Fungal Biodegradative Oxidants in Lignocellulose: Fluorescence Mapping and Correlation With Gene Expression

Hammel, Kenneth E.¹  Ralph, John¹  Hunt, Christopher G.²  Houtman, Carl J.² 

[1] Univ. of Wisconsin, Madison, WI (United States);U.S. Forest Products Lab., Madison, WI (United States)

关键词: Lignocellulose;    Lignin Degradation;    Carbon Cycling;    Biofuels;    White Rot Fungus;    Brown Rot Fungus;    Soft Rot Fungus;   

DOI  :  10.2172/1319808
RP-ID  :  DOE-UWISC--06929
PID  :  OSTI ID: 1319808

美国|英语

来源: SciTech Connect

【 摘 要 】

This work focused on new methods for the detection of oxidation in natural substrates during the deconstruction of lignocellulose by microoganisms. Oxidation was the focus because all known biological systems that degrade lignin are oxidative. The detection methods involved the used of (a) micrometer-scale beads carrying a fluorescent dye that is sensitive to oxidation, (b) 13C-labeled synthetic lignins whose breakdown products can be assessed using mass spectrometry and nuclear magnetic resonance spectroscopy, and (c) a fluorometric stain that is highly sensitive to incipient oxidation during microbial attack. The results showed (a) that one white rot fungus, Phanerochaete chrysosporium, produces diffusible oxidants on wood, and that the onset of oxidation is coincident with the marked up-regulation of genes that encode ligninolytic peroxidases and auxiliary oxidative enzymes; (b) that a more selectively ligninolytic white rot fungus, Ceriporiopsis subvermispora, produces a highly diastereoselective oxidative system for attack on lignin; (c) that a brown rot fungus, Serpula lacrymans, uses extracellular hydroquinone metabolites to drive the production of lignocellulose-oxidizing free radicals; (d) that both white rot and brown rot fungi produce highly diffusible mild oxidants that modify lignocellulose at the earliest stage of substrate deconstruction; and (e) that lignin degradation in a tropical soil is not inhibited as much as expected during periods of flooding-induced hypoxia, which indicates that unknown mechanisms for attack on lignin remain to be discovered.