Degradation of sulfide linkages between isoprenes by lipid peroxidation catalyzed by manganese peroxidase.
Scission of sulfide linkages in vulcanized rubber has been a major concern since the early 20th century, because devulcanization is a key process for recycling waste rubber products as polymer materials that pose low environmental risks. We herein demonstrate that lipid peroxidation (LPO) of linoleic acid by manganese peroxidase (MnP), a proposed lignin-degradation system in the early stage of selective white rot fungi, cleaves sulfide bond in a model rubber compound, di(2-methylpent-2-enyl) sulfide, to 2,4-dimethylthiophene and 2-methyl-2-pentenal. The major intermediate of the LPO process, 2,4-decadienal was directly oxidized by MnP to cleave the sulfur-carbon bond. We propose that electrophilic radicals from 2,4-decadienal abstract one electron from a sulfur atom of the model compound to produce the sulfur radical cation intermediate, which in turn reacts with molecular oxygen to cleave the sulfur-carbon bond. The discovery of free radical-mediated scission of sulfide bond coupled with Mn oxidation provides a novel strategy for recycling vulcanized rubber wastes.
Sato
Shin
S
Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji Kyoto 611-0011, Japan.
Ohashi
Yasunori
Y
Kojima
Masaaki
M
Watanabe
Takahito
T
Honda
Yoichi
Y
Watanabe
Takashi
T
D001673:Biodegradation, Environmental; D002070:Butadienes / Q000737:chemistry / Q000378:metabolism*; D002384:Catalysis; D045782:Hemiterpenes / Q000737:chemistry / Q000378:metabolism*; D015227:Lipid Peroxidation; D010420:Pentanes / Q000737:chemistry / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D012408:Rubber / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry*
D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D013440:Sulfides; C005059:isoprene; D012408:Rubber; D010544:Peroxidases; C051129:manganese peroxidase