Abstract
Lignin is a heterogeneous aromatic polymer and major component of plant cell walls. The β-O-4 alkyl aryl ether is the most abundant linkage within lignin. Given that lignin is effectively degraded on earth, as yet unknown ether bond–cleaving microorganisms could still exist in nature. In this study, we searched for microorganisms that transform 2-phenoxyacetophenone (2-PAP), a model compound for the β-O-4 linkage in lignin, by monitoring ether bond cleavage. We first isolated microorganisms that grew on medium including humic acid (soil-derived organic compound) as a carbon source. The isolated microorganisms were subsequently subjected to colorimetric assay for 2-PAP ether bond–cleaving activity; cells of the isolated strains were incubated with 2-PAP, and strains producing phenol via ether bond cleavage were selected using phenol-sensitive Gibbs reagent. This screening procedure enabled the isolation of various 2-PAP–transforming microorganisms, including 7 bacteria (genera: Acinetobacter, Cupriavidus, Nocardioides, or Streptomyces) and 1 fungus (genus: Penicillium). To our knowledge, these are the first microorganisms demonstrated to cleave the ether bond of 2-PAP. One Gram-negative bacterium, Acinetobacter sp. TUS-SO1, was characterized in detail. HPLC and GC–MS analyses revealed that strain TUS-SO1 oxidatively and selectively cleaves the ether bond of 2-PAP to produce phenol and benzoate. These results indicate that the transformation mechanism differs from that involved in reductive β-etherase, which has been well studied. Furthermore, strain TUS-SO1 efficiently transformed 2-PAP; glucose-grown TUS-SO1 cells converted 1 mM 2-PAP within only 12 h. These microorganisms might play important roles in the degradation of lignin-related compounds in nature.
Highlights
Lignin is a heterogeneous aromatic polymer and major component of plant cell walls
Screening for microorganisms that transform 2‐PAP via ether bond cleavage
We further examined the transforming activity of strain TUS-SO1 toward another commercially available Lignin model compounds (LMCs) that has a ketone group, MPHPV (Fig. S7), because this strain exhibited the activity toward the ketone compound 2-PAP but not the alcohol compound 2-PPE
Summary
Lignin is a heterogeneous aromatic polymer and major component of plant cell walls. The β-O-4 alkyl aryl ether is the most abundant linkage within lignin. The isolated microorganisms were subsequently subjected to colorimetric assay for 2-PAP ether bond– cleaving activity; cells of the isolated strains were incubated with 2-PAP, and strains producing phenol via ether bond cleavage were selected using phenol-sensitive Gibbs reagent This screening procedure enabled the isolation of various 2-PAP–transforming microorganisms, including 7 bacteria (genera: Acinetobacter, Cupriavidus, Nocardioides, or Streptomyces) and 1 fungus (genus: Penicillium). HPLC and GC–MS analyses revealed that strain TUS-SO1 oxidatively and selectively cleaves the ether bond of 2-PAP to produce phenol and benzoate These results indicate that the transformation mechanism differs from that involved in reductive β-etherase, which has been well studied. Strain TUS-SO1 efficiently transformed 2-PAP; glucose-grown TUS-SO1 cells converted 1 mM 2-PAP within only 12 h These microorganisms might play important roles in the degradation of lignin-related compounds in nature. Screening microorganisms for 2-PAP transformation capability could lead to the discovery of novel ether bond–cleaving fungi and/or bacteria
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
