Catalytic Efficiency of some Mediators in Laccase-Catalyzed Alcohol Oxidation

Barreca, Anna Maria; Sjögren, Birger; Fabbrini, Maura; Galli, Carlo; Gentili, Patrizia

doi:10.1080/10242420410001692750

Cited by 33 publications

(30 citation statements)

References 17 publications

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“…3). Laccasemediated oxidation of non-phenolic lignin units can follow an electron transfer, a radical hydrogen atom transfer, or an ionic mechanism, depending on the mediator (Barreca et al, 2004). Several organic and inorganic compounds, such as thiol and phenol aromatic derivatives, N-hydroxy compounds and ferrocyanide, have been reported as effective mediators for the above-mentioned purposes (Susana and José, 2006).…”

Section: Laccasementioning

confidence: 97%

Bacteria and lignin degradation

Yuan

Yang

2008

Front. Biol. China

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Lignin is both the most abundant aromatic (phenolic) polymer and the second most abundant raw material. It is degraded and modified by bacteria in the natural world, and bacteria seem to play a leading role in decomposing lignin in aquatic ecosystems. Lignin-degrading bacteria approach the polymer by mechanisms such as tunneling, erosion, and cavitation. With the advantages of immense environmental adaptability and biochemical versatility, bacteria deserve to be studied for their ligninolytic potential.

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Section: Laccasementioning

confidence: 97%

Bacteria and lignin degradation

Yuan

Yang

2008

Front. Biol. China

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“…Since laccases are oxidized by molecular oxygen, which acts as the final electron acceptor,25, 26 laccase‐based bleaching can be considered as an enzyme‐catalyzed oxygen delignification stage. However, the high redox potential of the activated copper species at the enzyme catalytic site enables a strong delignification of pulp, which is mediated by the stable radicals formed during enzyme oxidation of suitable chemical mediators 27, 28…”

Section: Introductionmentioning

confidence: 99%

Integrating laccase–mediator treatment into an industrial‐type sequence for totally chlorine‐free bleaching of eucalypt kraft pulp

Ibarra

Camarero

Romero

et al. 2006

J of Chemical Tech & Biotech

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Enzymatic delignification using the high-redox potential thermostable laccase from the fungus Pycnoporus cinnabarinus and a chemical mediator (1-hydroxybenzotriazole) was investigated to improve totally chlorine-free (TCF) bleaching of Eucalyptus globulus kraft pulps. Different points of incorporation of the enzyme treatment into an industrial-type bleaching sequence (consisting of double oxygen, chelation and peroxide stages) were investigated in pressurized laboratory reactors. The best final pulp properties were obtained using an O-O-L-Q-PoP sequence, where a laccase-mediator stage (L) was incorporated between double oxygen and chelation. The worse results, when the enzymatic and chelation treatments were combined in a unique stage, seemed related to partial inhibition of laccase-mediator activity by the chelator. The new TCF sequence including the laccase stage permitted to improve eucalypt pulp delignification to values around kappa 5 (hexenuronic acid contribution over 50%) compared to kappa 7 using only TCF chemical reagents. In a similar way, the final brightness obtained, over 91% ISO, was 3-4 points higher than that obtained in the chemical sequences. Although technical and economic issues are to be solved, the results obtained show the feasibility of integrating a laccase-mediator treatment into a TCF sequence for bleaching eucalypt kraft pulp.

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“…As expected, there was a very poor correlation between the log(P) values of the mediators and the distribution coefficients, since the oxidised mediators present in these experiments are radical cations. 4,5,54 In addition, there may be structure-specific, non-covalent interactions between the oxidized mediators and the ionic liquids, which would further complicate prediction of extraction efficiencies.…”

Section: Distribution Coefficients Of Mediators Between Ionic Liquidsmentioning

confidence: 99%