducing chlorine, chlorine dioxide, or hypochlorite demands in subsequent stages.

Process forms include enzyme-assisted bleaching of kraft pulps, treatment of mechanical pulps, or fungal pretreatment before chemical bleaching. In textiles, biobleaching can mean enzymatic treatment to remove natural colors or improve whiteness, using cellulases, xylanases, or laccase-based systems.

Advantages include reduced use of chlorine-based bleaching agents, lower energy consumption, and improved effluent quality with less oxidant stress. Challenges involve slower kinetics, enzyme costs, requirement for controlled conditions (pH, temperature), potential impact on fiber strength, and variability with feedstock. Industrial adoption has grown for enzyme-assisted bleaching lines but remains limited by economics and process integration.

Biobleaching research continues to optimize enzyme formulations, mediator systems, and integrated chemo-enzymatic schemes to make it competitive with conventional bleaching while meeting environmental standards.