| 1. |
- Dedes, Grigorios, et al.
(author)
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Conversion of organosolv pretreated hardwood biomass into 5-hydroxymethylfurfural (HMF) by combining enzymatic hydrolysis and isomerization with homogeneous catalysis
- 2021
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In: Biotechnology for Biofuels. - : Springer Nature. - 1754-6834. ; 14
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Journal article (peer-reviewed)abstract
- Background: Over the last few years, valorization of lignocellulosic biomass has been expanded beyond the production of second-generation biofuels to the synthesis of numerous platform chemicals to be used instead of their fossil-based counterparts. One such well-researched example is 5-hydroxymethylfurfural (HMF), which is preferably produced by the dehydration of fructose. Fructose is obtained by the isomerization of glucose, which in turn is derived by the hydrolysis of cellulose. However, to avoid harsh reaction conditions with high environmental impact, an isomerization step towards fructose is necessary, as fructose can be directly dehydrated to HMF under mild conditions. This work presents an optimized process to produce fructose from beechwood biomass hydrolysate and subsequently convert it to HMF by employing homogeneous catalysis.Results: The optimal saccharification conditions were identified at 10% wt. solids loading and 15 mg enzyme/gsolids, as determined from preliminary trials on pure cellulose (Avicel® PH-101). Furthermore, since high rate glucose isomerization to fructose requires the addition of sodium tetraborate, the optimum borate to glucose molar ratio was determined to 0.28 and was used in all experiments. Among 20 beechwood solid pulps obtained from different organosolv pretreatment conditions tested, the highest fructose production was obtained with acetone (160 °C, 120 min), reaching 56.8 g/100 g pretreated biomass. A scale-up hydrolysis in high solids (25% wt.) was then conducted. The hydrolysate was subjected to isomerization eventually leading to a high-fructose solution (104.5 g/L). Dehydration of fructose to HMF was tested with 5 different catalysts (HCl, H3PO4, formic acid, maleic acid and H-mordenite). Formic acid was found to be the best one displaying 79.9% sugars conversion with an HMF yield and selectivity of 44.6% and 55.8%, respectively.Conclusions: Overall, this work shows the feasibility of coupling bio- and chemo-catalytic processes to produce HMF from lignocellulose in an environmentally friendly manner. Further work for the deployment of biocatalysts for the oxidation of HMF to its derivatives could pave the way for the emergence of an integrated process to effectively produce biobased monomers from lignocellulose.
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| 2. |
- Kalogiannis, Konstantinos, et al.
(author)
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Attack Impact and Misbehavior Detection in Vehicular Platoons
- 2022
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In: Proceedings of the 15th ACMConference on Security and Privacy in Wireless and Mobile Networks (WiSec’22). - New York, USA : ACM Digital Library. ; , s. 45-59
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Conference paper (peer-reviewed)abstract
- Cooperative Adaptive Cruise Control (CACC), a promising Vehicular Ad-hoc Network (VANET) application, automates transportation and improves efficiency. Vehicles form a platoon, following a leader, with their controllers automatically adjusting velocity, based on messages by other vehicles, to keep appropriate distances for safety. Towards deploying secure CACC, several proposals in academia and standardization leave significant questions unanswered. Thwarting adversaries is hard: cryptographic protection ensures access control (authentication and authorization) but falsified kinematic information by faulty insiders (platoon members with credentials, even the platoon leader) can cause platoon instability or vehicle crashes. Filtering out such adversarial data is challenging (computational cost and high false positive rates) but, most important, state-of-the-art misbehavior detection algorithms completely fail during platoon maneuvering. In this paper, we systematically investigate how and to what extent controllers for existing platooning applications are vulnerable, mounting a gamut of attacks, ranging from falsification attacks to jamming and collusion; including two novel attacks during maneuvering. We show how the existing middle-join and leave processes are vulnerable to falsification or 'privilege escalation' attacks. We mitigate such vulnerabilities and enable vehicles joining and exiting from any position (middle-join and middle-exit). We propose a misbehavior detection system that achieves an F1 score of ≈87 on identifying attacks throughout the lifetime of the platoon formation, including maneuvers. Our cyberphysical simulation framework can be extended to assess any other driving automation functionality in the presence of attackers.
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| 3. |
- Kalogiannis, Konstantinos G, et al.
(author)
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Acid Assisted Organosolv Delignification of Beechwood and Pulp Conversion towards High Concentrated Cellulosic Ethanol via High Gravity Enzymatic Hydrolysis and Fermentation
- 2018
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In: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 23:7
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Journal article (peer-reviewed)abstract
- Background: Future biorefineries will focus on converting low value waste streams to chemical products that are derived from petroleum or refined sugars. Feedstock pretreatment in a simple, cost effective, agnostic manner is a major challenge.Methods: In this work, beechwood sawdust was delignified via an organosolv process, assisted by homogeneous inorganic acid catalysis. Mixtures of water and several organic solvents were evaluated for their performance. Specifically, ethanol (EtOH), acetone (AC), and methyl- isobutyl- ketone (MIBK) were tested with or without the use of homogeneous acid catalysis employing sulfuric, phosphoric, and oxalic acids under relatively mild temperature of 175 °C for one hour.Results: Delignification degrees (DD) higher than 90% were achieved, where both AC and EtOH proved to be suitable solvents for this process. Both oxalic and especially phosphoric acid proved to be good alternative catalysts for replacing sulfuric acid. High gravity simultaneous saccharification and fermentation with an enzyme loading of 8.4 mg/gsolids at 20 wt.% initial solids content reached an ethanol yield of 8.0 w/v%.Conclusions: Efficient delignification combining common volatile solvents and mild acid catalysis allowed for the production of ethanol at high concentration in an efficient manner
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| 4. |
- Kalogiannis, Konstantinos G., et al.
(author)
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Aromatics from Beechwood Organosolv Lignin through Thermal and Catalytic Pyrolysis
- 2019
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In: Energies. - : MDPI. - 1996-1073. ; 12:9
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Journal article (peer-reviewed)abstract
- Biomass fractionation, as an alternative to biomass pretreatment, has gained increasing research attention over the past few years as it provides separate streams of cellulose, hemicellulose, and lignin. These streams can be used separately and can provide a solution for improving the economics of emerging biorefinery technologies. The sugar streams are commonly used in microbial conversions, whereas during recent years lignin has been recognized as a valuable compound as it is the only renewable and abundant source of aromatic chemicals. Successfully converting lignin into valuable chemicals and products is key in achieving both environmental and economic sustainability of future biorefineries. In this work, lignin retrieved from beechwood sawdust delignification pretreatment via an organosolv process was depolymerized with thermal and catalytic pyrolysis. ZSM-5 commercial catalyst was used in situ to upgrade the lignin bio-oil vapors. Lignins retrieved from different modes of organosolv pretreatment were tested in order to evaluate the effect that upstream pretreatment has on the lignin fraction. Both thermal and catalytic pyrolysis yielded oils rich in phenols and aromatic hydrocarbons. Use of ZSM-5 catalyst assisted in overall deoxygenation of the bio-oils and enhanced aromatic hydrocarbons production. The oxygen content of the bio-oils was reduced at the expense of their yield. Organosolv lignins were successfully depolymerized towards phenols and aromatic hydrocarbons via thermal and catalytic pyrolysis. Hence, lignin pyrolysis can be an effective manner for lignin upgrading towards high added value products
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| 5. |
- Kalogiannis, Konstantinos G., et al.
(author)
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OxiOrganosolv : A novel acid free oxidative organosolv fractionation for lignocellulose fine sugar streams
- 2020
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In: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 313
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Journal article (peer-reviewed)abstract
- The valorization of lignocellulosic biomass towards the production of value-added products requires an efficient pretreatment/fractionation step. In this work we present a novel, acid-free, mildly oxidative organosolv delignification process -OxiOrganosolv- which employs oxygen gas to depolymerize and remove lignin. The results demonstrate that the OxiOrganosolv process achieved lignin removal as high as 97% in a single stage, with a variety of solvents; it was also efficient in delignifying both beechwood (hardwood) and pine (softwood), a task in which organosolv pretreatments have failed in the past. Minimal amounts of sugar degradation products were detected, while cellulose recovery was ~100% in the solid pulp. Enzymatic hydrolysis of pulps showed >80 wt% cellulose conversion to glucose. Overall, the OxiOrganosolv pretreatment has significant advantages, including high delignification efficiency of hardwood and softwood biomass, absence of acid homogeneous catalysis and all corresponding challenges involved, and close to zero losses of sugars to degradation products.
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| 6. |
- Kalogiannis, Konstantinos G., et al.
(author)
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Pyrolysis of lignin with 2DGC quantification of lignin oil : Effect of lignin type, process temperature and ZSM-5 in situ upgrading
- 2015
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In: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 0165-2370 .- 1873-250X. ; 115, s. 410-418
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Journal article (peer-reviewed)abstract
- Thermal and catalytic pyrolysis of various types of lignin and their influence on the yield and the quality of the produced lignin oil were studied. Lignins originated from a mixture of pine and spruce wood (softwood), a mixture of birch and aspen wood (hardwood) and Eucalyptus Urograndis. High degree of deoxygenation of the bio-oil and maximum yield of value-added chemicals were the main targets of this work. 2DGC-ToFMS analysis was used for the qualitative and quantitative characterization of the lignin oils. Softwood lignin was found to be the most attractive feedstock and high yields of a mixture of phenolic compounds were detected in all cases. High char production was also evident for all types of lignins accounting for almost 50% of the original feedstock. The use of a commercial ZSM-5 catalyst was extremely beneficial for the process, enhancing deoxygenation at higher oil yields compared to thermal pyrolysis. Depending on the nature of the lignin, guaiacyl or syringyl groups were dominant in the oils and it was found that process optimization, involving lignin, catalyst selection and temperature could significantly improve the process efficiency.
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| 7. |
- Kalogiannis, Konstantinos, et al.
(author)
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Vulnerability Analysis of Vehicular Coordinated Maneuvers
- 2023
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In: Proceedings. - : Institute of Electrical and Electronics Engineers Inc.. ; , s. 11-20
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Conference paper (peer-reviewed)abstract
- Intelligent Transport Systems (ITS) latest standardization efforts focus on a Maneuver Coordination Service (MCS), for automated vehicles to cooperatively perform maneuvers. The goal is to avoid degrading to lower levels of automation, i.e., human input for maneuvering, e.g., when an obstacle ahead needs to be avoided. MCS-equipped vehicles communicate with nearby vehicles that are possibly affected by the impending maneuver, to establish that a maneuver can safely take place. An MCS-equipped vehicle that misbehaves can be catastrophic: transmitting falsified MCS messages or preventing their reception can mislead victim vehicles into aborting a maneuver, being delayed and, worse even, collide. In this work, we investigate the robustness of existing Maneuver Coordination Protocols (MCPs) and analyze the effect of falsification and jamming attacks. Our analysis shows an increased probability for neck injuries,i.e., whiplash, and potentially more severe injuries. As a first step towards thwarting attacks targeting MCPs, we extendMCPs to take into account on-board vehicle sensors, along with MCP messaging, before committing to a maneuver. Our results demonstrate the MCP vulnerability, the improvement thanks to the sensors, and the need to further improve MCP security. We conclude with a road-map towards a resilient MCS.
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| 8. |
- Karnaouri, Anthi, et al.
(author)
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Utilization of lignocellulosic biomass towards the production of omega-3 fatty acids by the heterotrophic marine microalga Crypthecodinium cohnii
- 2020
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In: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 303
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Tidskriftsartikel (refereegranskat)abstract
- Omega-3 fatty acids have become a commodity of high nutritional and commercial value; intensive fishing and its environmental and social cost has led researchers to seeking alternative more sustainable ways of producing them. Heterotrophic microalgae such as Crypthecodinium cohnii, a marine dinoflagellate, have the ability to utilize various substrates and accumulate high amounts of docosahexaenoic acid (DHA). In this work, a mild oxidative organosolv pretreatment of beechwood pulps was employed that allowed up to 95% of lignin removal in a single stage, thus yielding a cellulose-rich solid fraction. The enzymatic hydrolysates were evaluated for their ability to support the growth and lipid accumulation of C. cohnii in batch and fed-batch cultures; the results verified the successful microalgae growth, while DHA reached up to 43.5% of the cell’s total lipids. The proposed bioprocess demonstrated the utilization of non-edible biomass towards high added value food supplements in a sustainable and efficient manner.
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| 9. |
- Katsimpouras, Constantinos, et al.
(författare)
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Acetone/water oxidation of corn stover for the production of bioethanol and prebiotic oligosaccharides
- 2018
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Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 270, s. 208-215
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Tidskriftsartikel (refereegranskat)abstract
- Ethanol production at high-gravity promise to achieve concentrations over the threshold for an economical distillation process and concurrently reduce water consumption. However, a persisting limitation is the poor mass transfer conditions resulting in low ethanol yields and concentrations. Hereby, the combination of an acetone/water oxidation pretreatment process (AWO) with a liquefaction/saccharification step, using a free-fall mixer, before simultaneous saccharification and fermentation (SSF) can realize ethanol concentrations of up to ca. 74 g/L at a solids content of 20 wt.%. The free-fall mixer achieved a biomass slurry’s viscosity reduction by 87 % after only 2 h of enzymatic saccharification, indicating the efficiency of the mixing system. Furthermore, the direct enzymatic treatment of AWO pretreated corn stover (CS) by a GH11 recombinant xylanase, led to the production of xylooligosaccharides (XOS) with prebiotic potential and the removal of insoluble fibers of hemicellulose improved the glucose release of AWOCS by 22 %.
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