| 1. |
- Ylitervo, Päivi
(author)
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Concepts for improving ethanol productivity from lignocellulosic materials : encapsulated yeast and membrane bioreactors
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Lignocellulosic biomass is a potential feedstock for production of sugars, which can be fermented into ethanol. The work presented in this thesis proposes some solutions to overcome problems with suboptimal process performance due to elevated cultivation temperatures and inhibitors present during ethanol production from lignocellulosic materials. In particular, continuous processes operated at high dilution rates with high sugar utilisation are attractive for ethanol fermentation, as this can result in higher ethanol productivity. Both encapsulation and membrane bioreactors were studied and developed to achieve rapid fermentation at high yeast cell density. My studies showed that encapsulated yeast is more thermotolerant than suspended yeast. The encapsulated yeast could successfully ferment all glucose during five consecutive batches, 12 h each at 42 °C. In contrast, freely suspended yeast was inactivated already in the second or third batch. One problem with encapsulation is, however, the mechanical robustness of the capsule membrane. If the capsules are exposed to e.g. high shear forces, the capsule membrane may break. Therefore, a method was developed to produce more robust capsules by treating alginate-chitosan-alginate (ACA) capsules with 3-aminopropyltriethoxysilane (APTES) to get polysiloxane-ACA capsules. Of the ACA-capsules treated with 1.5% APTES, only 0–2% of the capsules broke, while 25% of the untreated capsules ruptured within 6 h in a shear test. In this thesis membrane bioreactors (MBR), using either a cross-flow or a submerged membrane, could successfully be applied to retain the yeast inside the reactor. The cross-flow membrane was operated at a dilution rate of 0.5 h-1 whereas the submerged membrane was tested at several dilution rates, from 0.2 up to 0.8 h-1. Cultivations at high cell densities demonstrated an efficient in situ detoxification of very high furfural levels of up to 17 g L-1 in the feed medium when using a MBR. The maximum yeast density achieved in the MBR was more than 200 g L-1. Additionally, ethanol fermentation of nondetoxified spruce hydrolysate was possible at a high feeding rate of 0.8 h-1 by applying a submerged membrane bioreactor, resulting in ethanol productivities of up to 8 g L-1 h-1. In conclusion, this study suggests methods for rapid continuous ethanol production even at stressful elevated cultivation temperatures or inhibitory conditions by using encapsulation or membrane bioreactors and high cell density cultivations.
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| 2. |
- Akinbomi, Julius, et al.
(author)
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Development and dissemination strategies for accelerating biogas production in Nigeria
- 2014
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In: BioResources. - : NC State University. - 1930-2126. ; 9:3, s. 5707-5737
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Journal article (peer-reviewed)abstract
- Following the worsening energy crisis of unreliable electricity and unaffordable petroleum products coupled with the increase number of poverty-stricken people in Nigeria, the populace is desperately in need of cheap alternative energy supplies that will replace or complement the existing energy sources. Previous efforts by the government in tackling the challenge by citizenship sensitization of the need for introduction of biofuel into the country’s energy mix have not yielded the expected results because of a lack of sustained government effort. In light of the shortcomings, this study assesses the current potential of available biomass feedstock for biogas production in Nigeria, and further proposes appropriate biogas plants, depending on feedstock type and quantity, for the six geopolitical zones in Nigeria. Besides, the study proposes government-driven biogas development systems that could be effectively used to harness, using biogas technology, the estimated 270 TWh of potential electrical energy from 181 million tonnes of available biomass, in the advancement of electricity generation and consequent improvement of welfare in Nigeria.
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| 3. |
- Akintunde, Moyinoluwa, et al.
(author)
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Bacterial Cellulose Production from agricultural Residues by two Komagataeibacter sp. Strains
- 2022
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In: Bioengineered. - : Informa UK Limited. - 2165-5979 .- 2165-5987. ; 13:4, s. 10010-10025
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Journal article (peer-reviewed)abstract
- Agricultural residues are constantly increasing with increased farming processes, and improper disposal is detrimental to the environment. Majority of these waste residues are rich in lignocellulose, which makes them suitable substrate for bacterial fermentation in the production of valueadded products. In this study, bacterial cellulose (BC), a purer and better form of cellulose, was produced by two Komagataeibacter sp. isolated from rotten banana and kombucha drink using corncob (CC) and sugarcane bagasse (SCB) enzymatic hydrolyzate, under different fermentation conditions, that is, static, continuous, and intermittent agitation. The physicochemical and mechanical properties of the BC films were then investigated by Fourier Transformed Infrared Spectroscopy (FTIR), Thermogravimetry analysis, Field Emission Scanning Electron Microscopy (FESEM), and Dynamic mechanical analysis. Agitation gave a higher BC yield, with Komagataeibacter sp. CCUG73629 producing BC from CC with a dry weight of 1.6 g/L and 1.4 g/L under continuous and intermittent agitation, respectively, compared with that of 0.9 g/L in HS medium. While BC yield of dry weight up to 1.2 g/L was obtained from SCB by Komagataeibacter sp. CCUG73630 under continuous agitation compared to that of 0.3 g/L in HS medium. FTIR analysis showed BC bands associated with cellulose I, with high thermal stability. The FE-SEM analysis showed that BC fibers were highly ordered and densely packed. Although the BC produced by both strains showed similar physicochemical and morphological properties, the BC produced by the Komagataeibacter sp. CCUG73630 in CC under intermittent agitation had the best modulus of elasticity, 10.8 GPa and tensile strength, 70.9 MPa. [GRAPHICS]
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| 4. |
- Andersson, Lars, 1977, et al.
(author)
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Distribution of candidate genes for experimentally induced arthritis in rats
- 2010
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In: BMC GENOMICS. - : BioMed Central Ltd.. - 1471-2164. ; 11
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Journal article (peer-reviewed)abstract
- Background Rat models are frequently used to link genomic regions to experimentally induced arthritis in quantitative trait locus (QTL) analyses. To facilitate the search for candidate genes within such regions, we have previously developed an application (CGC) that uses weighted keywords to rank genes based on their descriptive text. In this study, CGC is used for analyzing the localization of candidate genes from two viewpoints: distribution over the rat genome and functional connections between arthritis QTLs. Methods To investigate if candidate genes identified by CGC are more likely to be found inside QTLs, we ranked 2403 genes genome wide in rat. The number of genes within different ranges of CGC scores localized inside and outside QTLs was then calculated. Furthermore, we investigated if candidate genes within certain QTLs share similar functions, and if these functions could be connected to genes within other QTLs. Based on references between genes in OMIM, we created connections between genes in QTLs identified in two distinct rat crosses. In this way, QTL pairs with one QTL from each cross that share an unexpectedly high number of gene connections were identified. The genes that were found to connect a pair of QTLs were then functionally analysed using a publicly available classification tool. Results Out of the 2403 genes ranked by the CGC application, 1160 were localized within QTL regions. No difference was observed between highly and lowly rated genes. Hence, highly rated candidate genes for arthritis seem to be distributed randomly inside and outside QTLs. Furthermore, we found five pairs of QTLs that shared a significantly high number of interconnected genes. When functionally analyzed, most genes connecting two QTLs could be included in a single functional cluster. Thus, the functional connections between these genes could very well be involved in the development of an arthritis phenotype. Conclusions From the genome wide CGC search, we conclude that candidate genes for arthritis in rat are randomly distributed between QTL and non-QTL regions. We do however find certain pairs of QTLs that share a large number of functionally connected candidate genes, suggesting that these QTLs contain a number of genes involved in similar functions contributing to the arthritis phenotype.
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| 5. |
- Andersson, Lars, 1977, et al.
(author)
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Finding Genes Contributing to the Arthritis Phenotype by Comparing Rat and Human Genome Data
- 2004
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In: Health Informatics Journal. - : SAGE Publications. - 1460-4582 .- 1741-2811. ; 10:1, s. 71-75
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Journal article (peer-reviewed)abstract
- Published quantitative trait locus (QTL) data, as well as all known rat genes and DNA markers, have since 1993 been collected and made easily accessible at the rat genome database, RatMap. The objective of the present study is to fully integrate available data concerning rat models with human genome information. The final goal of this process is to make results from any rat model experiment directly applicable to humans. The overall goal of this work is to create an automatic system which, for any given rat chromosomal region associated with a QTL, will characterize both mapped rat genes and all putative homologous human genes in that region. This article reports the use of the web application to find human gene candidates contributing to an arthritis phenotype.
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| 6. |
- Bazooyar, Faranak, 1972, et al.
(author)
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Computational studies of water and carbon dioxide interactions with cellobiose
- 2015
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In: Journal of Molecular Modeling. - : Springer Science and Business Media LLC. - 0948-5023 .- 1610-2940. ; 21:1, s. 1-9
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Journal article (peer-reviewed)abstract
- B3LYP/6-311++G** with dispersion correction (DFT-D) was used to study local and global minimum energy structures of water (H2O) or carbon dioxide (CO2) bonding with a pair of cellobiose molecules. The calculations showed that neither the H2O nor the CO2 prefer to be between the cellobiose molecules, and that the minimum energy structures occur when these molecules bond to the outer surface of the cellobiose pair. The calculations also showed that the low energy structures have a larger number of inter-cellobiose hydrogen bonds than the high energy structures. These results indicate that penetration of H2O or CO2 between adjacent cellobiose pairs, which would assist steam or supercritical CO2 (SC-CO2) explosion of cellulose, is not energetically favored. Comparison of the energies obtained with DFT-D and DFT (the same method but without dispersion correction) show that both hydrogen bonds and van der Waals interactions play an important role in cellobiose-cellobiose interactions.
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| 7. |
- Bulkan, Gülru, et al.
(author)
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Retrofitting analysis of a biorefinery : Integration of 1st and 2nd generation ethanol through organosolv pretreatment of oat husks and fungal cultivation
- 2021
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In: Bioresource Technology Reports. - : Elsevier Ltd. - 2589-014X. ; 15
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Journal article (peer-reviewed)abstract
- This study was dedicated to techno-economic analysis of an integrated 1st and 2nd generation biorefinery, where the organosolv pretreated oat husk and thin stillage is valorized through filamentous fungi and baker yeast. By this strategy, process economy can benefit from multiple value-added products including lignin (80% purity), and protein-rich biomass as feed/food ingredients. Ethanol recovery of organosolv pretreatment benefits the already existing equipment in 1st generation ethanol plant. The best results shows that the integration of 10 tons/h oat husk into a process using 18.8 tons/h grains results in increasing ethanol production from 5.2 to 7.5 tons/h, in addition to 1.6 tons/h lignin (80% purity) and 7.6 tons/h fungal biomass. Integrated process is beneficial not only for 2nd but also for 1st generation ethanol production. Selling the fungal biomass as feed and food increased the net present value (NPV) in comparison to conventional ethanol plant by 71% and 7.9-fold, respectively. © 2021 The Authors
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| 8. |
- Cho, Sung-Woo, et al.
(author)
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Injection-molded nanocomposites and materials based on wheat gluten
- 2011
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In: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 48:1, s. 146-152
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Journal article (peer-reviewed)abstract
- This is, to our knowledge, the first study of the injection molding of materials where wheat gluten (WG) is the main component. In addition to a plasticizer (glycerol), 5 wt.% natural montmorillonite clay was added. X-ray indicated intercalated clay and transmission electron microscopy indicated locally good clay platelet dispersion. Prior to feeding into the injection molder, the material was first compression molded into plates and pelletized. The filling of the circular mold via the central gate was characterized by a divergent flow yielding, in general, a stronger and stiffer material in the circumferential direction. It was observed that 20–30 wt.% glycerol yielded the best combination of processability and mechanical properties. The clay yielded improved processability, plate homogeneity and tensile stiffness. IR spectroscopy and protein solubility indicated that the injection molding process yielded a highly aggregated structure. The overall conclusion was that injection molding is a very promising method for producing WG objects.
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| 9. |
- Dehdarirad, Tahereh, 1984, et al.
(author)
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Use of positive terms and certainty language in retracted and non-retracted articles: The case of biochemistry
- 2023
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In: Journal of Information Science. - 0165-5515 .- 1741-6485. ; In Press
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Journal article (peer-reviewed)abstract
- This study aimed to compare retracted (due to misconduct) and non-retracted articles in biochemistry, in terms of proportion of positive terms, certainty score and different certainty aspects. The data set of this study composed of 662 retracted and non-retracted articles published in the time period of 2018-2020 and indexed in Scopus. These 662 articles accounted for 331 non-retracted and 331 retracted articles, which were matched using matching and covariate balancing analysis. The analysis in this article was done using several regression models. Regarding the use of positive terms, the findings showed that retracted articles were 16% less probable to use positive terms in abstracts, titles and findings presented in conclusion and discussion compared with non-retracted articles. In addition, the results regarding the analysis of certainty language, showed that retracted articles were 15% less probable to use certain language, measured by certainty score, in presenting their scientific findings. Finally, regarding the certainty aspects, the results of regression models showed that retracted articles had 11% less likelihood to present their research findings using certain probability aspect.
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| 10. |
- Forgacs, G., et al.
(author)
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Pretreatment of chicken feather waste for improved biogas production
- 2013
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In: Applied Biochemistry and Biotechnology. - : Humana Press, Inc.. - 0273-2289 .- 1559-0291. ; 169:7, s. 2016-2028
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Journal article (peer-reviewed)abstract
- This study deals with the utilization of chicken feather waste as a substrate for anaerobic digestion and improving biogas production by degradation of the compact structure of the feather keratin. In order to increase the digestibility of the feather, different pretreatments were investigated, including thermal pretreatment at 120 °C for 10 min, enzymatic hydrolysis with an alkaline endopeptidase [0.53–2.66 mL/g volatile solids (VS) feathers] for 0, 2, or 24 h at 55 °C, as well as a combination of these pretreatments. The effects of the treatments were then evaluated by anaerobic batch digestion assays at 55 °C. The enzymatic pretreatment increased the methane yield to 0.40 Nm3/kg VSadded, which is 122 % improvement compared to the yield of the untreated feathers. The other treatment conditions were less effective, increasing the methane yield by 11–50 %. The long-term effects of anaerobic digestion of feathers were examined by co-digestion of the feather with organic fraction of municipal solid waste performed with and without the addition of enzyme. When enzyme was added together with the feed, CH4 yield of 0.485 Nm3/kg VS−1 d−1 was achieved together with a stable reactor performance, while in the control reactor, a decrease in methane production, together with accumulation of undegraded feather, was observed.
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