| 1. |
- Bazooyar, Faranak, 1972, et al.
(författare)
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Molecular Modelling of Cellulose Dissolution
- 2013
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Ingår i: Journal of Computational and Theoretical Nanoscience. - : American Scientific Publishers. - 1546-1955 .- 1546-1963. ; 10:11, s. 2639-2646
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present computational studies that shed light on the molecular mechanism of the initial stages of cellulose dissolution in saturated steam, which is an important pretreatment step in the conversion of lignocellulose to biofuel. The COMPASS, Dreiding and Universal molecular mechanics force fields and the B3LYP density functional with 6-311G, 6-311++G(d, p) and 6-311++G(2d, 2p) basis sets were used to study systems containing glucose, cellobiose and water. These molecular systems were studied since they are sufficiently small to perform the density functional theory calculations in a tractable time, while also being relevant to the dissolution of cellulose in saturated steam. Comparison of the energies and structures obtained from the three force fields with those obtained from the first principles method showed that the COMPASS force field is preferred to the other two and that this force field gives similar structures obtained from the first principles method. This supports the validity of the COMPASS force field for studying cellulose dissolution in saturated steam, and preliminary simulations were performed using grand canonical Monte Carlo and molecular dynamics simulations of cellulose dissolution in saturated steam at 100 degrees C and 1 bar, 160 degrees C and 6.2 bar, and 250 degrees C and 39.7 bar. The results show that the cellulose crystal dissolves in saturated steam at the higher temperatures and pressures.
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| 2. |
- Forgacs, G., et al.
(författare)
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Pretreatment of chicken feather waste for improved biogas production
- 2013
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Ingår i: Applied Biochemistry and Biotechnology. - : Humana Press, Inc.. - 0273-2289 .- 1559-0291. ; 169:7, s. 2016-2028
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Isroi, Isroi, 1974, et al.
(författare)
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Structural Changes of Oil Palm Empty Fruit Bunch (OPEFB) after Fungal and Phosphoric Acid Pretreatment
- 2012
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Ingår i: Molecules. - : MDPI AG. - 1420-3049 .- 1420-3049 .- 1431-5157. ; 17:12, s. 14995-15012
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Tidskriftsartikel (refereegranskat)abstract
- Oil palm empty fruit bunch (OPEFB) was pretreated using white-rot fungus Pleurotus floridanus, phosphoric acid or their combination, and the results were evaluated based on the biomass components, and its structural and morphological changes. The carbohydrate losses after fungal, phosphoric acid, and fungal followed by phosphoric acid pretreatments were 7.89%, 35.65%, and 33.77%, respectively. The pretreatments changed the hydrogen bonds of cellulose and linkages between lignin and carbohydrate, which is associated with crystallinity of cellulose of OPEFB. Lateral Order Index (LOI) of OPEFB with no pretreatment, with fungal, phosphoric acid, and fungal followed by phosphoric acid pretreatments were 2.77, 1.42, 0.67, and 0.60, respectively. Phosphoric acid pretreatment showed morphological changes of OPEFB, indicated by the damage of fibre structure into smaller particle size. The fungal-, phosphoric acid-, and fungal followed by phosphoric acid pretreatments have improved the digestibility of OPEFB's cellulose by 4, 6.3, and 7.4 folds, respectively.
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| 4. |
- Kabir, M. M., et al.
(författare)
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Biogas production from lignocelluloses by N-methylmorpholine-N-oxide (NMMO) pretreatment: Effects of recovery and reuse of NMMO
- 2014
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 161, s. 446-450
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Tidskriftsartikel (refereegranskat)abstract
- The effects of N-methylmorpholine-N-oxide (NMMO) pretreatment on barley straw and forest residues were investigated for biogas production. The pretreatments were performed at 90 degrees C with 85% NMMO for 3-30 h. The best pretreatment conditions resulted in 100% improvement in methane yield during the subsequent digestion compared to that of the untreated lignocelluloses. Methane yields of 0.23 and 0.15 Nm(3) CH4/kg VS were obtained from barley straw and forest residues, respectively, corresponding to 88% and 83% of the theoretical yields. In addition, the effects of the pretreatment with recovered and reused NMMO was also studied over the course of five cycles. Pretreatment with recycled NMMO showed the same performance as the fresh NMMO on barley straw. However, pretreatment of forest residues with recycled NMMO resulted in 55% reduction in methane yield.
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| 5. |
- Ky, Q. M. H., et al.
(författare)
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Dimorphism of Mucor indicus: different gene expressions between yeast-like and filamentous growth
- 2013
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Ingår i: Minerva Biotecnologica. - : Edizioni Minerva Medica. - 1120-4826 .- 1827-160X. ; 25:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Aim. Mucor indicus is a zygomycetes fungus with several advantages. Its ethanol yield from hexoses rivals that of Saccharomyces cerevisiae and it is capable of producing ethanol from xylose in limited aerobic conditions. It is also able to ferment dilute acid hydrolysate and is known to be dimorphic; able to grow in both filamentous and yeast-like modes.Methods. In this study, the difference between yeast-like and filamentous cells of M. indicus was investigated using modern polymerase chain reaction (PCR) techniques. Four mRNA sequences were detected with a higher expression in the filamentous growth form than in the yeast-like, by a factor of 1.3-4.2. One of the sequences was novel and three have been detected in another species of Mucor, M. circinelloides, coding for a chitin synthase, a proteasome and a sigma 70 factor.Results and conclusion. The novel sequence exhibited the largest difference in expression and was subjected to knock-down. However, it proved to be best suited for detection of emerging growth patterns, since the knock-down had little effect on the developing growth form. With the results of this study, an important step towards understanding the difference in the dimorphic behaviour exhibited by M. indicus, as well as other members of the genus Mucor, has been taken. Potentially it could also be used as one of the tools for the control of the dimorphic behaviour of M. indicus, and other species of the Mucor genus.
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| 6. |
- Millati, Ria, 1972, et al.
(författare)
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Ethanol production from xylose and wood hydrolyzate by Mucor indicus at different aeration rates
- 2008
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Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 3:4, s. 1020-1029
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Tidskriftsartikel (refereegranskat)abstract
- The fungus Mucor indicus is able to produce ethanol from xylose as well as dilute-acid lignocellulosic hydrolyzates. The fungus completely assimilated 10 g/L xylose as the sole carbon and energy source within 32 to 65 h at an aeration rate of 0.1 to 1.0 vvm. The highest ethanol yield was 0.16 g/g at 0.1 vvm. Xylitol was formed intermediately with a maximum yield of 0.22 g/g at 0.5 vvm., but disappeared towards the end of experiments. During cultivation in a mixture of xylose and glucose, the fungus did not assimilate xylose as long as glucose was present in the medium. The anaerobic cultivation of the fungus in the hydrolyzate containing 20% xylose and 80% hexoses resulted in no assimilation of xylose but complete consumption of the hexoses in less than 15 h. The ethanol yield was 0.44 g/g. However, the xylose in the hydrolyzate was consumed when the media were aerated at 0.067 to 0.333 vvm. The best ethanol yield was 0.44 g/g at 0.067 vvm. The results of this study suggest that M. indicus hydrolyzate can be first fermented anaerobically for hexose assimilation and subsequently continued under oxygen-limited conditions for xylose fermentation.
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| 7. |
- Purwandari, F. A., et al.
(författare)
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Pretreatment of oil palm empty fruit bunch (OPEFB) by N-methylmorpholine-N-oxide (NMMO) for biogas production: Structural changes and digestion improvement
- 2013
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 128, s. 461-466
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Tidskriftsartikel (refereegranskat)abstract
- Pretreatment of OPEFB (oil palm empty fruit bunch) by NMMO (N-methylmorpholine-N-oxide) on its subsequent digestions was investigated. The pretreatments were carried out at 90 and 120 degrees C for 1, 3, and 5 h in three different modes of dissolution (by 85% NMMO solution), ballooning (79% NMMO solution), and swelling (73% NMMO solution). The total solid recovery after the pretreatment was 89-94%. The pretreatment process did not have a major impact on the composition of OPEFB, other than a reduction of ash from 5.4% up to 1.3%. The best improvement in biogas production was achieved by a dissolution mode pretreatment of OPEFB, using conditions of 85% NMMO, 3 h, and 120 degrees C. It resulted in 0.408 Nm(3)/kg VS methane yield and 0.032 Nm(3) CH4/kg VS/day initial methane production rate, which correspond in improving by 48% and 167% compared to the untreated OPEFB, respectively.
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| 8. |
- Teghammar, A., et al.
(författare)
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Techno-economic study of NMMO pretreatment and biogas production from forest residues
- 2014
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Ingår i: Applied Energy. - : Pergamon. - 0306-2619 .- 1872-9118. ; 116, s. 125-133
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Tidskriftsartikel (refereegranskat)abstract
- Biogas is nowadays getting more attention as a means for converting wastes and lignocelluloses to green fuels for cars and electricity production. The process of biogas production from N-methylmorpholine oxide (NMMO) pretreated forest residues used in a co-digestion process was economically evaluated. The co-digestion occurs together with the organic fraction of municipal solid waste (OFMSW). The process simulated the milling of the lignocelluloses, NMMO pretreatment unit, washing and filtration of the feedstock, followed by an anaerobic co-digestion, upgrading of the biogas and de-watering of the digestate. The process also took into consideration the utilization of 100,000 DW (dried weight) tons of forest residues and 200,000 DW tons of OFMSW per year. It resulted in an internal rate of return (IRR) of 24.14% prior to taxes, which might be attractive economically. The cost of the chemical NMMO treatment was regarded as the most challenging operating cost, followed by the evaporation of the washing water. Sensitivity analysis was performed on different plant size capacities, treating and digesting between 25,000 and 400,000 DW tons forest residues per year. It shows that the minimum plant capacity of 50,000 DW tons forest residues per year is financially viable. Moreover, different co-digestion scenarios were evaluated. The co-digestion of forest residues together with sewage sludge instead of OFMSW, and the digestion of forest residues only were shown to be non-feasible solutions with too low IRR. Furthermore, biogas production from forest residues was compared with the energy produced during combustion.
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| 9. |
- Westman, J., et al.
(författare)
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Improved sugar co-utilisation by encapsulation of a recombinant Saccharomyces cerevisiae strain in alginate-chitosan capsules
- 2014
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Ingår i: Biotechnology for Biofuels. - : BioMed Central Ltd.. - 1754-6834. ; 7:1, s. 102-
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Tidskriftsartikel (refereegranskat)abstract
- Background Two major hurdles for successful production of second-generation bioethanol are the presence of inhibitory compounds in lignocellulosic media, and the fact that Saccharomyces cerevisiae cannot naturally utilise pentoses. There are recombinant yeast strains that address both of these issues, but co-utilisation of glucose and xylose is still an issue that needs to be resolved. A non-recombinant way to increase yeast tolerance to hydrolysates is by encapsulation of the yeast. This can be explained by concentration gradients occuring in the cell pellet inside the capsule. In the current study, we hypothesised that encapsulation might also lead to improved simultaneous utilisation of hexoses and pentoses because of such sugar concentration gradients. Results In silico simulations of encapsulated yeast showed that the presence of concentration gradients of inhibitors can explain the improved inhibitor tolerance of encapsulated yeast. Simulations also showed pronounced concentration gradients of sugars, which resulted in simultaneous xylose and glucose consumption and a steady state xylose consumption rate up to 220-fold higher than that found in suspension culture. To validate the results experimentally, a xylose-utilising S. cerevisiae strain, CEN.PK XXX, was constructed and encapsulated in semi-permeable alginate-chitosan liquid core gel capsules. In defined media, encapsulation not only increased the tolerance of the yeast to inhibitors, but also promoted simultaneous utilisation of glucose and xylose. Encapsulation of the yeast resulted in consumption of at least 50% more xylose compared with suspended cells over 96-hour fermentations in medium containing both sugars. The higher consumption of xylose led to final ethanol titres that were approximately 15% higher. In an inhibitory dilute acid spruce hydrolysate, freely suspended yeast cells consumed the sugars in a sequential manner after a long lag phase, whereas no lag phase was observed for the encapsulated yeast, and glucose, mannose, galactose and xylose were utilised in parallel from the beginning of the cultivation. Conclusions Encapsulation of xylose-fermenting S. cerevisiae leads to improved simultaneous and efficient utilisation of several sugars, which are utilised sequentially by suspended cells. The greatest improvement is obtained in inhibitory media. These findings show that encapsulation is a promising option for production of second-generation bioethanol.
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| 10. |
- Ylitervo, Päivi, 1983, et al.
(författare)
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Membrane bioreactors' potential for ethanol and biogas production: a review
- 2013
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Ingår i: Environmental Technology (United Kingdom). - : Informa UK Limited. - 1479-487X .- 0959-3330. ; 34:13-14, s. 1711-1723
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Tidskriftsartikel (refereegranskat)abstract
- Companies developing and producing membranes for different separation purposes, as well as the market for these, have markedly increased in numbers over the last decade. Membrane and separation technology might well contribute to making fuel ethanol and biogas production from lignocellulosic materials more economically viable and productive. Combining biological processes with membrane separation techniques in a membrane bioreactor (MBR) increases cell concentrations extensively in the bioreactor. Such a combination furthermore reduces product inhibition during the biological process, increases product concentration and productivity, and simplifies the separation of product and/or cells. Various MBRs have been studied over the years, where the membrane is either submerged inside the liquid to be filtered, or placed in an external loop outside the bioreactor. All configurations have advantages and drawbacks, as reviewed in this paper. The current review presents an account of the membrane separation technologies, and the research performed on MBRs, focusing on ethanol and biogas production. The advantages and potentials of the technology are elucidated.
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