Self-sufficient redox biotransformation of lignin-related benzoic acids with <i>Aspergillus flavus</i>

Palazzolo, Martín A.; Mascotti, María Laura; Lewkowicz, Elizabeth Sandra; Kurina-Sanz, Marcela

doi:10.1007/s10295-015-1696-4

Cited by 8 publications

(2 citation statements)

References 34 publications

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“…Oxidized and reduced quinones have been found ubiquitously in dissolved organic matter in environmental samples [ 42 ]. Oxidative decarboxylation of lignin-related benzoic acids by Aspergillus flavus [ 43 ] and by Pycnoporus cinnabarinus [ 44 ] has also been reported.…”

Section: Discussionmentioning

confidence: 99%

Redox processes acidify and decarboxylate steam-pretreated lignocellulosic biomass and are modulated by LPMO and catalase

Peciulyte

Samuelsson

Olsson

et al. 2018

Biotechnol Biofuels

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BackgroundThe bioconversion of lignocellulosic feedstocks to ethanol is being commercialised, but further process development is required to improve their economic feasibility. Efficient saccharification of lignocellulose to fermentable sugars requires oxidative cleavage of glycosidic linkages by lytic polysaccharide monooxygenases (LPMOs). However, a proper understanding of the catalytic mechanism of this enzyme class and the interaction with other redox processes associated with the saccharification of lignocellulose is still lacking. The in-use stability of LPMO-containing enzyme cocktails is increased by the addition of catalase implying that hydrogen peroxide (H2O2) is generated in the slurry during incubation. Therefore, we sought to characterize the effects of enzymatic and abiotic sources of H2O2 on lignocellulose hydrolysis to identify parameters that could improve this process. Moreover, we studied the abiotic redox reactions of steam-pretreated wheat straw as a function of temperature and dry-matter (DM) content.ResultsAbiotic reactions in pretreated wheat straw consume oxygen, release carbon dioxide (CO2) to the slurry, and decrease the pH. The magnitude of these reactions increased with temperature and with DM content. The presence of LPMO during saccharification reduced the amount of CO2 liberated, while the effect on pH was insignificant. Catalase led to increased decarboxylation through an unknown mechanism. Both in situ-generated and added H2O2 caused a decrease in pH.ConclusionsAbiotic redox processes similar to those that occur in natural water-logged environments also affect the saccharification of pretreated lignocellulose. Heating of the lignocellulosic material and adjustment of pH trigger rapid oxygen consumption and acidification of the slurry. In industrial settings, it will be of utmost importance to control these processes. LPMOs interact with the surrounding redox compounds and redirect abiotic electron flow from decarboxylating reactions to fuel the oxidative cleavage of glycosidic bonds in cellulose.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1159-z) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Redox processes acidify and decarboxylate steam-pretreated lignocellulosic biomass and are modulated by LPMO and catalase

Peciulyte

Samuelsson

Olsson

et al. 2018

Biotechnol Biofuels

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“…Pathway 3 was observed by overexpressing Acar of N. iowensis in E. coli resulting in the conversion of benzoic acid to benzaldehyde and further to benzyl alcohol by endogenous enzymes (Kunjapur et al, 2014). The formation of benzyl alcohol was also observed in Aspergillus flavus when it was grown on benzoic acid (Palazzolo et al, 2015), indicating that this pathway is also present in nature. Pathway 4a has been described in several Bacilli and Paenibacillus sp.…”

Section: Benzoic Acid P-hydroxybenzoic Acid and Related Metabolic Pamentioning

confidence: 99%

A comparison between the homocyclic aromatic metabolic pathways from plant-derived compounds by bacteria and fungi

Lubbers

Dilokpimol

Visser

et al. 2019

Biotechnology Advances

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Aromatic compounds derived from lignin are of great interest for renewable biotechnical applications. They can serve in many industries e.g. as biochemical building blocks for bioplastics or biofuels, or as antioxidants, flavor agents or food preservatives. In nature, lignin is degraded by microorganisms, which results in the release of homocyclic aromatic compounds. Homocyclic aromatic compounds can also be linked to polysaccharides, tannins and even found freely in plant biomass. As these compounds are often toxic to microbes already at low concentrations, they need to be degraded or converted to less toxic forms. Prior to ring cleavage, the plant-and lignin-derived aromatic compounds are converted to seven central ring-fission intermediates, i.e. catechol, protocatechuic acid, hydroxyquinol, hydroquinone, gentisic acid, gallic acid and pyrogallol through complex aromatic metabolic pathways and used as energy source in the tricarboxylic acid cycle. Over the decades, bacterial aromatic metabolism has been described in great detail. However, the studies on fungal aromatic pathways are scattered over different pathways and species, complicating a comprehensive view of fungal aromatic metabolism. In this review, we depicted the similarities and differences of the reported aromatic metabolic pathways in fungi and bacteria. Although both microorganisms share the main conversion routes, many alternative pathways are observed in fungi. Understanding the microbial aromatic metabolic pathways could lead to metabolic engineering for strain improvement and promote valorization of lignin and related aromatic compounds.

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Selective Enzymatic Transformation to Aldehydes in vivo by Fungal Carboxylate Reductase from Neurospora crassa

et al. 2016

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The enzymatic reduction of carboxylic acids is in its infancy with only a handful of biocatalysts available to this end. We have increased the spectrum of carboxylate‐reducing enzymes (CARs) with the sequence of a fungal CAR from Neurospora crassa OR74A (NcCAR). NcCAR was efficiently expressed in E. coli using an autoinduction protocol at low temperature. It was purified and characterized in vitro, revealing a broad substrate acceptance, a pH optimum at pH 5.5–6.0, a T m of 45 °C and inhibition by the co‐product pyrophosphate which can be alleviated by the addition of pyrophosphatase. The synthetic utility of NcCAR was demonstrated in a whole‐cell biotransformation using the Escherichia coli K‐12 MG1655 RARE strain in order to suppress overreduction to undesired alcohol. The fragrance compound piperonal was prepared from piperonylic acid (30 mM) on gram scale in 92 % isolated yield in >98% purity. This corresponds to a productivity of 1.5 g/L/h.

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Self-sufficient redox biotransformation of lignin-related benzoic acids with Aspergillus flavus

Cited by 8 publications

References 34 publications

Redox processes acidify and decarboxylate steam-pretreated lignocellulosic biomass and are modulated by LPMO and catalase

Redox processes acidify and decarboxylate steam-pretreated lignocellulosic biomass and are modulated by LPMO and catalase

A comparison between the homocyclic aromatic metabolic pathways from plant-derived compounds by bacteria and fungi

Selective Enzymatic Transformation to Aldehydes in vivo by Fungal Carboxylate Reductase from Neurospora crassa

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