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Sökning: WFRF:(Karlsson R.) > Teknik

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1.
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2.
  • Sajib, Mursalin, 1987, et al. (författare)
  • Valorization of Brewer's spent grain to prebiotic oligosaccharide: Production, xylanase catalyzed hydrolysis, in-vitro evaluation with probiotic strains and in a batch human fecal fermentation model
  • 2018
  • Ingår i: Journal of Biotechnology. - : Elsevier BV. - 1873-4863 .- 0168-1656. ; 268, s. 61-70
  • Tidskriftsartikel (refereegranskat)abstract
    • Brewer's spent grain (BSG) accounts for around 85% of the solid by-products from beer production. BSG was first extracted to obtain water-soluble arabinoxylan (AX). Using subsequent alkali extraction (0.5 M KOH) it was possible to dissolve additional AX. In total, about 57% of the AX in BSG was extracted with the purity of 45–55%. After comparison of nine xylanases, Pentopan mono BG, a GH11 enzyme, was selected for hydrolysis of the extracts to oligosaccharides with minimal formation of monosaccharides. Growth of Bifidobacterium adolescentis (ATCC 15703) was promoted by the enzymatic hydrolysis to arabinoxylooligosaccharides, while Lactobacillus brevis (DSMZ 1264) utilized only unsubstituted xylooligosaccharides. Furthermore, utilization of the hydrolysates by human gut microbiota was also assessed in a batch human fecal fermentation model. Results revealed that the rates of fermentation of the BSG hydrolysates by human gut microbiota were similar to that of commercial prebiotic fructooligosaccharides, while inulin was fermented at a slower rate. In summary, a sustainable process to valorize BSG to functional food ingredients has been proposed.
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3.
  • Allahgholi, Leila, et al. (författare)
  • Composition analysis and minimal treatments to solubilize polysaccharides from the brown seaweed Laminaria digitata for microbial growth of thermophiles
  • 2020
  • Ingår i: Journal of Applied Phycology. - : Springer Science and Business Media LLC. - 0921-8971 .- 1573-5176. ; 32:3, s. 1933-1947
  • Tidskriftsartikel (refereegranskat)abstract
    • Brown macroalgae (Phaeophyta) hold high potential as feedstock for biorefineries due to high biomass productivity and carbohydrate content. They are, however, a challenging, unconventional feedstock for microbial refining and several processing problems need to be solved to make them a viable option. Pre-treatment is necessary to enhance accessibility and solubility of the biomass components but should be minimal and mild to assure sustainable and cost-effective processing. Here, two routes to pre-treatLaminaria digitata to release polysaccharides were investigated: hot water pre-treatment by autoclaving (121 °C, 20 min or 60 min) and a two-step extraction with mild acid (0.1 M HCl) followed by alkaline treatment. Hot water pre-treatment resulted in partial extraction of a mixture of polysaccharides consisting of alginate, fucoidan and laminarin. After mild acid pre-treatment, alginate was found in the remaining insoluble residues and was extracted in a second step via alkaline treatment using Na2CO3 (0.15 M) at 80 °C and CaCl2 (10%) for the precipitation. In addition to carbohydrates, a fraction of other components such as proteins, phenolic compounds, minerals and trace elements was detected in the extracts. Cultivation of the thermophilic bacterial strains Rhodothermus marinus DSM 16675 and Bacillus methanolicus MGA3 (ATCC 53907) in media supplemented with the respective extracts resulted in growth of both strains, indicating that they were able to utilize the available carbon source for growth. R. marinus displayed the highest cell density in the medium containing the extract from acid pre-treatment, whereas B. methanolicus growth was highest with the extract from hot water pre-treatment.
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4.
  • Ramjaun, T., et al. (författare)
  • Effect of interpass temperature on residual stresses in multipass welds produced using low transformation temperature filler alloy
  • 2014
  • Ingår i: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 19:1, s. 44-51
  • Tidskriftsartikel (refereegranskat)abstract
    • Weld filler alloys that exploit transformation plasticity through low austenite to martensite transformation temperatures offer an effective method of reducing residual stresses in strong steel welds. However, in multipass welds, the heat input from later weld passes may be insufficient to retransform prior welding passes, leading to the accumulation of thermally induced strains and elevated residual stresses. In this work, the residual stress distributions produced around arc welds fabricated with a martensitic weld filler alloy that transforms at a low temperature have been studied as a function of the number of passes deposited and the interpass temperature. It is found that when the interpass temperature is above the transformation temperature of the weld metal, the entire multipass weld transforms as a single entity, thus permitting the optimum exploitation of the transformation plasticity. In contrast, the deposition of new metal with a relatively low interpass temperature leads to increased residual stresses in the underlying layers, reducing or eliminating the beneficial stress states previously created.
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5.
  • Huang, Fang, et al. (författare)
  • Cultivation of the gut bacterium Prevotella copri DSM 18205T using glucose and xylose as carbon sources
  • 2021
  • Ingår i: MicrobiologyOpen. - : Wiley. - 2045-8827. ; 10:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Prevotella copri DSM18205T is a human gut bacterium, suggested as a next-generation probiotic. To utilize it as such, it is, however, necessary to grow the species in a reproducible manner. Prevotella copri has previously been reported to be highly sensitive to oxygen, and hence difficult to isolate and cultivate. This study presents successful batch cultivation strategies for viable strain inoculations and growth in both serum bottles and a stirred tank bioreactor (STR), without the use of an anaerobic chamber, as long as the cells were kept in the exponential growth phase. A low headspace volume in the STR was important to reach high cell density. P. copri utilized xylose cultivated in Peptone Yeast Xylose medium (PYX medium), resulting in a comparable growth rate and metabolite production as in Peptone Yeast Glucose medium (PYG medium) in batch cultivations at pH 7.2.Up to 5 g/L of the carbon source was consumed, leading to the production of succinic acid, acetic acid, and formic acid, and cell densities (OD620 nm ) in the range 6-7.5. The highest yield of produced succinic acid was 0.63 ± 0.05 g/g glucose in PYG medium cultivations and 0.88 ± 0.06 g/g xylose in PYX medium cultivations.
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6.
  • Karlsson, C., et al. (författare)
  • Preface
  • 2014
  • Ingår i: Knowledge, Innovation and Space. - : Edward Elgar Publishing. - 9781848449015 ; , s. IX-X
  • Bokkapitel (refereegranskat)
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7.
  • Khaleghipour, Leila, et al. (författare)
  • Extraction of sugarcane bagasse arabinoxylan, integrated with enzymatic production of xylo-oligosaccharides and separation of cellulose
  • 2021
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 14:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Sugarcane processing roughly generates 54 million tonnes sugarcane bagasse (SCB)/year, making SCB an important material for upgrading to value-added molecules. In this study, an integrated scheme was developed for separating xylan, lignin and cellulose, followed by production of xylo-oligosaccharides (XOS) from SCB. Xylan extraction conditions were screened in: (1) single extractions in NaOH (0.25, 0.5, or 1 M), 121 °C (1 bar), 30 and 60 min; (2) 3 × repeated extraction cycles in NaOH (1 or 2 M), 121 °C (1 bar), 30 and 60 min or (3) pressurized liquid extractions (PLE), 100 bar, at low alkalinity (0-0.1 M NaOH) in the time and temperature range 10-30 min and 50-150 °C. Higher concentration of alkali (2 M NaOH) increased the xylan yield and resulted in higher apparent molecular weight of the xylan polymer (212 kDa using 1 and 2 M NaOH, vs 47 kDa using 0.5 M NaOH), but decreased the substituent sugar content. Repeated extraction at 2 M NaOH, 121 °C, 60 min solubilized both xylan (85.6% of the SCB xylan), and lignin (84.1% of the lignin), and left cellulose of high purity (95.8%) in the residuals. Solubilized xylan was separated from lignin by precipitation, and a polymer with β-1,4-linked xylose backbone substituted by arabinose and glucuronic acids was confirmed by FT-IR and monosaccharide analysis. XOS yield in subsequent hydrolysis by endo-xylanases (from glycoside hydrolase family 10 or 11) was dependent on extraction conditions, and was highest using xylan extracted by 0.5 M NaOH, (42.3%, using Xyn10A from Bacillus halodurans), with xylobiose and xylotriose as main products. The present study shows successful separation of SCB xylan, lignin, and cellulose. High concentration of alkali, resulted in xylan with lower degree of substitution (especially reduced arabinosylation), while high pressure (using PLE), released more lignin than xylan. Enzymatic hydrolysis was more efficient using xylan extracted at lower alkaline strength and less efficient using xylan obtained by PLE and 2 M NaOH, which may be a consequence of polymer aggregation, via remaining lignin interactions.
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8.
  • Knowledge, innovation and space
  • 2014
  • Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
    • The contributions in this volume extend our understanding about the different ways distance impacts the knowledge conversion process. Knowledge itself is a raw input into the innovation process which can then transform it into an economically useful output such as prototypes, patents, licences and new companies. New knowledge is often tacit and thus tends to be highly localized, as indeed is the conversion process. Consequently, as the book demonstrates, space or distance matter significantly in the transformation of raw knowledge into beneficial knowledge.
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9.
  • Nordberg Karlsson, Eva, et al. (författare)
  • Metabolic engineering of thermophilic bacteria for production of biotechnologically interesting compounds
  • 2020
  • Ingår i: Biotechnological applications of extremophilic microorganisms. - : De Gruyter. - 9783110424331 ; , s. 73-96
  • Bokkapitel (refereegranskat)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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10.
  • Romano-Rodriguez, A., et al. (författare)
  • Epitaxial growth of beta-SiC on ion-beam synthesized beta-SiC : Structural characterization
  • 2000
  • Ingår i: Silicon Carbide and Related Materials - 1999 Pts, 1 & 2. - : Trans Tech Publications Inc.. ; , s. 309-312
  • Konferensbidrag (refereegranskat)abstract
    • In this work we present for the first time, to our knowledge, the CVD epitaxial growth of β-SiC using an ion beam synthesized (IBS) β-SiC layer as seed, which has been formed by multiple implantation into Si wafers at 500 °C. The ion beam synthesized continuous layer is constituted by β-SiC nanocrystals that are well oriented relative to the silicon substrate. Comparison of the epitaxial growth on these samples with that on silicon test samples, both on and off-axis, is performed. The results show that the epitaxial growth can be achieved on the IBS samples without the need of the carbonization step and that the structural quality of the CVD layer is comparable to that obtained on a carbonized silicon sample. Improvement of the quality of the deposited layer is proposed.
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