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Publikation Continuous in situ lactic acid extraction from sweet whey fermentation broth using a tubular membrane contactor(2022) Demmelmayer, Paul; Pérez, Alan; Riedl, Wolfgang; Kienberger, MarleneBackground Whey, as the major dairy by-product, has become a severe problem for the dairy industry because its demand has decreased, while its production has increased in the past years. Since the high demand for dairy products tends to further increase, suitable routes for whey valorization are required. Whey contains valuables like lactate, but due its composition matrix, processing is challenging. The high sugar content in whey makes it a potential feedstock to produce lactic acid (LA) via microbial fermentation. Still, the known drawbacks of biotechnological LA production, such as growth inhibition by the product, the use of neutralizers, low productivity, and high overall costs of the process must be overcome. In situ LA recovering using a suitable separation technology is a potential strategy to overcome the mentioned drawbacks. In this work, the in situ LA extraction from a whey fermentation broth was evaluated. Sweet whey was used as feedstock for lactic acid production via microbial fermentation, while LA was recovered by reactive liquid-liquid extraction using a tubular membrane contactor. Method The feed material used in this work is a fermentation broth from sweet whey, which was filtered prior to extraction experiments using microfiltration. In a first series of experiments, two-phase extraction experiments were conducted in temperature controlled separation funnels, to investigate different solvent phase combinations for the lactic acid extraction. Special attention was paid to replace commonly applied fossil-based solvents with green alternatives, such as deep eutectic solvents (DES). After extraction, the extract was treated in a back-extraction step to recover LA from the solvent phase. Here, an anti-solvent, e.g. heptane or p-cymene, was used to transfer LA to the receiving phase, which was water. Afterwards the performance of reactive liquid-liquid extraction of LA using a PTFE membrane contactor was evaluated by using two potential solvent phases, namely tri-n-octyl amine (TOA) with n-decanol and a DES formed from thymol and menthol. From the experimental results the overall mass transfer coefficient was calculated based on a rigorous mass transfer model to predict the LA concentration in both phases. Finally, performance of the in situ LA recovery from sweet whey by using membrane contactor was investigated from both, experimentally and theoretically points of view. Results & Conclusion In the two-phase extraction experiments, the reactive extractants Aliquat336, TOA, trioctylphosphinoxid (TOPO), and the mixture Aliquat336/TOA were found to be most efficient with the diluents 1-decanol, limonene, and a deep eutectic solvent consisting of thymol and menthol. Especially, the DES and limonene are promising as they can be produced from renewable resources. With respect to back-extraction, heptane and p-cymene showed the highest efficiencies for transferring lactic acid into the receiving phase water. In the next step, the selected solvents were used to perform LA recovery in the tubular membrane contactor from a model aqueous solution of LA and a fermentation broth of sweet whey. The proposed technology for valorizing dairy waste through LA biotechnological production shows the feasibility to scaling it up.06 - PräsentationPublikation An “Agile” project planning course. Learning by doing in process engineering education(Elsevier, 07/2024) Riedl, Wolfgang; Brown, Andrew; Rausenberger, JuliaProcess engineering education requires a comprehensive foundation and practical application. To bridge the gap between theoretical education and market requirements, a "Project Planning Course” has been offered since 2018 as part of the MSc specialization in Chemical Engineering at the FHNW School of Life Sciences. The course didactics combines the principles of an “agile” teaching mindset and problem-based learning, which optimally support the experience of this module. Students had to work on unresolved real-world problems, make decisions based on incomplete information, and present their work in a board meeting role play with board members from industry. These situations represent typical real-world challenges for future chemical engineers. The results show that most of the students learned to cope with the unconventional teaching methodology. The students’ evaluations of the module have been very positive, especially the fact that the active participation of the students triggers the actual learning process - which means that the essential learning goal has been achieved.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Liquid extraction with immobilized liquids for product recovery from fermentation broths(Elsevier, 2022) Pérez, Alan; Gössi, Angelo; Riedl, Wolfgang; Schuur, Boelo; Fontalvo, Javier; Thatoi, Hrudayanath; Mohapatra, Sonali; Das, Swagat KumarNowadays, many fermentation chemicals are produced at an industrial scale. Numerous technological improvements have been developed and implemented to achieve high quality and quantity of fermentation products. However, several drawbacks in fermentation processes still limit their application at an industrial level. In situ product removal (ISPR) is a potential alternative to overcome the conventional drawbacks of the fermentative processes, increasing the fermentation's productivity and reducing the separation steps for recovery and purification. Currently, liquid extraction has emerged as a promising separation technology for ISPR, with immobilized liquids such as membrane-assisted extraction and microchannel liquid membrane, due to the high mass transfer rates, scalability, easy integration, and efficiency. This chapter will discuss these technologies regarding their integration into fermentative processes.04A - Beitrag SammelbandPublikation Electrochemical membrane-assisted pH-swing extraction and back-extraction of lactic acid(Elsevier, 2022) Gausmann, Marcel; Bertram, Franziska; Schuur, Boelo; Jupke, Andreas; Gössi, Angelo; Riedl, WolfgangReactive extraction of carboxylic acids such as lactic acid with tertiary amines is a state-of-the-art process but suffers strongly from reduced extraction efficiency in buffered environments like fermentation broths. In order to increase the efficiency of in-situ product removal, we here propose the combination of a membrane-assisted reactive extraction with an electrochemical pH shift. Prior to extraction in the membrane module, the fermentation broth containing the lactic acid at neutral pH is treated by anodic electrolysis to reduce the pH and thereby improve the extraction yield. Additionally, the cathodic reaction is used to increase the pH of the aqueous stream used for back-extraction of the loaded organic phase. Model solutions were used to develop a mathematical model, capable of calculating the required membrane area for in-situ extractions, considering the effect of the aqueous pH on the extraction performance. Additionally, using electrochemical pH shift, we were able to concentrate lactic acid from 1 wt% in the dilute broth to 7 wt% in the back extract.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Mass transfer analysis and kinetic modeling for process design of countercurrent membrane supported reactive extraction of carboxylic acids(Elsevier, 2021) Schuur, Boelo; Gössi, Angelo; Riedl, WolfgangCountercurrent membrane supported reactive extraction (MSRE) was studied for removal of carboxylic acids from aqueous streams with a PTFE capillary membrane. Analysis of the mass transfer rates was per- formed to support modeling of the process. Total mass transfer coefficients ranging from 2.0 10-7 to 4.0 10-7 m/s were obtained when extracting lactic acid with 20 wt% tri-N-octyl amine in 1-decanol with membrane thicknesses of 260 mm and 80 mm. The limiting mass transfer resistance in all experiments was in the membrane phase. The developed model based on mass transfer and reaction in parallel allows to predict countercurrent extraction. Experimental validation with 5, 7 and 12 m long membrane modules showed excellent accordance for two acids, validating the model simulations. Simulated membrane con- tactor lengths required for single, two and three countercurrent stages varied between 10 and 39 m/stage for lactic, mandelic, succinic, itaconic and citric acid, depending on acid, membrane, and diluent.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Membrane-supported liquid-liquid extraction. Where do we stand today?(Wiley, 02/2021) Riedl, WolfgangThanks to advances in materials science and manufacturing technology, membranes are now available for stable liquid-liquid extraction processes. Rigorous calculation models can be used to calculate the membrane areas required for a specific separation task as well as to optimize the module design. Rapid tests can determine the basic suitability and kinetic parameters. Thus, the general requirements for exploiting the specific advantages of this separation technology in technical applications are fulfilled.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation In-situ recovery of carboxylic acids from fermentation broths through membrane supported reactive extraction using membrane modules with improved stability(Elsevier, 15.06.2020) Gössi, Angelo; Burgener, Florian; Kohler, David; Urso, Alessandro; Kolvenbach, Boris; Riedl, WolfgangMembrane supported reactive extraction (MSE) coupled to back-extraction (MSBE) using a new type of Teflon (PTFE) capillary membrane contactor was studied for the in-situ removal of carboxylic acids from aqueous streams, e.g. fermentation broths. The use of microporous membranes as extraction interface helps avoiding emulsification problems, allows the use of extreme phase ratios, and protects microorganisms, as they are less affected by solvent toxicity during in-situ extractions. The use of PTFE capillary membranes is suitable for long-term use due its high chemical and thermal stability. A simple toxicity screening identified n-decanol with tri n-octyl amine (TOA) as a suitable solvent. MSE experiments were performed using membrane contactors (0.005 m2 to 0.15 m2), working with solvent to feed phase ratios down to 1:40 (mass based). The in-situ removal of lactic acid out of fermentation broths using lactobacillus plantarum led to a glucose conversion rate of 80 mol%. Additionally, a concentration factor up to 7.8 could be shown during back-extraction.01A - Beitrag in wissenschaftlicher Zeitschrift