Isolation and characterization of microorganisms capable of cleaving the ether bond of 2-phenoxyacetophenone

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.

Bacterioplankton Communities in Dissolved Organic Carbon-Rich Amazonian Black Water

“… Methylobacterium could also profit from by-products of the humic degradation; methanol, one of the main carbon sources for methylotrophic bacteria like Methylobacterium ( 59 ), is produced during the demethylation of humic substances ( 60 ). Several studies have documented the humic substances degradation potential of Acinetobacter ( 61 , 62 ). The set of genes detected in this genus suggests that the humic compounds’ O -demethylation ( 63 ) and ring cleavage ( 64 ) differ from those of Polynucleobacter and Methylobacterium (see more details in the supplemental material under “Pathways of humic compounds’ degradation”).…”

Isolation and characterization of filamentous fungi capable of degrading the mycotoxin patulin

“…Reaction products were analyzed by HPLC using an LC‐20 system (Shimadzu, Kyoto, Japan) equipped with a Cosmosil 5C18‐PAQ packed column (4.6 × 250 mm, Nacalai Tesque, Kyoto, Japan) (Kawana et al, 2022; Oya et al, 2022). The post‐reaction mixture (200 μL) was acidified by the addition of HCl (pH 2–3), and methanol (300 μL) was then added.…”

Stability and Reactivity of Guaiacylglycerol-β-Guaiacyl Ether, a Compound Modeling β-O-4 Linkage in Lignin

“…As for the biodegradation occurring in aqueous media under ambient conditions, the impact of pH and blank mineral medium has not been assessed. To the best of our knowledge, only two studies evaluated the biodegradation of lignin model compounds, both claiming significant Gβ2 conversion rates [12,17], although without detailed quantitative data [12]. The impact of biodegradation was evaluated in this study using three different strains.…”