| 1. |
- Aevarsson, Arnthór, et al.
(author)
-
Going to extremes - a metagenomic journey into the dark matter of life
- 2021
-
In: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968. ; 368:12
-
Research review (peer-reviewed)abstract
- The Virus-X-Viral Metagenomics for Innovation Value-project was a scientific expedition to explore and exploit uncharted territory of genetic diversity in extreme natural environments such as geothermal hot springs and deep-sea ocean ecosystems. Specifically, the project was set to analyse and exploit viral metagenomes with the ultimate goal of developing new gene products with high innovation value for applications in biotechnology, pharmaceutical, medical, and the life science sectors. Viral gene pool analysis is also essential to obtain fundamental insight into ecosystem dynamics and to investigate how viruses influence the evolution of microbes and multicellular organisms. The Virus-X Consortium, established in 2016, included experts from eight European countries. The unique approach based on high throughput bioinformatics technologies combined with structural and functional studies resulted in the development of a biodiscovery pipeline of significant capacity and scale. The activities within the Virus-X consortium cover the entire range from bioprospecting and methods development in bioinformatics to protein production and characterisation, with the final goal of translating our results into new products for the bioeconomy. The significant impact the consortium made in all of these areas was possible due to the successful cooperation between expert teams that worked together to solve a complex scientific problem using state-of-the-art technologies as well as developing novel tools to explore the virosphere, widely considered as the last great frontier of life.
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| 2. |
- Ahlqvist, Josefin, et al.
(author)
-
Crystal structure and initial characterization of a novel archaeal-like Holliday junction-resolving enzyme from Thermus thermophilus phage Tth15-6
- 2022
-
In: Acta crystallographica. Section D, Structural biology. - 2059-7983. ; 78:Pt 2, s. 212-227
-
Journal article (peer-reviewed)abstract
- This study describes the production, characterization and structure determination of a novel Holliday junction-resolving enzyme. The enzyme, termed Hjc_15-6, is encoded in the genome of phage Tth15-6, which infects Thermus thermophilus. Hjc_15-6 was heterologously produced in Escherichia coli and high yields of soluble and biologically active recombinant enzyme were obtained in both complex and defined media. Amino-acid sequence and structure comparison suggested that the enzyme belongs to a group of enzymes classified as archaeal Holliday junction-resolving enzymes, which are typically divalent metal ion-binding dimers that are able to cleave X-shaped dsDNA-Holliday junctions (Hjs). The crystal structure of Hjc_15-6 was determined to 2.5 Å resolution using the selenomethionine single-wavelength anomalous dispersion method. To our knowledge, this is the first crystal structure of an Hj-resolving enzyme originating from a bacteriophage that can be classified as an archaeal type of Hj-resolving enzyme. As such, it represents a new fold for Hj-resolving enzymes from phages. Characterization of the structure of Hjc_15-6 suggests that it may form a dimer, or even a homodimer of dimers, and activity studies show endonuclease activity towards Hjs. Furthermore, based on sequence analysis it is proposed that Hjc_15-6 has a three-part catalytic motif corresponding to E-SD-EVK, and this motif may be common among other Hj-resolving enzymes originating from thermophilic bacteriophages.
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| 3. |
- Ahlqvist, Josefin, et al.
(author)
-
Crystal structure of DNA polymerase I from Thermus phage G20c
- 2022
-
In: Acta crystallographica. Section D, Structural biology. - 2059-7983. ; 78:Pt 11, s. 1384-1398
-
Journal article (peer-reviewed)abstract
- This study describes the structure of DNA polymerase I from Thermus phage G20c, termed PolI_G20c. This is the first structure of a DNA polymerase originating from a group of related thermophilic bacteriophages infecting Thermus thermophilus, including phages G20c, TSP4, P74-26, P23-45 and phiFA and the novel phage Tth15-6. Sequence and structural analysis of PolI_G20c revealed a 3'-5' exonuclease domain and a DNA polymerase domain, and activity screening confirmed that both domains were functional. No functional 5'-3' exonuclease domain was present. Structural analysis also revealed a novel specific structure motif, here termed SβαR, that was not previously identified in any polymerase belonging to the DNA polymerases I (or the DNA polymerase A family). The SβαR motif did not show any homology to the sequences or structures of known DNA polymerases. The exception was the sequence conservation of the residues in this motif in putative DNA polymerases encoded in the genomes of a group of thermophilic phages related to Thermus phage G20c. The structure of PolI_G20c was determined with the aid of another structure that was determined in parallel and was used as a model for molecular replacement. This other structure was of a 3'-5' exonuclease termed ExnV1. The cloned and expressed gene encoding ExnV1 was isolated from a thermophilic virus metagenome that was collected from several hot springs in Iceland. The structure of ExnV1, which contains the novel SβαR motif, was first determined to 2.19 Å resolution. With these data at hand, the structure of PolI_G20c was determined to 2.97 Å resolution. The structures of PolI_G20c and ExnV1 are most similar to those of the Klenow fragment of DNA polymerase I (PDB entry 2kzz) from Escherichia coli, DNA polymerase I from Geobacillus stearothermophilus (PDB entry 1knc) and Taq polymerase (PDB entry 1bgx) from Thermus aquaticus.
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| 4. |
- Ara, Kazi Zubaida Gulshan, et al.
(author)
-
Characterization and diversity of the complete set of GH family 3 enzymes from Rhodothermus marinus DSM 4253
- 2020
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10
-
Journal article (peer-reviewed)abstract
- The genome of Rhodothermus marinus DSM 4253 encodes six glycoside hydrolases (GH) classified under GH family 3 (GH3): RmBgl3A, RmBgl3B, RmBgl3C, RmXyl3A, RmXyl3B and RmNag3. The biochemical function, modelled 3D-structure, gene cluster and evolutionary relationships of each of these enzymes were studied. The six enzymes were clustered into three major evolutionary lineages of GH3: β-N-acetyl-glucosaminidases, β-1,4-glucosidases/β-xylosidases and macrolide β-glucosidases. The RmNag3 with additional β-lactamase domain clustered with the deepest rooted GH3-lineage of β-N-acetyl-glucosaminidases and was active on acetyl-chitooligosaccharides. RmBgl3B displayed β-1,4-glucosidase activity and was the only representative of the lineage clustered with macrolide β-glucosidases from Actinomycetes. The β-xylosidases, RmXyl3A and RmXyl3B, and the β-glucosidases RmBgl3A and RmBgl3C clustered within the major β-glucosidases/β-xylosidases evolutionary lineage. RmXyl3A and RmXyl3B showed β-xylosidase activity with different specificities for para-nitrophenyl (pNP)-linked substrates and xylooligosaccharides. RmBgl3A displayed β-1,4-glucosidase/β-xylosidase activity while RmBgl3C was active on pNP-β-Glc and β-1,3-1,4-linked glucosyl disaccharides. Putative polysaccharide utilization gene clusters were also investigated for both R. marinus DSM 4253 and DSM 4252T (homolog strain). The analysis showed that in the homolog strain DSM 4252T Rmar_1080 (RmXyl3A) and Rmar_1081 (RmXyl3B) are parts of a putative polysaccharide utilization locus (PUL) for xylan utilization.
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| 5. |
- Birgisson, Hakon, et al.
(author)
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Immobilization of a recombinant Escherichia coli producing a thermostable alpha-L-rhamnosidase: Creation of a bioreactor for hydrolyses of naringin
- 2007
-
In: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 40:5, s. 1181-1187
-
Journal article (peer-reviewed)abstract
- An U-L-rhamnosidase (E.C. 3.2.1.40) from a newly discovered thermophilic bacterium was expressed in Escherichia coli BL21 DE3 pRIL cells. The cells were immobilized in Ca2+-alginate beads. The temperature of 50 degrees C used in reactions, appeared to be sufficient for making the mesophilic strain porous enough for the substrate to access the cloned thermostable enzyme. Pretreatment of cells with heat or lysozyme prior to bead formation did not improve the results. The best cell concentration (w/w) for bead preparation was found to be 0.0 192 g ml(-1) and stability of beads increased if CaCl2 concentration in buffers and substrate was kept at 50 mM. In a 60 min assay, the optimal pH of the entrapped cells was found to be 7.8 and the optimal temperature 60 degrees C. By packing the beads in a column, a bioreactor for production Of L-rhamnose from naringin was created. Full degradation of 7.9 mM naringin could be reached by running the reactor at 1 ml min(-1) at 50 degrees C. The optimal running temperature of the reactor was found to be 50 degrees C and the reactor was fully stable over 3 days at that temperature. On the fourth day, substrate degradation capacity had decreased by 10-15%. (c) 2006 Elsevier Inc. All rights reserved.
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| 6. |
- Daugbjerg Christensen, Monica, et al.
(author)
-
Cloning and Characterization of a Novel N-Acetyl-D-galactosamine-4-O-sulfate Sulfatase, SulA1, from a Marine Arthrobacter Strain
- 2024
-
In: Marine Drugs. - 1660-3397. ; 22:3
-
Journal article (peer-reviewed)abstract
- Sulfation is gaining increased interest due to the role of sulfate in the bioactivity of many polysaccharides of marine origin. Hence, sulfatases, enzymes that control the degree of sulfation, are being more extensively researched. In this work, a novel sulfatase (SulA1) encoded by the gene sulA1 was characterized. The sulA1-gene is located upstream of a chondroitin lyase encoding gene in the genome of the marine Arthrobacter strain (MAT3885). The sulfatase was produced in Escherichia coli. Based on the primary sequence, the enzyme is classified under sulfatase family 1 and the two catalytic residues typical of the sulfatase 1 family—Cys57 (post-translationally modified to formyl glycine for function) and His190—were conserved. The enzyme showed increased activity, but not improved stability, in the presence of Ca2+, and conserved residues for Ca2+ binding were identified (Asp17, Asp18, Asp277, and Asn278) in a structural model of the enzyme. The temperature and pH activity profiles (screened using p-nitrocatechol sulfate) were narrow, with an activity optimum at 40–50 °C and a pH optimum at pH 5.5. The Tm was significantly higher (67 °C) than the activity optimum. Desulfation activity was not detected on polymeric substrates, but was found on GalNAc4S, which is a sulfated monomer in the repeated disaccharide unit (GlcA–GalNAc4S) of, e.g., chondroitin sulfate A. The position of the sulA1 gene upstream of a chondroitin lyase gene and combined with the activity on GalNAc4S suggests that there is an involvement of the enzyme in the chondroitin-degrading cascade reaction, which specifically removes sulfate from monomeric GalNAc4S from chondroitin sulfate degradation products.
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| 7. |
- Hreggvidsson, Gudmundur O, et al.
(author)
-
Biocatalytic refining of polysaccharides from brown seaweeds
- 2020. - 1
-
In: Sustainable Seaweed Technologies : Cultivation, Biorefinery and Applications - Cultivation, Biorefinery and Applications. - 9780128179437 - 9780128179444 ; , s. 447-504
-
Book chapter (peer-reviewed)abstract
- Brown macroalgae constitute 40% of the global production of seaweed, corresponding to approximately 10 million tonnes annually. Traditionally, seaweeds have been the source of hydrocolloids, food, and feed products. Due to possibilities for large-scale farming, brown macroalgae are a biomass with considerable potential for increased utilization. The main constituent polysaccharides, being alginate, cellulose, laminaran, and fucoidan, are the components of greatest importance for biorefinery usage. The polysaccharides can be extracted and applied for their physical or bioactive properties or used as a carbon source for microbial conversions to biofuels and commodity chemicals. The structural complexity and heterogeneous sugar composition of the polysaccharides make them a challenging biorefinery feedstock. These challenges can be overcome by the increasingly innovative biocatalytic tools, enzymes and microbes, that are being developed and that can be expected to open new opportunities and expand the product portfolio. However, there are still knowledge gaps, and further understanding is required on the molecular level of these interesting polymers, the tools, the refining possibilities, as well as transforming this knowledge to innovations—processes and products.
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| 8. |
- Kristjansdottir, Thordis, et al.
(author)
-
Engineering the carotenoid biosynthetic pathway in Rhodothermus marinus for lycopene production
- 2020
-
In: Metabolic Engineering Communications. - : Elsevier BV. - 2214-0301. ; 11
-
Journal article (peer-reviewed)abstract
- Rhodothermus marinus has the potential to be well suited for biorefineries, as an aerobic thermophile that produces thermostable enzymes and is able to utilize polysaccharides from different 2nd and 3rd generation biomass. The bacterium produces valuable chemicals such as carotenoids. However, the native carotenoids are not established for industrial production and R. marinus needs to be genetically modified to produce higher value carotenoids. Here we genetically modified the carotenoid biosynthetic gene cluster resulting in three different mutants, most importantly the lycopene producing mutant TK-3 (ΔtrpBΔpurAΔcruFcrtB::trpBcrtBT.thermophilus). The genetic modifications and subsequent structural analysis of carotenoids helped clarify the carotenoid biosynthetic pathway in R. marinus. The nucleotide sequences encoding the enzymes phytoene synthase (CrtB) and the previously unidentified 1′,2′-hydratase (CruF) were found fused together and encoded by a single gene in R. marinus. Deleting only the cruF part of the gene did not result in an active CrtB enzyme. However, by deleting the entire gene and inserting the crtB gene from Thermus thermophilus, a mutant strain was obtained, producing lycopene as the sole carotenoid. The lycopene produced by TK-3 was quantified as 0.49 g/kg CDW (cell dry weight).
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| 9. |
- Lange, Lene, et al.
(author)
-
Opportunities for Seaweed Biorefinery
- 2020. - 1
-
In: Sustainable Seaweed Technologies : Cultivation, Biorefinery and Application - Cultivation, Biorefinery and Application. - 9780128179444 - 9780128179437 ; , s. 3-31
-
Book chapter (peer-reviewed)abstract
- This introductory chapter provides an overview of seaweed biorefinery opportunities, providing basis for multiple value chains, contributing to nutrition and health of a growing global population, to local job generation and development, to ecosystem services, and not the least to climate change mitigation and adaptation. A unique and rich diversity of the seaweed components provides the basis for the broad spectrum of value-chains described here. Red, brown, and green seaweeds are phylogenetically very different and this is reflected in their differences in growth, structure, and biochemical composition. Stable supply and high quality of feedstock are essential for unlocking the value-adding potential of seaweeds. A special focus of the chapter is to provide an overview of the range of different methods of seaweed production (through cultivation or from natural growth, collected or cut at the shore). Furthermore, the results of dedicated efforts to develop new deep-sea cultivation technologies of brown seaweed are highlighted. The chapter has a dual message with regard to seaweed processing: the need to develop more environmentally benign biological processing (to replace chemical processing); the advantage (regarding resource efficiency) and opportunities (social and economic) of designing seaweed biorefineries according to the cascading principle. Making optimized use of all valuable components of seaweed biomass, cascading from high-value products, such as skin care, health-promoting food and feed supplements and functional food ingredients; to lower-value products, such as plant stimulants, soil improvers, and bioenergy. Lastly, this introductory chapter provides global perspectives for future development of sustainable seaweed utilization, contributing to the UN-SDGs, providing livelihood and health for more.
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| 10. |
- Linares-Pastén, Javier A., et al.
(author)
-
Modeled 3D-Structures of Proteobacterial Transglycosylases from Glycoside Hydrolase Family 17 Give Insight in Ligand Interactions Explaining Differences in Transglycosylation Products
- 2021
-
In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 11:9
-
Journal article (peer-reviewed)abstract
- The structures of glycoside hydrolase family 17 (GH17) catalytic modules from modular proteins in the ndvB loci in Pseudomonas aeruginosa (Glt1), P. putida (Glt3) and Bradyrhizobium diazoefficiens (previously B. japonicum) (Glt20) were modeled to shed light on reported differences between these homologous transglycosylases concerning substrate size, preferred cleavage site (from reducing end (Glt20: DP2 product) or non-reducing end (Glt1, Glt3: DP4 products)), branching (Glt20) and linkage formed (1,3-linkage in Glt1, Glt3 and 1,6-linkage in Glt20). Hybrid models were built and stability of the resulting TIM-barrel structures was supported by molecular dynamics simulations. Catalytic amino acids were identified by superimposition of GH17 structures, and function was verified by mutagenesis using Glt20 as template (i.e., E120 and E209). Ligand docking revealed six putative subsites (−4, −3, −2, −1, +1 and +2), and the conserved interacting residues suggest substrate binding in the same orientation in all three transglycosylases, despite release of the donor oligosaccharide product from either the reducing (Glt20) or non-reducing end (Glt1, Gl3). Subsites +1 and +2 are most conserved and the difference in release is likely due to changes in loop structures, leading to loss of hydrogen bonds in Glt20. Substrate docking in Glt20 indicate that presence of covalently bound donor in glycone subsites −4 to −1 creates space to accommodate acceptor oligosaccharide in alternative subsites in the catalytic cleft, promoting a branching point and formation of a 1,6-linkage. The minimum donor size of DP5, can be explained assuming preferred binding of DP4 substrates in subsite −4 to −1, preventing catalysis.
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| 11. |
- Mukti, Israt Jahan, et al.
(author)
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Medium development and production of carotenoids and exopolysaccharides by the extremophile Rhodothermus marinus DSM16675 in glucose-based defined media
- 2022
-
In: Microbial Cell Factories. - : Springer Science and Business Media LLC. - 1475-2859. ; 21
-
Journal article (peer-reviewed)abstract
- Background: The marine thermophilic bacterium Rhodothermus marinus can degrade many polysaccharides which makes it interesting as a future cell factory. Progress using this bacterium has, however, been hampered by limited knowledge on media and conditions for biomass production, often resulting in low cell yields and low productivity, highlighting the need to develop conditions that allow studies of the microbe on molecular level. This study presents development of defined conditions that support growth, combined with evaluation of production of carotenoids and exopolysaccharides (EPSs) by R. marinus strain DSM 16675.Results: Two defined media were initially prepared: one including a low addition of yeast extract (modified Wolfe’s medium) and one based on specific components (defined medium base, DMB) to which two amino acids (N and Q), were added. Cultivation trials of R. marinus DSM 16675 in shake flasks, resulted in maximum cell densities (OD620 nm) of 2.36 ± 0.057, cell dry weight (CDW) 1.2 ± 0.14 mg/L, total carotenoids 0.59 × 10–3 mg/L, and EPSs 1.72 ± 0.03 mg/L using 2 g/L glucose in DMB. In Wolfe’s medium (supplemented by 0.05 g/L yeast extract and 2.5 g/L glucose), maximum OD620 nm was 2.07 ± 0.05, CDW 1.05 ± 0.07 mg/L, total carotenoids 0.39 × 10–3 mg/L, and EPSs 1.74 ± 0.2 mg/L. Growth trials at 5 g/L glucose in these media either failed or resulted in incomplete substrate utilization. To improve reproducibility and increase substrate utilization, a screening of macroelements (e.g. phosphate) in DMB, was combined with use of trace elements and vitamins of the modified Wolfe’s medium. The resulting defined minimal R. marinus medium, (DRM), allowed reproducible cultivations to a final OD620nm of 6.6 ± 0.05, CDW 2.85 ± 0.07 mg/L, a maximum specific growth rate (µmax) of 0.26 h−1, total carotenoids 0.77 × 10–3 mg/L and EPSs 3.4 ± 0.17 mg/L in cultivations supplemented with up to 5 g/L glucose.Conclusion: A minimal defined medium (DRM) was designed that resulted in reproducible growth and an almost doubled formation of both total carotenoids and EPSs. Such defined conditions, are necessary for systematic studies of metabolic pathways, to determine the specific requirements for growth and fully characterize metabolite production.
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| 12. |
- Nordberg Karlsson, Eva, et al.
(author)
-
Metabolic engineering of thermophilic bacteria for production of biotechnologically interesting compounds
- 2020
-
In: Biotechnological applications of extremophilic microorganisms. - : De Gruyter. - 9783110424331 ; , s. 73-96
-
Book chapter (peer-reviewed)abstract
- Many thermophilic bacteria are efficient biomass degraders (producing polysaccharide degrading enzymes and utilizing a great variety of substrates, e.g. lignocellulosic polymers, pentoses, hexoses, as well sugar acids, and sugar alcohols). This makes them interesting organisms as potential cell factories in a circular bioeconomy. Lignocellulosic and marine macroalgal biomasses are regarded as sustainable biorefinery feedstocks for the production of energy carriers and platform and specialty chemicals, thereby meeting impending fossil fuel shortage and counteracting accumulation of greenhouse gasses. However, progress in using thermophilic bacteria that utilize these feedstocks as carbon sources has been hampered by the lack of suitable engineering tools to improve the production profiles of interesting target metabolites as specific synthetic production pathways need to be inserted/modified or existing pathways optimized by metabolic engineering. In this chapter, we review the progress on the use of thermophilic bacteria in metabolic engineering and the available engineering tools and give examples of species for which successful engineering has been accomplished. Today, the majority of thermophilic bacteria targeted for production of compounds of industrial interest by metabolic engineering belong to the phylum Firmicutes (e.g. Thermoanaerobacterium, Caldocellulosiruptor, Geobacillus, and Bacillus), taking advantage of anaerobic catabolic pathways producing organic acids and alcohols. However, there are additional and aerobic species gaining interest concerning biomass degradation and the ability of carbon dioxide fixation as well as production of molecules of interest, and some examples of this are also given.
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| 13. |
- Nordberg Karlsson, Eva, et al.
(author)
-
The modular xylanase Xyn10A from Rhodothermus marinus is cell-attached, and its C-terminal domain has several putative homologues among cell-attached proteins within the phylum Bacteroidetes
- 2004
-
In: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968 .- 0378-1097. ; 241:2, s. 233-242
-
Journal article (peer-reviewed)abstract
- Until recently, the function of the fifth domain of the thermostable modular xylanase Xyn10A from Rhodothermus marinus was unresolved. A putative homologue to this domain was however identified in a mannanase (Man26A) from the same microorganism which raised questions regarding a common function. An extensive search of all accessible data-bases as well as the partially sequenced genomes of R. marinus and Cytophaga hutchinsonii showed that homologues of this domain were encoded by multiple genes in microorganisms in the phylum Bacteroidetes. Moreover, the domain occurred invariably at the C-termini of proteins that were predominantly extra-cellular/cell attached. A primary structure motif of three conserved regions including structurally important glycines and a proline was also identified suggesting a conserved 3D fold. This bioinformatic evidence suggested a possible role of this domain in mediating cell attachment. To confirm this theory, R. marinus was grown, and activity assays showed that the major part of the xylanase activity was connected to whole cells. Moreover, immunocytochemical detection using a Xyn10A-specific antibody proved presence of Xyn10A on the R. marinus cell surface. In the light of this, a revision of experimental data present on both Xyn10A and Man26A was performed, and the results all indicate a cell-anchoring role of the domain, suggesting that this domain represents a novel type of module that mediates cell attachment in proteins originating from members of the phylum Bacteroidetes.
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| 14. |
- Ron, Emanuel Y C, et al.
(author)
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Cultivation technology development of Rhodothermus marinus DSM 16675
- 2019
-
In: Extremophiles : life under extreme conditions. - : Springer Science and Business Media LLC. - 1433-4909. ; 23:6, s. 735-745
-
Journal article (peer-reviewed)abstract
- This work presents an evaluation of batch, fed-batch, and sequential batch cultivation techniques for production of R. marinus DSM 16675 and its exopolysaccharides (EPSs) and carotenoids in a bioreactor, using lysogeny broth (LB) and marine broth (MB), respectively, in both cases supplemented with 10 g/L maltose. Batch cultivation using LB supplemented with maltose (LBmalt) resulted in higher cell density (OD620 = 6.6) than use of MBmalt (OD620 = 1.7). Sequential batch cultivation increased the cell density threefold (OD620 = 20) in LBmalt and eightfold (OD620 = 14) in MBmalt. In both single and sequential batches, the production of carotenoids and EPSs using LBmalt was detected in the exponential phase and stationary phase, respectively, while in MBmalt formation of both products was detectable in both the exponential and stationary phases of the culture. Heteropolymeric EPSs were produced with an overall volumetric productivity (QE) of 0.67 (mg/L h) in MBmalt and the polymer contained xylose. In LB, QE was lower (0.1 mg/L h) and xylose could not be detected in the composition of the produced EPSs. In conclusion, this study showed the importance of a process design and medium source for production of R. marinus DSM 16675 and its metabolites.
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| 15. |
- Schiøtt, Morten, et al.
(author)
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Biorefining of brown seaweeds catalyzed through innovative enzyme processes
-
In: Industrial Biotechnology. - 1550-9087.
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Journal article (peer-reviewed)abstract
- The current expansion of seaweed farming to North America and Europe can be a cornerstone in a new “blue bioeconomy” in the Northern Hemisphere. In this domain, the focus of R&D efforts is on creating value-added products through new biorefining processes for valorizing the unique polysaccharides of seaweeds. Apart from direct consumption of seaweeds as food—particularly in the Asian cuisine—commercial seaweed products are primarily natural hydrocolloids used to make viscous suspensions and gels, but new valuable products exerting bioactivity are coming into focus. This recent development rests on targeted, gentle extraction and modification of the seaweed polysaccharides using tailormade bioprocessing enzyme technologies. Since brown seaweed cultivation is rising in the Northern Hemisphere, this article provides an overview of recent advances and prospects in brown seaweed biorefining.
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| 16. |
- Winestrand, Sandra, 1980-
(author)
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Industrial applications and properties of oxalate-degrading enzymes
- 2010
-
Doctoral thesis (other academic/artistic)abstract
- Oxalate-degrading enzymes were investigated with focus on potential applications in the pulp and paper industry and in active packaging. Changes introduced to make the pulp and paper industry more environmentally friendly, such as recirculation of process-water streams and elementary chlorine free bleaching of pulp, have led to increasing problems with precipitation of calcium oxalate. The potential of using enzymes for degradation of oxalic acid in industrial bleaching filtrates was explored to find a way to decrease the problem. The studies included chemical characterization and enzymatic treatments of 34 filtrates from kraft, mechanical, and sulfite pulping. Eight oxalate-degrading enzymes were included in the experiments. The treatments of the filtrates were affected by substances that inhibit oxalate-degrading enzymes. Multivariate data analysis, analytical treatment of filtrates with ion-exchange resins, and analysis of the effects of separate compounds on the enzyme activity were employed as tools to investigate inhibiting substances and groups of inhibitors. The experiments with ion-exchangers indicated that the inhibitors included anions, cations, as well as uncharged substances. Sulfite (≥1 mM) caused complete or almost complete inhibition of all oxalate-degrading enzymes so far examined, while the effects of chlorine oxyanions differed for the various enzymes investigated. A newly discovered oxalate decarboxylase was chosen for experiments performed directly in a mill producing mechanical pulp. The new enzyme degraded 70% of the oxalic acid in one hour, while the well-characterized oxalate decarboxylase from Aspergillus niger degraded <5% of the oxalic acid during the same period of time. Oxalate decarboxylase from the white-rot basidiomycete fungus Trametes versicolor was purified by using chromatographic methods and characterized with gel electrophoresis and tandem mass spectrometry. Results indicate that it is a 69-kDa heavily glycosylated enzyme with optimal activity at pH 2.5. Experiments designed to investigate the potential of using oxalate oxidase from barley in active packaging showed that it could be entrapped with retained catalytic activity in a latex-polymer matrix. Furthermore, the experiments indicate that oxalate oxidase can be used in active packaging either as an oxalic acid scavenger or as an oxygen scavenger.
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