Selective oxidation of uronic acids into aldaric acids over gold catalyst

Rautiainen, Sari; Lehtinen, Petra; Chen, Jingjing; Vehkamäki, Marko; Niemelä, Klaus; Leskelä, Markku; Repo, Timo

doi:10.1039/c5ra01802a

Cited by 28 publications

(27 citation statements)

References 43 publications

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“…Several pectin rich waste biomass streams, such as residues from citrus fruit and sugar beet processing are available and currently poorly utilized. Galactaric acid can be produced from d -galUA via chemical oxidation [5], however an attractive alternative is the engineering of a microorganism to perform this reaction.…”

Section: Introductionmentioning

confidence: 99%

Engineering Aspergillus niger for galactaric acid production: elimination of galactaric acid catabolism by using RNA sequencing and CRISPR/Cas9

2016

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Background meso-Galactaric acid is a dicarboxylic acid that can be produced by the oxidation of d-galacturonic acid, the main constituent of pectin. Mould strains can be engineered to perform this oxidation by expressing the bacterial enzyme uronate dehydrogenase. In addition, the endogenous pathway for d-galacturonic acid catabolism has to be inactivated. The filamentous fungus Aspergillus niger would be a suitable strain for galactaric acid production since it is efficient in pectin hydrolysis, however, it is catabolizing the resulting galactaric acid via an unknown catabolic pathway.ResultsIn this study, a transcriptomics approach was used to identify genes involved in galactaric acid catabolism. Several genes were deleted using CRISPR/Cas9 together with in vitro synthesized sgRNA. As a result, galactaric acid catabolism was disrupted. An engineered A. niger strain combining the disrupted galactaric and d-galacturonic acid catabolism with an expression of a heterologous uronate dehydrogenase produced galactaric acid from d-galacturonic acid. The resulting strain was also converting pectin-rich biomass to galactaric acid in a consolidated bioprocess.ConclusionsIn the present study, we demonstrated the use of CRISPR/Cas9 mediated gene deletion technology in A. niger in an metabolic engineering application. As a result, a strain for the efficient production of galactaric acid from d-galacturonic acid was generated. The present study highlights the usefulness of CRISPR/Cas9 technology in the metabolic engineering of filamentous fungi.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0613-5) contains supplementary material, which is available to authorized users.

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Section: Introductionmentioning

confidence: 99%

Engineering Aspergillus niger for galactaric acid production: elimination of galactaric acid catabolism by using RNA sequencing and CRISPR/Cas9

2016

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“…Previously, we reported oxidation of benzyl alcohol [15] and carbohydrates [18] using Au/Al 2 O 3 catalyst prepared by direct-ion exchange method (DIE), and the same catalyst was used herein to oxidize vanillin. In addition, gold was deposited on alumina and titania using deposition-precipitation with urea (DPU).…”

Section: Resultsmentioning

confidence: 99%

“…We reported the preparation and characterization of Au/Al 2 O 3 -DIE previously in Ref. [18]. Gold was supported on alumina and titania using deposition-precipitation method with urea as precipitation agent, adapted from [19].…”

Section: Catalyst Synthesismentioning

confidence: 99%

Oxidation of Vanillin with Supported Gold Nanoparticles

et al. 2016

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The selective oxidation of vanillin to vanillic acid was achieved using gold nanoparticles supported on alumina and titania. Selectivities up to 99 % at conversions over 90 % were obtained with pressurized oxygen as green oxidant in alkaline aqueous media. Our studies showed that the addition of at least 2 equivalents of strong Brönsted base had a crucial role in suppressing vanillin degradation and achieving high selectivity and conversion. The highest activities involved turn-over frequency values up to 1300 h -1 and were achieved using alumina supported catalysts.

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“…The conversion of UA to AA such as galactaric (GA) or glucaric acid (GlcA) is traditionally carried out via HNO 3 ‐catalyzed oxidation, with the process usually limited by the yield and by the hazards associated with the use of concentrated strong acid . Alternatives to this process are gold‐catalyzed aqueous catalytic oxidation of AA under alkaline or base‐free conditions, both providing efficient and highly selective reactions …”

Section: Methodsmentioning

confidence: 99%

“…The LMS‐catalyzed oxidation of GalA in acid environment using a laccase, represents the first example of an in vitro enzymatic conversion of uronic acid into an aldaric derivate in very mild conditions (30 °C; pH 3) with the simultaneous GA precipitation, therefore allowing an easy and inexpensive recovery of the reaction product (Figure ). So far, this process has been done using acids and metals while the here presented process represents a sustainable way of avoiding this using a fully biocatalyzed approach at mild conditions …”

Section: Methodsmentioning

confidence: 99%

Sustainable Galactarate‐Based Polymers: Multi‐Enzymatic Production of Pectin‐Derived Polyesters

Vastano

Pellis

Machado

et al. 2019

Macromol. Rapid Commun.

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Large amounts of agricultural wastes are rich in pectins that, in many cases, disrupt the processing of food residues due to gelation. Despite pectins being a promising sustainable feedstock for bio‐based chemical production, the current pathways to produce platform molecules from this polysaccharide are hazardous and entail the use of strong acids. The present work describes a sequence of biocatalyzed reactions that involves 1) the extraction of pectin from sugar beet pulp and enzymatic recovery of galacturonic acid (GalA), followed by 2) the enzymatic oxidation of the GalA aldehyde and the recovery of galactaric acid (GA), and 3) the biocatalyzed polycondensation of GA to obtain fully bio‐based polyesters carrying lateral hydroxy functionalities. The acid‐free pectin extraction is optimized using enzymes and microwave technology. The conditions for enzymatic oxidation of GalA allow the separation of the GA produced by a simple centrifugation step that leads to the enzyme‐catalyzed polycondensation reactions.

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Selective oxidation of uronic acids into aldaric acids over gold catalyst

Abstract: Uronic acids available from hemicelluloses were oxidized into aldaric acids, valuable building block chemicals. Au/Al2O3 oxidized glucuronic and galacturonic acids quantitatively to the corresponding glucaric and galactaric acids at mild conditions.

Cited by 28 publications

References 43 publications

Engineering Aspergillus niger for galactaric acid production: elimination of galactaric acid catabolism by using RNA sequencing and CRISPR/Cas9

Engineering Aspergillus niger for galactaric acid production: elimination of galactaric acid catabolism by using RNA sequencing and CRISPR/Cas9

Oxidation of Vanillin with Supported Gold Nanoparticles

Sustainable Galactarate‐Based Polymers: Multi‐Enzymatic Production of Pectin‐Derived Polyesters

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