Role of various bacterial enzymes in complete depolymerization of lignin: A review

Abstract

Abstract Lignin is the second abundant biomass (10–35%) which is associated with cellulose and hemicellulose in plant cellwall. It has complex aromatic structure and high molecular weight which makes it resistant as well as difficult to degrade by microorganisms. Although, white-rot fungi has high capability of lignin depolymerization by producing array of enzymes; but they are not applicable in actual industrial conditions. In comparison to fungi, bacteria can tolerate wider pH, temperature, oxygen ranges and are easy to genetically manipulate. The bacterial ligninolytic enzymes can be divided in following major category: lignin modifying enzymes (LME) i.e. lignin peroxidase, manganese peroxidase, dye decolorizing peroxidase, laccase (phenol oxidase) and lignin-degrading auxillary enzymes (LDA) i.e. β-aryl ether, biphenyl, phenyl coumarane, ferulate degrading enzymes, superoxide dismutase, catalase peroxidase. LDA enzymes assist core lignin degrading enzymes and degrade a dimer or monomer after depolymerization of lignin macromolecule. These enzymes have broad applications in bioremediation of textile, pulp industry waste water, aromatic compounds and in production of bioplastic etc. Therefore, this review article summarize significant research on the bacterial sources, production conditions, enzyme characteristics, mechanism and structure, industrial applications as well as role of cutting edge “multi omics” and “synthetic biology” techniques for improved lignin degradation have also been discussed.