Biodegradation
Biodegradation of lignin would lead to destruction of wooden goods, especially buildings. However biodegradation of lignin is a prerequisite for processing biofuel from plant raw materials. Current processing setups show some problematic residuals after processing the digestible or degradable contents. The improving of lignin degradation would drive the output from biofuel processing to better gain or better efficiency factor.
Lignin is indigestible by animal enzymes, but some fungi (such as the Dryad's saddle) and bacteria are able to secrete ligninases (also named lignases) that can biodegrade the polymer. The details of the biodegradation are not yet well understood. The pathway depends on the type of wood decay - in fungi either brown rot, soft rot, or white rot. The enzymes involved may employ free radicals for depolymerization reactions. Well understood lignolytic enzymes are manganese peroxidase, lignin peroxidase and cellobiose dehydrogenase. Furthermore, because of its cross-linking with the other cell wall components, it minimizes the accessibility of cellulose and hemicellulose to microbial enzymes. Hence, in general lignin is associated with reduced digestibility of the overall plant biomass, which helps defend against pathogens and pests.
Lignin degradation is made by micro-organisms like fungi and bacteria. Lignin peroxidase (also "ligninase", EC number 1.14.99) is a hemoprotein from the white-rot fungus Phanerochaete chrysosporium with a variety of lignin-degrading reactions, all dependent on hydrogen peroxide to incorporate molecular oxygen into reaction products. There are also several other microbial enzymes that are believed to be involved in lignin biodegradation, such as manganese peroxidase, laccase, and Cellobiose dehydrogenase (acceptor).
Lignin-related chemicals can be further processed by bacteria. For instance, the aerobic Gram-negative soil bacterium Sphingomonas paucimobilis is able to degrade lignin-related biphenyl chemical compounds.
Read more about this topic: Lignin