| 1. |
- Al-Rudainy, Basel, et al.
(författare)
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From lab-scale to on-site pilot trials for the recovery of hemicellulose by ultrafiltration: Experimental and theoretical evaluations
- 2020
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Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 250
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Tidskriftsartikel (refereegranskat)abstract
- Spent sulfite liquor (SSL) is a byproduct of the sulfite pulping process of wood. SSL usually contains monosugars and lignosulfonates, which are fermented to produce ethanol and dried to generate lignosulfonate salts. However, the SSL that was used in this work was derived from the first step of a 2-step sulfite pulping process of softwood under mild pulping conditions in the first stage of cooking. The resulting SSL contained polymeric hemicelluloses, which are not used today but have many potential applications. The up-concentration of this SSL had been performed on a lab scale by ultrafiltration. However, the pilot-scale ultrafiltration of hemicellulose-rich sodium-based SSL has not been reported. In this study, the operating conditions for the lab-scale concentration of hemicellulose-rich, sodium-based SSL were examined in a pilot-scale membrane filtration unit. The permeate flux and retention of products were lower in the pilot equipment compared with the lab-scale setup, perhaps related to the lower Reynolds number and shear rate in the former, as indicated by simulations of computational fluid dynamics. The pilot equipment also ran at a higher volume reduction compared with the lab-scale system, which could explain the difference in flux and retention. The effects of fouling and cleaning were also determined, wherein an alkaline cleaning step (pH 11) for 1 h was sufficient to remove foulants and maintain a stable average flux of 88 L/m2h and the nonchanging retention of products.
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| 2. |
- Al-Rudainy, Basel, et al.
(författare)
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Hemicellulose Recovery from Spent-Sulfite-Liquor: Lignin Removal by Adsorption to Resins for Improvement of the Ultrafiltration Process
- 2020
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Ingår i: Molecules. - : MDPI AG. - 1420-3049. ; 25:15
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Tidskriftsartikel (refereegranskat)abstract
- In this work, three polymeric resins were examined as alternatives for the separation of hemicellulose and lignin. The aim was to remove the lignin from spent-sulfite-liquor (SSL) prior to ultrafiltration, producing a hemicellulose-rich retentate with high purity, and increase the capacity of the membrane filtration. The lignin in the SSL was sulfonated; thus, two of the resins were anion exchangers and 1 was hydrophobic. The data from the equilibrium studies and adsorption kinetics were fitted to established models, and the results were interpreted based on these observations. The strongly basic anion exchanger performed best with regard to lignin removal. The adsorption followed the Sips isotherm, indicating that the process was cooperative with chemisorption as the main reaction between the adsorbate and adsorbent based on the kinetics. Regeneration of the adsorbent was also possible, wherein 100 g/L NaCl was sufficient to recover 98% of the lignin. The lignin removal had a positive effect on the ultrafiltration process, in which the flux increased by 38% and the extent of separation between the hemicellulose and lignin rose from 17% to 59%.
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| 3. |
- Bulkan, Gülru
(författare)
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Fungi-Based Biorefinery : Valorization of industrial residuals and techno-economic evaluation
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sustainable development of society and industry is necessary for a safer future that is being challenged by environmental pollution, climate change, and scarcity of food and nutrition. Materials considered as waste can be converted into value-added products and energy, hence regained to the economy. Filamentous fungi are saprophytic microorganisms that show great potential for bioconversion of organic waste materials into a wide range of products, including ethanol, enzymes, fungal biomass, and organic acids. In this study, industrial residuals from bioethanol plants (thin stillage), agro-industrial residuals (oat husks), and fruit-processing residuals were considered as potential substrates for filamentous fungi. Different filamentous fungi species were investigated due to their edibility and ability to produce ethanol. The aim of this study was to investigate 1) the feasibility of a biorefinery concept and contribution of fungal products to the process economy, 2) the valorization of oat husks in the fungal biorefinery and its contribution to the process economy, and 3) the effect of bioactive compounds existing in fruit residuals on filamentous fungi in a synthetic medium.Bioconversion of thin stillage into value-added products, e.g., additional ethanol produced by filamentous fungi and edible fungal biomass for various feed/food markets, improved the process economy of a conventional bioethanol plant. Techno-economic analysis was carried out with Aspen Plus® and Aspen Process Economic Analyzer®. The economy of the conventional bioethanol plant was improved to 76% and 5.6-fold higher net present value when the fungal product was sold as fish feed and human food, respectively. When the fungal product was sold as human food, Aspergillus oryzae was more advantageous than Neurospora intermedia. It is possible to integrate lignocellulosic material into the fungi-based biorefinery and produce additional products, e.g., lignin and fungal biomass as feed/food products. Several scenarios for integrating organosolv pretreatment into the biorefinery were investigated. When protein-rich biomass was sold as feed and food, 71% and 7.9-fold higher net present value was obtained, respectively, compared to the conventional ethanol plant. Similarly, other materials, e.g., fruit residuals, can be valorized through the fungal biorefinery. However, bioactive compounds in fruit residuals have antimicrobial effects; therefore, it is essential to assess the sensitivity of fungi toward them for efficient processes. In addition to the fungi species utilized in thin stillage and oat husk valorization, two other industrially important fungi, Rhizopus oligosporus and A. niger, were tested against 10 bioactive compounds with antimicrobial properties (octanol, ellagic acid, (-)-epicatechin, quercetin, betanin, ascorbic acid, limonene, hexanal, car-3-ene, and myrcene). The bioactive compounds were added to a synthetic medium to reach final concentrations of 2.4, 24 and 240 mg/L, within their natural concentration in fruit/fruit residuals. A. oryzae, A. niger and N. intermedia were inhibited by octanol, while the latter fungus was also inhibited by D-Limonene at 240 mg/L. On the other hand, R. oligosporus was resistant to inhibitory compounds and increased the biomass yield. The highest change in biomass yield was in the presence of ellagic acid with up to a 4-fold increase. Ethanol and lactic acid yields were increased 38% and 30% in the presence of ellagic acid and betanin, respectively. Similarly, the existence of quercetin and ellagic acid, ascorbic acid, and hexanal increased the biomass yield of A. niger up to 28%.These studies can contribute to developing efficient and feasible biorefineries, in which filamentous fungi convert the industrial residuals into value-added products.
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| 4. |
- Jonsdottir Glaser, Sara, et al.
(författare)
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Fractionation of sugar beet pulp polysaccharides into component sugars and pre-feasibility analysis for further valorisation
- 2024
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Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 14:3, s. 3575-3588
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Tidskriftsartikel (refereegranskat)abstract
- Sugar beet pulp (SBP) is a by-product formed in large amounts during the production of refined sugar and is currently used as a low-cost feed for livestock. The dry SBP comprises largely three polysaccharides (75–85%), cellulose, hemicellulose and pectin, whose component sugars constitute potential valuable feedstock for producing building blocks for chemicals and materials. In the present study, a simple and integrated process for the fractionation of SBP polysaccharides into streams enriched with corresponding sugars is developed. Initial screening of several pectinase preparations (from Novozymes) for the treatment of dry SBP (at initial pH 4.0, 50 °C) showed Pectinase ME to release the maximum amount of galacturonic acid (GalU) along with high amounts of arabinose (Ara). On the other hand, subjecting the SBP to acid hydrolysis using 0.64 M sulphuric acid at 80 °C was relatively selective in solubilising mainly Ara (71.3% of the initial content), and the subsequent treatment with Pectinase ME solubilised 68.5% of the initial GalU content. Treatment of the residual solid fraction with cellulases released 81.9% of the original glucose content. Size-exclusion chromatography revealed the presence of oligomers ranging from dimers to pentamers in the acid and pectinase hydrolysates. Mass-balance based process analysis of 1000 kgdry/h SBP biorefinery using the three-stage fractionation of sugars and further valorization to arabitol, mucic acid and levulinic acid, respectively, indicated the potential economic feasibility and value addition of SBP, which is currently sold at 200 US$/t as animal feed. Recycling of water and catalysts would be important for reducing waste generation and improving environmental performance.
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| 5. |
- Jonsdottir Glaser, Sara, et al.
(författare)
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Wheat bran fractionation : Effect of steam explosion and hydrotropic extraction conditions on the recovery of sugars and lignin
- 2023
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Ingår i: Industrial Crops and Products. - : Elsevier BV. - 0926-6690. ; 195
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Tidskriftsartikel (refereegranskat)abstract
- Wheat bran, a major by-product of wheat processing, contains several valuable components that can serve as a potential feedstock for chemical production. This study presents a multiple-stage fractionation method, involving steam explosion and hydrotropic extraction, which were investigated with the goal of separating the main structural bran components: starch, protein, hemicelluloses, lignin, and cellulose. With prior de-starching and de-proteination, acid-catalysed steam explosion (STEX1: 218 °C, 8 min, 0.05 wt% H2SO4) solubilised up to 97% of the arabinoxylans. Higher monosaccharide yields arising from hemicelluloses were observed in the de-starched and de-proteinated bran than in untreated bran prior to steam treatment. Subsequent treatment using the 40% w/w hydrotrope solution, sodium xylene sulfonate (SXS), at 170 °C for 1 h (HEX1) showed lignin recovery of up to 42.6% from the steam-exploded bran, which was higher than 25.1% lignin recovery from the de-starched, de-proteinated and steam exploded bran. The lignin recovery values were slightly underestimated as some lignin ends up in the wash, which proved difficult to quantify. Finally, glucose monomer release during cellulose hydrolysis occurred most rapidly in the bran material that had undergone prior treatments of de-starching, de-proteination, steam explosion and hydrotropic treatment, with complete hydrolysis in less than 24 h for the de-starched, de-proteinated, steam exploded for both STEX1 and STEX3 (219 °C, 0.10 wt%, 14 min) and hydrotropically treated (HEX1). The selective release of wheat bran components in separate stages of the wheat-bran fractionating scheme provides a platform for further valorisation of each component into commercially relevant products. Structural elucidation of the recovered wheat bran lignin using 2D HSQC NMR revealed that oxidised syringyl (S′) units increased from 13.2 units per 100 C2 aromatic group (Ar) in bran without prior treatment, to 16.9 units/100 Ar in steam exploded bran and 18.2 units/100 Ar in de-starched, de-proteinated and steam exploded bran. The change in guaicyl (G) unit frequencies as well as the oxidised G units (G′) remained low across samples. As less oxidation is desired for further lignin valorisation, the results herein offer insights on future work for utilising wheat bran lignin.
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| 6. |
- Molaverdi, Maryam, et al.
(författare)
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High efficient ethanol production from corn stover by modified mild alkaline pretreatment
- 2021
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 170, s. 714-723
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Tidskriftsartikel (refereegranskat)abstract
- Sodium carbonate pretreatment, an environmentally-friendly and efficient pretreatment, was used to improve solid-state ethanol production from corn stover (CS). To further enhance ethanol yield from the pretreated CS, especially at low enzyme loadings, a combined pretreatment, including steam and sodium carbonate pretreatments, was developed. The removal/modification of lignin by sodium carbonate pretreatment (at 100 °C for 3 h) helped to obtain high ethanol titer at high solids and low enzymes loadings. The maximum ethanol concentration was about 44 g/L, obtained after 72 h simultaneous saccharification and fermentation (SSF) of CS pretreated with sodium carbonate without mixing and prehydrolysis at 30% solid and 15 FPU/g enzyme loadings. Applying prehydrolysis and increasing the SSF time to 120 h improved ethanol concentration to 59 and 67 g/L, respectively. Steam pretreatment at 190 °C for 10 min before sodium carbonate pretreatment led to 76% increase in ethanol concentration. At the enzyme loading of only 5 FPU/g substrate, the modified pretreatment increased the ethanol concentration from 24 g/L to 41 g/L, compared with that of sodium carbonate pretreatment. The results showed that hemicellulose removal and delignification by steam and sodium carbonate pretreatment, respectively, considerably improved ethanol concentration at high solids and low enzyme loadings.
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| 7. |
- Montipó, Sheila, et al.
(författare)
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Steam Pretreatment of Rice Hulls to Release Fermentable Saccharides : An Approach to Improve Recovery of (Hemi)Cellulosic Sugars Through Multivariate Design
- 2021
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Ingår i: Rice Science. - : Elsevier BV. - 1672-6308. ; 28:5, s. 501-510
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Tidskriftsartikel (refereegranskat)abstract
- The conversion of rice hulls into fermentable saccharides was explored through steam pretreatment employing 2.5% SO2. The interaction between temperature and time was assessed by means of the response surface method to achieve optimum contents of C6-sugars in water-insoluble solids (WIS) and C5-sugars in the liquor. Pretreatment carried out at 218 °C for 2.3 min released liquor containing 55.4 g/L of sugars (29.1 g/L of xylose). In parallel, the WIS was subjected to enzymatic saccharification using different solid and enzyme loads via an experimental design: assays using 22.0% WIS and 20.0 filter paper units (FPU)/g led to 90.6 g/L of glucose, corresponding to a yield of 86.4% and an overall yield of 72.4%. The data reported are the highest ever found for such raw material, making it attractive to compete with conventional lignocellulosic biomass.
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| 8. |
- Nielsen, Fredrik, et al.
(författare)
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The effect of mixed agricultural feedstocks on steam pretreatment, enzymatic hydrolysis, and cofermentation in the lignocellulose-to-ethanol process
- 2020
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Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 10:2, s. 253-266
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Tidskriftsartikel (refereegranskat)abstract
- Second-generation fuel ethanol is typically researched using one type of raw material as feedstock. However, the variability in the supply and quality of biomass calls for an expansion of the feedstock base to ensure sufficient supply for commercial-scale production. By expanding the feedstock base and using mixtures in the conversion process, the biomass supply can be improved and associated economic risks can be hedged. However, the heterogeneity of feedstock mixtures requires conversion processes that can accommodate mixtures with no or minimal reduction in conversion efficiency compared to processing single feedstocks. In this study, the effects of using mixtures of wheat straw and corn stover on conversion efficiency and ethanol yield were investigated. The feedstocks and mixtures thereof were pretreated with dilute acid–catalysed steam pretreatment, and saccharified and cofermented using different simultaneous saccharification and cofermentation (SSCF) configurations, employing commercial cellulolytic enzymes and a xylose-fermenting strain of Saccharomyces cerevisiae. Process ethanol yields, based on total glucose and xylose in the raw material, were maximised by SSCF configurations that emphasise the saccharification efficiency over cofermentation efficiency. Ethanol concentrations exceeding 50 g L−1 and process ethanol yields of 74–78% of the theoretical maximum were achieved across the range of feedstocks and feedstock mixtures studied. The narrow range of the ethanol yields suggests that wheat straw and corn stover can be used interchangeably and mixed in the proposed lignocellulose-to-ethanol process without significant negative effects on conversion efficiency and process economics.
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| 9. |
- Novy, Vera, et al.
(författare)
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Elucidation of Changes in Cellulose Ultrastructure and Accessibility in Hardwood Fractionation Processes with Carbohydrate Binding Modules
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:17, s. 6767-6776
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Tidskriftsartikel (refereegranskat)abstract
- We have recently presented a sequential treatment method, in which steam explosion (STEX) was followed by hydrotropic extraction (HEX), to selectively fractionate cellulose, hemicellulose, and lignin in hardwood into separate process streams. However, above a treatment severity threshold, the structural alterations in the cellulose-enriched fraction appeared to restrict the enzymatic hydrolyzability and delignification efficiency. To better understand the ultrastructural changes in the cellulose, hardwood chips were treated by single (STEX or HEX) and combined treatments (STEX and HEX), and the cellulose accessibility quantified with carbohydrate-binding modules (CBMs) that bind preferentially to crystalline (CBM2a) and paracrystalline cellulose (CBM17). Fluorescent-tagged versions of the CBMs were used to map the spatial distribution of cellulose substructures with confocal laser scanning microscopy. With increasing severities, STEX increased the apparent crystallinity (CBM2a/CBM17-ratio) and overall accessibility (CBM2aH6 + CBM17) of the cellulose, whereas HEX demonstrated the opposite trend. The respective effects could also be discerned in the combined treatments where increasing severities further resulted in higher hemicellulose dissolution and, although initially beneficial, in stagnating accessibility and hydrolyzability. This study suggests that balancing the severities in the two treatments is required to maximize the fractionation and simultaneously achieve a reactive and accessible cellulose that is readily hydrolyzable.
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| 10. |
- Olsson, Johanna, et al.
(författare)
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An extensive parameter study of hydrotropic extraction of steam-pretreated birch
- 2023
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Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 13:5, s. 4001-4009
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Tidskriftsartikel (refereegranskat)abstract
- Efficient fractionation of lignocellulosic biomass is an important step toward the replacement of fossil-based products. However, the utilisation of all of the components in biomass requires various fractionation techniques. One promising process configuration is to apply steam explosion for the recovery of hemicelluloses and a subsequent hydrotropic extraction step for the delignification of the remaining solids. In this work, the influence of residence time, temperature and biomass loading on lignin recovery from birch using sodium xylene sulphonate as a hydrotrope was investigated. Our results show that residence time, temperature and biomass loading correlate positively with lignin extraction, but the effects of these parameters were limited. Furthermore, when steam explosion was implemented as the initial step, hydrotropic extraction could be performed even at room temperature, yielding a lignin extraction of 50%. Also, hydrothermal degradation of the material was necessary for efficient delignification with sodium xylene sulphonate, regardless of whether it occurs during steam explosion pretreatment or is achieved at high temperatures during the hydrotropic extraction.
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