| 1. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 2. |
- Thomas, HS, et al.
(författare)
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- 2019
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swepub:Mat__t
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| 3. |
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| 4. |
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| 5. |
- Sayed Ali Sayed, Mahmoud
(författare)
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Microbial and enzymatic syntheses of polymer building blocks through selective transformations of polyols and furans
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractTransition from fossil- to bio-based economy is a critical step towards reduction of greenhouse gas emissions and climate change, and hence for achievement of sustainable communities and environment. In order to be fossil-free, the chemical and material industry is in need of carbon-neutral building blocks from renewable resources for the diverse array of products that are currently produced from olefins and aromatics. Hence, new pathways for producing the same or novel chemical structures are needed. Industrial biotechnology offers a key technology area for transformation of biomass components or derivatives to chemical building blocks by the use of microorganisms or their enzymes. The thesis introduces new routes for microbial and enzymatic biotransformations of trimethylolpropane (TMP) and 5-hydroxymethyl furfural (HMF) to building blocks for polymers. TMP is an important industrial polyol with three hydroxyl groups produced from butyraldehyde and formaldehyde that can be potentially biobased, while HMF, a dehydration product of sugar, is totally biobased. The building block molecules produced from TMP include 2,2-bis(hydroxymethyl)butyric acid (BHMB), six membered cyclic carbonates, and from HMF are 5-hydroxymethyl-2-furan carboxylic acid (HMFCA), 5 formyl-2-furan carboxylic acid (FFCA) and 2,5-furan carboxylic acid (FDCA). Growing cells of Mycobacterium sp. MS1601 (previously Corynebacterium sp. ATCC 21245) was the only bacteria that showed the ability to selectively oxidize only one hydroxyl group of TMP to form BHMB at high yield. After optimization of the process parameters and employing high cell density cultivations in a sequential batch mode with cell recycling and cell bleeding, the volumetric productivity of BHMB was improved from 0.02 g/L.h to 0.2 g/L.h to yield 21 g/L BHMB, the highest amount reported so far. Moreover, BHMB was recovered from the reaction medium by anion exchange resin at 78% yield. Transesterification of TMP with methacrylic acid and its derivatives including methyl, ethyl vinyl and dimethyl carbonate (DMC) was investigated using immobilized lipase (Novozym435) in solvent free medium in order to produce methacrylate functionalized six-membered cyclic carbonates. The results obtained from the experimental part and in-silico analysis indicate that methyl and ethyl methacrylate were preferable substrates for the enzyme to give the product with 61.3 % yield and 73% selectivity after 9 hours reaction. Also, the functionalized cyclic carbonate was purified from the reaction solution using silica chromatography at 60.5% yield. Even the production of bio-based TMP under mild conditions was demonstrated by condensation of bio-based butyraldehyde with formaldehyde produced by oxidation of the corresponding alcohols using Gluconobacter oxydans cells and alcohol oxidase, respectively. Oxidation of crude 5-HMF to HMFCA at 100 % selectivity and yield was achieved using resting cells of G. oxydans DSM 50049. The bacteria show the ability to oxidize 31.5 g/L of crude HMF completely to HMFCA after only 6 h of the reaction, indicating that the bacteria is tolerant to the antimicrobial activity and high concentration of HMFCA. The product was recovered from the reaction with 98% purity using a simple liquid-liquid extraction step. On the other hand, Mycobacterium sp. MS1601 cells activated by growth in glycerol, oxidized HMF to FDCA and HMFCA with 60% and 40% yield, respectively. A gene sequence encoding HMF oxidase (HMFO) like enzyme was identified in the genome sequence of Mycobacterium sp. MS1601, cloned and expressed in E.coli BL21 (DE3), and the enzyme was purified and characterized. The enzyme oxidized HMF to diformyl furan (DFF) followed by conversion to FFCA at 100 % yield without further conversion to FDCA. In-silico analysis of the HMFO-Myc1 indicated that catalytic histidine is positioned at 445 and tyrosine 444 and 443 residues, which are directing the substrate into the right position in the active site, hinders FFCA from being accommodated in the right position, which motivates further studies on engineering the enzyme to enable conversion of FFCA to FDCA.
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| 6. |
- Sayed, Mahmoud, et al.
(författare)
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Complete genome sequence of Mycobacterium sp. MS1601, a bacterium performing selective oxidation of polyols
- 2017
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Ingår i: Genome Announcements. - 2169-8287. ; 5:15
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Tidskriftsartikel (refereegranskat)abstract
- Corynebacterium sp. (ATCC 21245) is reclassified here as Mycobacterium sp. MS1601 based on 16S rRNA gene and complete-genome sequence analysis. It is able to oxidize branched polyols to corresponding hydroxycarboxylic acids. The total size of the genome sequence was 6,829,132 bp, including one circular chromosome of 6,407,860 bp.
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| 7. |
- Sayed, Mahmoud, et al.
(författare)
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Enhanced selective oxidation of trimethylolpropane to 2,2-bis(hydroxymethyl)butyric acid using Corynebacterium sp. ATCC 21245
- 2017
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113. ; 63, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- 2,2-Bis(hydroxymethyl)butyric acid (BHMB) is an important multifunctional chemical for the emerging bio-based polymer industry. It can be produced from trimethylolpropane (TMP) by selective oxidation using growing cells of Corynebacterium sp. ATCC 21245. However, this process is limited by the low volumetric productivity and low concentration of the final product. In the present study, we performed sequential batch operation with cell recycling in media containing glycerol, acetic acid, and increasing concentrations of yeast extract. This approach enhanced the conversion of 10 and 15g/L TMP to 11.0 and 16.3g/L BHMB at rates of 0.50 and 0.20g/L.h, respectively. Applying a cell bleeding strategy resulted in an overall 10-fold improvement in productivity. The consequently prolonged biocatalyst viability resulted in a quantitative conversion of 20g/L TMP to 22.3g/L BHMB and a yield of 1.10gBHMB/gTMP (100% molar yield). This work facilitates further studies of the selective oxidation on other industrially important polyols.
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| 8. |
- Sayed, Mahmoud, et al.
(författare)
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Selective oxidation of trimethylolpropane to 2,2-bis(hydroxymethyl)butyric acid using growing cells of Corynebacterium sp. ATCC 21245.
- 2016
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 1873-4863 .- 0168-1656. ; 221, s. 62-69
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Tidskriftsartikel (refereegranskat)abstract
- Multifunctional chemicals including hydroxycarboxylic acids are gaining increasing interest due to their growing applications in the polymer industry. One approach for their production is a biological selective oxidation of polyols, which is difficult to achieve by conventional chemical catalysis. In the present study, trimethylolpropane (TMP), a trihydric alcohol, was subjected to selective oxidation using growing cells of Corynebacterium sp. ATCC 21245as a biocatalyst and yielding the dihydroxy-monocarboxylic acid, 2,2-bis(hydroxymethyl)butyric acid (BHMB). The study revealed that co-substrates are crucial for this reaction. Among the different evaluated co-substrates, a mixture of glucose, xylose and acetate at a ratio of 5:5:2 was found optimum. The optimal conditions for biotransformation were pH 8, 1v/v/m airflow and 500rpm stirring speed. In batch mode of operation, 70.6% of 5g/l TMP was converted to BHMB in 10 days. For recovery of the product the adsorption pattern of BHMB to the anion exchange resin, Ambersep(®)900 (OH(-)), was investigated in batch and column experiments giving maximum static and dynamic binding capacities of 135 and 144mg/g resin, respectively. BHMB was separated with 89.7% of recovery yield from the fermentation broth. The approach is applicable for selective oxidation of other highly branched polyols by biotransformation.
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| 9. |
- Warlin, Niklas, et al.
(författare)
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A rigid spirocyclic diol from fructose-based 5-hydroxymethylfurfural: synthesis, life-cycle assessment, and polymerization for renewable polyesters and poly(urethane-urea)s
- 2019
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Ingår i: Green Chemistry. - 1463-9270. ; 21:24, s. 6667-6684
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Tidskriftsartikel (refereegranskat)abstract
- There is currently an intensive development of sugar-based building blocks toward the production of renewable high performance plastics. In this context, we report on the synthesis of a rigid diol with a spirocyclic structure via a one-step acid-catalyzed acetalation of fructose-sourced 5-hydroxymethylfurfural and pentaerythritol. Preliminary life cycle assessment (LCA) indicated that the spiro-diol produced 46% less CO2 emission than bio-based 1,3-propanediol. Polymerizations of the spiro-diol together with another sugar-based flexible 1,6-hexanediol for the production of polyesters and poly(urethane-urea)s were investigated, and reasonably high molecular weights were achieved when up to 20 or 60 mol% spiro-diol was used for polyesters or poly(urethane-urea)s, respectively. The glass transition temperatures (Tg) of the polyesters and poly(urethane-urea)s significantly increased upon the incorporation of the rigid spirocyclic structure. On the other hand, it was observed that the spiro-diol was heat-sensitive, which could cause coloration andpartial crosslinking when >10%(with respect to dicarboxylate) was used for the polyester synthesis at high temperatures.The results indicated that the polymerization conditions have to be carefully controlled in order to avoid coloration and side reactions during the polyester formation when >10% of the spiro-diol is used. However, when the spiro-diol was used for the synthesis of polyurethanes at lower temperature, the side reactions were insignificant. This suggests that the new spiro-diol can be potentially suitable toward the production of sustainable rigid polyurethane materials like coatings or foams, as well as renewable polyesters after further optimization of the polymerization conditions.
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| 10. |
- Bornadel, Amin, et al.
(författare)
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Six-membered cyclic carbonates from trimethylolpropane : Lipase-mediated synthesis in a flow reactor and in silico evaluation of the reaction
- 2017
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Ingår i: Biotechnology Progress. - : Wiley. - 8756-7938. ; 33:2, s. 375-382
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Tidskriftsartikel (refereegranskat)abstract
- Six-membered cyclic carbonates with hydroxyl and methoxycarbonyloxy functional groups were prepared by transesterification of trimethylolpropane (TMP) with dimethylcarbonate (DMC) by solvent-free lipase-mediated flow reaction followed by thermal cyclization. The flow reaction efficiency was evaluated using different configurations of reactor consisting of packed beds of Novozym®435 (immobilized Candida antarctica lipase B—CalB—a.k.a. N435) and molecular sieves, flowrate, and biocatalyst loads. The mixed column of the biocatalyst and molecular sieves, allowing rapid and efficient removal of the by-product—methanol—was the most efficient setup. Higher conversion (81.6%) in the flow reaction compared to batch process (72%) was obtained using same amount of N435 (20% (w/w) N435:TMP) at 12 h, and the undesirable dimer and oligomer formation were suppressed. Moreover, the product was recovered easily without extra separation steps, and the biocatalyst and the molecular sieves remained intact for subsequent regeneration and recycling. The reaction of CalB with DMC and the primary transesterification product, monocarbonated TMP, respectively, as acyl donors was evaluated by in silico modeling and empirically to determine the role of the enzyme in the formation of cyclic carbonates and other side products. DMC was shown to be the preferred acyl donor, suggesting that TMP and its carbonated derivatives serve only as acyl acceptors in the lipase-catalyzed reaction. Subsequent cyclization to cyclic carbonate is catalyzed at increased temperature and not by the enzyme.
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