Microbial degradation of lignin (Enzymes, Steps, Mechanisms)


Lignin is a complex organic polymer that is found in the cell walls of most plants, especially in wood and bark. It is formed by the oxidative coupling of 4-hydroxyphenylpropanoids, which are derived from phenylalanine and tyrosine. Lignin is the most abundant aromatic biopolymer on Earth, accounting for about 30% of the organic carbon and 15-30% of the dry weight of lignocellulosic biomass .

Lignin plays a crucial role in the structure and function of plant cell walls. It provides mechanical strength, rigidity, and resistance to biotic and abiotic stresses, such as pathogens, insects, UV radiation, and water loss . Lignin also facilitates the transport of water and nutrients in the plant vascular system by making the cell walls more hydrophobic and less permeable. Lignin crosslinks with polysaccharides, such as cellulose and hemicellulose, to form a three-dimensional network that reinforces the cell wall matrix .

Lignin is also an important source of bioenergy and bioproducts. It can be converted into biofuels, such as ethanol and biodiesel, by biological or chemical processes. Lignin can also be used to produce various value-added chemicals, such as phenols, aromatics, and antioxidants . Lignin has many potential applications in various industries, such as paper, textile, pharmaceutical, cosmetic, and agricultural sectors.

However, lignin also poses some challenges for the utilization of lignocellulosic biomass. Lignin is a highly heterogeneous and recalcitrant polymer that is difficult to degrade and separate from polysaccharides . Lignin hinders the enzymatic hydrolysis of cellulose and hemicellulose into fermentable sugars, which reduces the efficiency and yield of biofuel production. Lignin also affects the quality and properties of paper and pulp products by causing coloration, brittleness, and reduced strength.

Therefore, understanding the biosynthesis, structure, and degradation of lignin is essential for improving the valorization of lignocellulosic biomass. In this blog post, we will discuss the following topics:

  • The structure of lignin
  • Microorganisms involved in lignin degradation
  • Enzymes involved in the degradation of lignin
  • Factors affecting lignin degradation
  • The process of lignin degradation
  • Mechanisms of microbial degradation of lignin
  • Example of lignin degradation by Pseudomonas