Degradation of lignin by bacteria

A novel lignin degradation bacterial consortium for efficient pulping.

One of the most notable features of strains of Acinetobacter is their ability to grow on a wide range of aromatic compounds In addition, acinetobacters isolated from natural environments can grow in simple defined mineral media with no requirement for growth factors, so they are clearly synthesising all their own aromatic amino acids and related compounds This review contains a description of the mechanisms used for the dissimilation of aromatic compounds by Acinetobacter strains; it concentrates on the best-characterised of these pathways, the mandelate pathway, but includes at least outline descriptions of the ways in which many other aromatic compounds are catabolised In addition, there is a brief summary of the pathways for the biosynthesis of aromatic amino acids and an indication of the potential competition between these pathways and those for the degradation of aromatic compounds

Metabolism of Aromatic Compounds by Acinetobacter

Publisher Summary The complex aromatic polymer lignin comprises about 25% of the land based biomass on earth, and its recycling is a vital component of the earth's carbon cycle. Its breakdown involves multiple biochemical reactions. Though the role of fungal lignin peroxidases has been well established only in recent years, bacterial lignin degradation has gained importance. Bacteria gain access to the polymer by mechanisms, such as tunnelling, erosion, and scavenging. Bacteria of several genera such as Alcaligenes, Acinetobacter, Pseudomonas, Rhizobium, Bradyrhizobium, Bacillus, and Streptomyces readily degrade numerous lignin model compounds. Acinetobacter utilized veratrylglycerol-∼-guaiacyl ether, indulin, 2-methoxy-4-formylphenoxyacetic acid, u-conidendrin and dehydrodiisoeugenol. Plasmid-mediated dissimilation of ferulic acid and guaiacolglyceryl ether has been established in Bacillus subtilis. Cloning, sequencing, and expression of the genes involved in the dissimilation of lignin substances have been done from Bacillus subtilis to improve the degradation efficiency. The most recent advances in genetic engineering are to create potential lignin-degrading bacteria and also to elucidate the molecular mechanisms involved.

Lignin degradation by bacteria

Acinetobacter sp. utilized the [ring-14C]dehydropolymer of coniferyl alcohol (DHP) (sp. act. 1.4 × 104 dpm/mg), 14C-labelled teakwood lignin (sp. act. 2.5 × 104 dpm/mg), guaiacolglyceryl ether, 2-methoxy-4-formylphenoxyacetic acid, p-benzyloxyphenol, dehydrodivanillyl alcohol, dehydrodiisoeugenol, veratrylglycerol-β-guaiacyl ether, conidendrin, black liquor lignin and indulin as sole carbon sources. The bacterium produced p-coumaric acid, p-hydroxybenzoic acid, vanillic acid, protocatechuic acid and catechol as intermediates from lignins. Acinetobacter sp. produced catechol 1,2-dioxygenase and protocatechuate 3,4-dioxygenase during the degradation of lignins.

N. Vasudevan

Papers

Degradation of 3(o-methoxyphenoxy)1,2-propanediol (guaiacol glyceryl ether) by Acinetobacter sp.