Enzymes Bleach Wood Lignin

microscopic photo of white fungus on green surface

Biological Strategy

Aspergillus niger

AskNature Team

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Chemically Break Down Polymers

The vast majority of biochemical assembly and breakdown processes–even by the most complex organisms–occur within cells. In fact, cells are able to perform hundreds, even thousands of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). For example, one of the biochemical pathways that break down proteins into their constituent amino acids is the protease enzyme-catalyzed processes that occur within the confined space of the lysosome–a membrane bound organelle in eukaryotic cells.

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Fungi

Kingdom Fungi: Mildews, molds, mushrooms, rusts, smuts, and yeasts

Once thought to be more closely related to plants, fungi have been found to contain chitin in their cell walls, indicating a closer evolutionary relationship to animals. Fungi are decomposers, using digestive enzymes to break down their surroundings, making them an essential part of ecosystems worldwide, as new soil is formed from rotting matter. Almost all fungi reproduce through spores (mushrooms, molds) or asexual budding (some yeast). There are estimated to be more than 2 million species, but only about 140,000 have been described. Fungi have great importance in culture, food, and medicine (including being the source of penicillin) worldwide.

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Enzymes produced by a marine fungus found on mangroves can "bleach" wood pulp by catalyzing the break down of lignin.

A fungus that calls mangrove forests home produces enzymes that can degrade lignin, a complex compound that helps give plants their structural strength and resiliency. This tough chemical compound is also difficult to degrade which poses a problem for the paper industry since lignin is a major contributor to the brown color of unbleached pulp. Strong oxidizing agents, particularly chlorine bleach, have traditionally been used to break down lignin to produce white paper, but this process generates toxic chlorinated compounds as waste products. Fungal enzymes not only break down lignin without generating toxic byproducts, they do not attack fibers needed to produce strong paper products.