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Reymond H, Vitas S, Vernuccio S, von Rohr PR. Reaction Process of Resin-Catalyzed Methyl Formate Hydrolysis in Biphasic Continuous Flow. Ind Eng Chem Res 2017. [DOI: 10.1021/acs.iecr.6b04820] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Seidel CM, Pielhop T, Studer MH, Rudolf von Rohr P. The influence of the explosive decompression in steam-explosion pretreatment on the enzymatic digestibility of different biomasses. Faraday Discuss 2017; 202:269-280. [DOI: 10.1039/c7fd00066a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
For the production of second generation biofuels from lignocellulosic biomass, pretreatment of the biomass feedstock is necessary to overcome its recalcitrance in order to gain fermentable sugars. Due to many reasons, steam-explosion pretreatment is currently the most commonly used pretreatment method for lignocellulosic biomass on a commercial scale [S. Brethauer and M. H. Studer, CHIMIA, 2015, 69, 572–581]. In contrast to others, we showed that the explosive decompression at the end of this pretreatment step can have a positive influence on the enzymatic digestibility of softwood, especially in combination with high enzyme dosages [T. Pielhop, et al., Biotechnology for Biofuels, 2016, 9, 152]. In this study, the influence of the explosive decompression on the enzymatic digestibility of hardwood and herbaceous plants was systematically studied. Beech and corn stover were pretreated under different pretreatment conditions and enzymatically hydrolysed with different enzyme dosages. The maximum enhancement of the digestibility of corn stover was 16.53% after a 2.5 min pretreatment step at 15 barg steam pressure. For beech, a maximum relative enhancement of 58.29% after a 10 min pretreatment step at 15 barg steam pressure could be reached. With this, we show that the explosive decompression can also enhance the enzymatic cellulose digestibility of hardwood and herbaceous plants.
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Altheimer M, Becker D, D'Aleo FP, Rudolf von Rohr P. Flow regime and liquid–solid mass transfer investigation in a designed porous structure using electrochemical micro-probes. Chem Eng Sci 2016. [DOI: 10.1016/j.ces.2016.06.066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Butscher D, Van Loon H, Waskow A, Rudolf von Rohr P, Schuppler M. Plasma inactivation of microorganisms on sprout seeds in a dielectric barrier discharge. Int J Food Microbiol 2016; 238:222-232. [PMID: 27668570 DOI: 10.1016/j.ijfoodmicro.2016.09.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 08/31/2016] [Accepted: 09/11/2016] [Indexed: 11/29/2022]
Abstract
Fresh produce is frequently contaminated by microorganisms, which may lead to spoilage or even pose a threat to human health. In particular sprouts are considered to be among the most risky foods sold at retail since they are grown in an environment practically ideal for growth of bacteria and usually consumed raw. Because heat treatment has a detrimental effect on the germination abilities of sprout seeds, alternative treatment technologies need to be developed for microbial inactivation purposes. In this study, non-thermal plasma decontamination of sprout seeds is evaluated as a promising option to enhance food safety while maintaining the seed germination capabilities. In detail, investigations focus on understanding the efficiency of non-thermal plasma inactivation of microorganisms as influenced by the type of microbial contamination, substrate surface properties and moisture content, as well as variations in the power input to the plasma device. To evaluate the impact of these parameters, we studied the reduction of native microbiota or artificially applied E. coli on alfalfa, onion, radish and cress seeds exposed to non-thermal plasma in an atmospheric pressure pulsed dielectric barrier discharge streamed with argon. Plasma treatment resulted in a maximum reduction of 3.4 logarithmic units for E. coli on cress seeds. A major challenge in plasma decontamination of granular food products turned out to be the complex surface topology, where the rough surface with cracks and crevices can shield microorganisms from plasma-generated reactive species, thus reducing the treatment efficiency. However, improvement of the inactivation efficiency was possible by optimizing substrate characteristics such as the moisture level and by tuning the power supply settings (voltage, frequency) to increase the production of reactive species. While the germination ability of alfalfa seeds was considerably decreased by harsh plasma treatment, enhanced germination was observed under mild conditions. In conclusion, the results from this study indicate that cold plasma treatment represents a promising technology for inactivation of bacteria on seeds used for sprout production while preserving their germination properties.
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Pielhop T, Amgarten J, von Rohr PR, Studer MH. Steam explosion pretreatment of softwood: the effect of the explosive decompression on enzymatic digestibility. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:152. [PMID: 27453727 PMCID: PMC4957380 DOI: 10.1186/s13068-016-0567-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 07/12/2016] [Indexed: 05/02/2023]
Abstract
BACKGROUND Steam explosion pretreatment has been examined in many studies for enhancing the enzymatic digestibility of lignocellulosic biomass and is currently the most common pretreatment method in commercial biorefineries. The information available about the effect of the explosive decompression on the biochemical conversion is, however, very limited, and no studies prove that the latter is actually enhanced by the explosion. Hence, it is of great value to discern between the effect of the explosion on the one hand and the steaming on the other hand, to identify their particular influences on enzymatic digestibility. RESULTS The effect of the explosive decompression in the steam explosion pretreatment of spruce wood chips on their enzymatic cellulose digestibility was studied systematically. The explosion had a high influence on digestibility, improving it by up to 90 % compared to a steam pretreatment without explosion. Two factors were identified to be essentially responsible for the effect of the explosion on enzymatic digestibility: pretreatment severity and pressure difference of the explosion. A higher pretreatment severity can soften up and weaken the lignocellulose structure more, so that the explosion can better break up the biomass and decrease its particle size, which enhances its digestibility. In particular, increasing the pressure difference of the explosion leads to more defibration, a smaller particle size and a better digestibility. Though differences were found in the micro- and nanostructure of exploded and non-exploded biomass, the only influence of the explosion on digestibility was found to be the macroscopic particle size reduction. Steam explosion treatments with a high severity and a high pressure difference of the explosion lead to a comparatively high cellulose digestibility of the-typically very recalcitrant-softwood biomass. CONCLUSIONS This is the first study to show that explosion can enhance the enzymatic digestibility of lignocellulosic biomass. If the enhancing effect of the explosion is thoroughly exploited, even very recalcitrant biomass like softwood can be made enzymatically digestible.
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Butscher D, Zimmermann D, Schuppler M, Rudolf von Rohr P. Plasma inactivation of bacterial endospores on wheat grains and polymeric model substrates in a dielectric barrier discharge. Food Control 2016. [DOI: 10.1016/j.foodcont.2015.09.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Vernuccio S, von Rohr PR, Medlock J. General Kinetic Modeling of the Selective Hydrogenation of 2-Methyl-3-butyn-2-ol over a Commercial Palladium-Based Catalyst. Ind Eng Chem Res 2015. [DOI: 10.1021/acs.iecr.5b03424] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Butscher D, Schlup T, Roth C, Müller-Fischer N, Gantenbein-Demarchi C, Rudolf von Rohr P. Inactivation of microorganisms on granular materials: Reduction of Bacillus amyloliquefaciens endospores on wheat grains in a low pressure plasma circulating fluidized bed reactor. J FOOD ENG 2015. [DOI: 10.1016/j.jfoodeng.2015.03.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Zenklusen A, Walser S, Rudolf von Rohr P. Influence of ligament shape and thickness on vortex shedding in highly porous structures. Chem Eng Sci 2015. [DOI: 10.1016/j.ces.2014.12.028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Schuler MJ, Rothenfluh T, Rudolf von Rohr P. “Stagnation flow heat transfer of confined, impinging hot water jets under supercritical pressures”. J Supercrit Fluids 2015. [DOI: 10.1016/j.supflu.2015.01.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Schuler MJ, Rothenfluh T, Stathopoulos P, Brkic D, Meier T, Rudolf von Rohr P. Simulating Supercritical Water Jets with a Variable Turbulent Prandtl Number. Chem Eng Technol 2014. [DOI: 10.1002/ceat.201300661] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Schuler MJ, Rothenfluh T, Rudolf von Rohr P. Numerical analysis of penetration lengths in submerged supercritical water jets. J Supercrit Fluids 2013. [DOI: 10.1016/j.supflu.2013.07.017] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Assmann N, Werhan H, Ładosz A, Rudolf von Rohr P. Supercritical extraction of lignin oxidation products in a microfluidic device. Chem Eng Sci 2013. [DOI: 10.1016/j.ces.2013.05.032] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Tidona B, Koppold C, Bansode A, Urakawa A, Rudolf von Rohr P. CO2 hydrogenation to methanol at pressures up to 950bar. J Supercrit Fluids 2013. [DOI: 10.1016/j.supflu.2013.03.027] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Rothenfluh T, Schuler MJ, Rudolf von Rohr P. Experimental heat transfer study on impinging, turbulent, near-critical water jets confined by an annular wall. J Supercrit Fluids 2013. [DOI: 10.1016/j.supflu.2013.03.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Schuler MJ, Rothenfluh T, Rudolf von Rohr P. Simulation of the thermal field of submerged supercritical water jets at near-critical pressures. J Supercrit Fluids 2013. [DOI: 10.1016/j.supflu.2012.12.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Bansode A, Tidona B, von Rohr PR, Urakawa A. Impact of K and Ba promoters on CO2hydrogenation over Cu/Al2O3catalysts at high pressure. Catal Sci Technol 2013. [DOI: 10.1039/c2cy20604h] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Assmann N, Kaiser S, Rudolf von Rohr P. Supercritical extraction of vanillin in a microfluidic device. J Supercrit Fluids 2012. [DOI: 10.1016/j.supflu.2012.03.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Butscher A, Bohner M, Roth C, Ernstberger A, Heuberger R, Doebelin N, Rudolf von Rohr P, Müller R. Printability of calcium phosphate powders for three-dimensional printing of tissue engineering scaffolds. Acta Biomater 2012; 8:373-85. [PMID: 21925623 DOI: 10.1016/j.actbio.2011.08.027] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2011] [Revised: 08/12/2011] [Accepted: 08/31/2011] [Indexed: 11/24/2022]
Abstract
Three-dimensional printing (3DP) is a versatile method to produce scaffolds for tissue engineering. In 3DP the solid is created by the reaction of a liquid selectively sprayed onto a powder bed. Despite the importance of the powder properties, there has to date been a relatively poor understanding of the relation between the powder properties and the printing outcome. This article aims at improving this understanding by looking at the link between key powder parameters (particle size, flowability, roughness, wettability) and printing accuracy. These powder parameters are determined as key factors with a predictive value for the final 3DP outcome. Promising results can be expected for mean particle size in the range of 20-35 μm, compaction rate in the range of 1.3-1.4, flowability in the range of 5-7 and powder bed surface roughness of 10-25 μm. Finally, possible steps and strategies in pushing the physical limits concerning improved quality in 3DP are addressed and discussed.
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Voitl T, von Rohr PR. Reply to “Comments on ‘Demonstration of a Process for the Conversion of Kraft Lignin into Vanillin and Methyl Vanillate by Acidic Oxidation in Aqueous Methanol’”. Ind Eng Chem Res 2010. [DOI: 10.1021/ie100313f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Voitl T, Rohr PRV. Demonstration of a Process for the Conversion of Kraft Lignin into Vanillin and Methyl Vanillate by Acidic Oxidation in Aqueous Methanol. Ind Eng Chem Res 2009. [DOI: 10.1021/ie901293p] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Fries DM, von Rohr PR. Liquid mixing in gas–liquid two-phase flow by meandering microchannels. Chem Eng Sci 2009. [DOI: 10.1016/j.ces.2008.11.019] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Voitl T, Rudolf von Rohr P. Oxidation of lignin using aqueous polyoxometalates in the presence of alcohols. CHEMSUSCHEM 2008; 1:763-9. [PMID: 18688829 DOI: 10.1002/cssc.200800050] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
A novel approach has been developed in order to use Kraft lignin as a renewable resource for the production of chemicals. The concept is based on the use of polyoxometalates as reversible oxidants and on the use of radical scavengers, which prevent lignin fragments from repolymerizing. The oxidation of Kraft lignin, which is a potential source of functionalized phenols, by H3PMo12O40 in water yields a relatively small amount of monomeric species detected by GC-MS. The addition of methanol to the reaction resulted in an increase in the yield of monomeric products by a factor of up to 15. Vanillin and methyl vanillate are the main products obtained, in a maximum yield of 5 wt % based on dry Kraft lignin. Methanol plays a decisive role in the prevention of repolymerization by reducing lignin-lignin condensation reactions. Furthermore, it is proposed that methanol generates small amounts of .CH3 and CH3O. radicals through the acid-catalyzed formation of dimethyl ether which couple with lignin fragments.
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Urakawa A, Trachsel F, von Rohr PR, Baiker A. On-chip Raman analysis of heterogeneous catalytic reaction in supercritical CO2: phase behaviour monitoring and activity profiling. Analyst 2008; 133:1352-4. [DOI: 10.1039/b808984c] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Studer M, Rudolf von Rohr P. Novel membrane bioreactor: Able to cope with fluctuating loads, poorly water soluble VOCs, and biomass accumulation. Biotechnol Bioeng 2007; 99:38-48. [PMID: 17570707 DOI: 10.1002/bit.21532] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Biological waste gas treatment is an attractive method for controlling air emissions of volatile organic compounds (VOCs). Microorganisms degrade the VOCs to harmless products such as carbon dioxide (CO(2)), biomass and water. In spite of the advantages, significant unresolved challenges remain for biological waste gas treatment. Fluctuating loads in waste gas streams, especially of VOCs with low water solubility, can often not be satisfactorily removed. Concentration peaks leave the reactor virtually untreated, while periods without VOCs in the waste gas lead to starvation of the bacteria. Furthermore, bioreactors are often subject to clogging due to biomass accumulation. In the current work, a flat sheet membrane bioreactor was developed which was able to buffer fluctuating loads of toluene, our model compound, by absorption in silicone oil prior to degradation and which continuously removed and discharged excess biomass from the reactor. The absorption and the biodegradation were both membrane based. An inverse bacterial biofilm developed on the membrane, which separated the culture medium from the absorbent. The culture medium was constantly passed along the biofilm, introducing shear stresses on the surface and thereby removing excess, inactive biomass. The toluene surface elimination capacity was virtually independent of the gas flow rate for the tested steady-state conditions and reached a maximum of 0.6 g m(-2) h(-1). Experiments with fluctuating inlet mass flow rates of toluene confirmed the excellent buffering capability of the set-up. The reactor was successfully operated for 162 days without clogging.
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