Showing papers by "DECHEMA published in 2020"

A multi-layered view of chemical and biochemical engineering

Abstract: The contents of this article are based on the results of discussions the corresponding author has had since 2015 with the co-authors, who are members of academia and industry in Europe, on the scope and significance of chemical and biochemical engineering as a discipline. The result is a multi-layered view of chemical and biochemical engineering where the inner-layer deals with the fundamental principles and their application; the middle-layer deals with consolidation and expansion of the principles through a combination of science and engineering, leading to the development of sustainable technologies; and the outer-layer deals with integration of knowledge and collaboration with other disciplines to achieve a more sustainable society. Through this multi-layered view several important issues with respect to education, research and practice are highlighted together with current and future challenges and opportunities.

From CO2 to Bioplastic - Coupling the Electrochemical CO2 Reduction with a Microbial Product Generation by Drop-in Electrolysis.

Abstract: CO2 has been electrochemically reduced to the intermediate formate, which was subsequently used as sole substrate for the production of the polymer polyhydroxybutyrate (PHB) by the microorganism Cupriavidus necator. Faradaic efficiencies (FE) up to 54 % have been reached with Sn-based gas-diffusion electrodes in physiological electrolyte. The formate containing electrolyte can be used directly as drop-in solution in the following biological polymer production by resting cells. 56 mg PHB L-1 and a ratio of 34 % PHB per cell dry weight were achieved. The calculated overall FE for the process was as high as 4 %. The direct use of the electrolyte as drop-in media in the bioconversion enables simplified processes with a minimum of intermediate purification effort. Thus, an optimal coupling between electrochemical and biotechnological processes can be realized.

Microbial Electrosynthesis-An Inventory on Technology Readiness Level and Performance of Different Process Variants.

Abstract: The objective of microbial electrosynthesis (MES) is to combine the advantages of electrochemistry and biotechnology in order to produce chemicals and fuels. This combination enables resource-efficient processes by using renewable raw materials and regenerative energies. In the last decade, different MES processes have been described, for example, MES based on biofilms or mediators, electro-fermentation, and secondary MES. This review compares the MES technologies with regard to the reached process performances in terms of key process indicators (i.e., coulombic efficiency (CE), product titre, productivity) and technology readiness level (TRL). Often the underlying mechanism of electron transfer in biofilm-based processes has not been elucidated and can therefore not be optimized. Similarly, technical aspects of electro-fermentation processes and processes with soluble mediators are under investigation and techno-economic assessments are missing. In contrast, the electrochemical production of microbial substrates in secondary MES or hybrid systems show high key process indicators and TRLs up to 7. In summary, the different types of MES processes offer options for today's industrial use, as well as an exciting and future-oriented technology that can be applied in a medium-term perspective.

Artificial Light-Harvesting Complexes Enable Rieske Oxygenase Catalyzed Hydroxylations in Non-Photosynthetic cells.

Abstract: In this study, we coupled a well-established whole-cell system based on E. coli via light-harvesting complexes to Rieske oxygenase (RO)-catalyzed hydroxylations in vivo. Although these enzymes represent very promising biocatalysts, their practical applicability is hampered by their dependency on NAD(P)H as well as their multicomponent nature and intrinsic instability in cell-free systems. In order to explore the boundaries of E. coli as chassis for artificial photosynthesis, and due to the reported instability of ROs, we used these challenging enzymes as a model system. The light-driven approach relies on light-harvesting complexes such as eosin Y, 5(6)-carboxyeosin, and rose bengal and sacrificial electron donors (EDTA, MOPS, and MES) that were easily taken up by the cells. The obtained product formations of up to 1.3 g L-1 and rates of up to 1.6 mm h-1 demonstrate that this is a comparable approach to typical whole-cell transformations in E. coli. The applicability of this photocatalytic synthesis has been demonstrated and represents the first example of a photoinduced RO system.

Risk Governance of Emerging Technologies Demonstrated in Terms of its Applicability to Nanomaterials

Abstract: Nanotechnologies have reached maturity and market penetration that require nano-specific changes in legislation and harmonization among legislation domains, such as the amendments to REACH for nanomaterials (NMs) which came into force in 2020. Thus, an assessment of the components and regulatory boundaries of NMs risk governance is timely, alongside related methods and tools, as part of the global efforts to optimise nanosafety and integrate it into product design processes, via Safe(r)-by-Design (SbD) concepts. This paper provides an overview of the state-of-the-art regarding risk governance of NMs and lays out the theoretical basis for the development and implementation of an effective, trustworthy and transparent risk governance framework for NMs. The proposed framework enables continuous integration of the evolving state of the science, leverages best practice from contiguous disciplines and facilitates responsive re-thinking of nanosafety governance to meet future needs. To achieve and operationalise such framework, a science-based Risk Governance Council (RGC) for NMs is being developed. The framework will provide a toolkit for independent NMs' risk governance and integrates needs and views of stakeholders. An extension of this framework to relevant advanced materials and emerging technologies is also envisaged, in view of future foundations of risk research in Europe and globally.

Coupled Electrochemical and Microbial Catalysis for the Production of Polymer Bricks.

Abstract: Power-to-X technologies have the potential to pave the way towards a future resource-secure bioeconomy as they enable the exploitation of renewable resources and CO2 . Herein, the coupled electrocatalytic and microbial catalysis of the C5 -polymer precursors mesaconate and 2S-methylsuccinate from CO2 and electric energy by in situ coupling electrochemical and microbial catalysis at 1 L-scale was developed. In the first phase, 6.1±2.5 mm formate was produced by electrochemical CO2 reduction. In the second phase, formate served as the substrate for microbial catalysis by an engineered strain of Methylobacterium extorquens AM-1 producing 7±2 μm and 10±5 μm of mesaconate and 2S-methylsuccinate, respectively. The proof of concept showed an overall conversion efficiency of 0.2 % being 0.4 % of the theoretical maximum.

Synthesis of bifunctional BaFe1−xCoxO3−y−δ(OH)y catalysts for the oxygen reduction reaction and oxygen evolution reaction

Abstract: Perovskite oxides with mixed ionic and electronic conductivities are very promising candidates for their application as energy materials related to fuel cell and metal air battery integration. In this article, we report on the systematic characterization of mixed proton and electron conducting compounds of composition BaFe1−xCoxO3−y−δ(OH)y synthesized via nebulized spray pyrolysis. Independent of the value of x, all samples BaFe1−xCoxO3−y−δ(OH)y were found to crystallize in an orthorhombic ordering/distortion variant of the perovskite type structure (space group Cmcm) and are isotypic to the border phases (x = 0 or 1) reported previously. A minimum water content was observed for the composition with x = 0.5, which increases steadily for Co or Fe richer compositions. Impedance studies show that the conductivity increases with increasing Co-content, with BaCo0.5Fe0.5O2.07(OH)0.74 showing a total electrical conductivity of 10−7 S cm−1 at 298 K, an order of magnitude higher than found for BaFeO2.33(OH)0.33. Further, bifunctional catalytic activity for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) was found for the compounds of the series as investigated in 0.1 M KOH, with BaFe0.8Co0.2O3−y−δ(OH)y possessing the best bifunctional performance parameter of ΔU = 1.10 V, which is comparable to that of other non-precious metal catalysts.

The origin of the hysteresis in cyclic voltammetric response of alkaline methanol electrooxidation

Abstract: The mechanism of the alkaline methanol electrooxidation reaction on platinum is complex and not fully understood However, a better understanding will facilitate reaching the theoretical performance of an alkaline methanol fuel cell Cyclic voltammetry is an often used method to investigate the mechanism of electrochemical reactions The cyclic voltammogram of methanol electrooxidation shows a hysteresis in potential between the oxidation peaks in the forward and backward scans The origin of this hysteresis has not been fully clarified By means of parameter variations, such as the upper potential or the starting point of the CV measurements, and by physicochemical modeling, we investigate the formation of platinum oxides as a possible cause of this behaviour The experiments show that the formation of platinum oxides is more likely to cause the hysteresis than the strongly adsorbed intermediates, which are formed during the forward scan The simulation includes the formation of platinum oxide species and supports the experimental results that the hysteresis is due to the formation and reduction of platinum oxides Besides, the simulation reveals that in the investigated potential area, different oxide forms are present

Enzymatic Oxidation of Butane to 2-Butanol in a Bubble Column

Abstract: Unspecific peroxygenases have recently gained significant interest due to their ability to catalyse the hydroxylation of non-activated C−H bonds using only hydrogen peroxide as a co-substrate. However, the development of preparative processes has so far mostly concentrated on benzylic hydroxylations using liquid substrates. Herein, we demonstrate the application of a peroxygenase for the hydroxylation of the inert, gaseous substrate butane to 2-butanol in a bubble column reactor. The influence of hydrogen peroxide feed rate and enzyme loading on product formation, overoxidation to butanone and catalytic efficiency is investigated at 200 mL scale. The process is scaled up to 2 L and coupled with continuous extraction. This setup allowed the production of 115 mmol 2-butanol and 70 mmol butanone with an overall total turnover number (TTN) of over 15.000, thereby demonstrating the applicability of peroxygenases for preparative hydroxylation of such inert, gaseous substrates at mild reaction conditions.

Biotechnological Production of Odor-Active Methyl-Branched Aldehydes by a Novel α-Dioxygenase from Crocosphaera subtropica.

Abstract: As a result of their pleasant odor qualities and low odor thresholds, iso- and anteiso-fatty aldehydes represent promising candidates for applications in flavoring preparations. A novel cyanobacter...

Investigation of monoterpenoid resistance mechanisms in Pseudomonas putida and their consequences for biotransformations

Abstract: Monoterpenoids are widely used in industrial applications, e.g. as active ingredients in pharmaceuticals, in flavor and fragrance compositions, and in agriculture. Severe toxic effects are known for some monoterpenoids making them challenging compounds for biotechnological production processes. Some strains of the bacterium Pseudomonas putida show an inherent extraordinarily high tolerance towards solvents including monoterpenoids. An understanding of the underlying factors can help to create suitable strains for monoterpenoids de novo production or conversion. In addition, knowledge about tolerance mechanisms could allow a deeper insight into how bacteria can oppose monoterpenoid containing drugs, like tea tree oil. Within this work, the resistance mechanisms of P. putida GS1 were investigated using selected monoterpenoid-hypertolerant mutants. Most of the mutations were found in efflux pump promoter regions or associated transcription factors. Surprisingly, while for the tested monoterpenoid alcohols, ketone, and ether high efflux pump expression increased monoterpenoid tolerance, it reduced the tolerance against geranic acid. However, an increase of geranic acid tolerance could be gained by a mutation in an efflux pump component. It was also found that increased monoterpenoid tolerance can counteract efficient biotransformation ability, indicating the need for a fine-tuned and knowledge-based tolerance improvement for production strain development.Key points• Altered monoterpenoid tolerance mainly related to altered activity of efflux pumps.• Increased tolerance to geranic acid surprisingly caused by decreased export activity. • Reduction of export activity can be beneficial for biotechnological conversions.

Analyzing and Engineering the Product Selectivity of a 2-Methylenebornane Synthase.

Abstract: Terpenes constitute the largest class of natural products with more than 70 000 compounds. Many different terpenes find applications in the flavor and fragrance industry or can be used as fine chem...

Fast heat treatment methods for al slurry diffusion coatings on alloy 800 prepared in air

Abstract: In the present study aluminum diffusion coatings were prepared on alloy 800H within a few minutes in air using several surface heating methods: induction heating, a natural gas burner, and a heating mat. All such methods are highly relevant for on-site applications, because they are commonly known from post welding heat-treatments. The very short (3 or 5 min) dwell times at temperatures between 700 and 1000 °C were sufficient to produce continuous diffusion coatings with all heat treatment methods. With the heating mat more of the Al-poor (Fe, Cr, Ni)Al phase is formed during diffusion treatment at 1000 °C due to the slower heating and cooling rates in comparison to the other techniques.

Origin of the Drastic Current Decay during Potentiostatic Alkaline Methanol Oxidation.

Abstract: The current production from the alkaline methanol electro-oxidation reaction does not reach a steady state on a smooth platinum catalyst under potentiostatic conditions. We investigated two possibl...

Model-Based Analysis of the Photocatalytic HCl Oxidation Kinetics over TiO2

Abstract: The kinetic modeling of photocatalytic reactions is a powerful tool for process optimization. We applied a holistic kinetic model for the gas-phase photocatalytic oxidation of HCl to Cl2 to identif...

An Electrically Rechargeable Zinc/Air Cell with an Aqueous Choline Acetate Electrolyte

Abstract: Due to the feasibility of an electrically rechargeable zinc/air cell made of a zinc foil as active material, an aqueous choline acetate (ChAcO) mixture as an electrolyte and a spinel MnCo2O4 (MCO) and NiCo2O4 (NCO) as a bi-functional oxygen catalyst was investigated in this work The 30 wt% water-containing aqueous ChAcO solution showed high contact angles close to those of KOH favoring triple-phase boundary formation in the gas diffusion electrode Conductivity and pH value of 30 wt% H2O/ChAcO amounted to 59 mS cm−1 and 108, respectively Best results in terms of reversible capacity and longevity of zinc/air cell were yielded during 100 h charge/discharge with the MnCo2O4 (MCO) air electrode polarization procedure at 100 µA cm−2 (28 mA g−1zinc) The corresponding reversible capacity amounted to 254 mAh (28% depth of discharge (DOD)) and the energy efficiency ranged from 29–54% during the first and seventh cycle within a 1500 h polarization period Maximum active material utilization of zinc foil at 100 µA cm−2 was determined to 381 mAh (42% DOD) whereas a further charging step was not possible due to irreversible passivation of the zinc foil surface A special side-by-side optical cell was used to identify reaction products of the zinc/air system during a single discharge step in aqueous ChAcO that were identified as Zn(OH)2 and ZnO by Raman analysis while no carbonate was detected

Approaches for the evaluation of future-oriented technologies and concepts in the field of water reuse and desalination

Abstract: Against the background of drastically rising global water demand and increasing pollution and overexploitation of regional water resources, the demand-driven water supply of households and industry is of central importance. Water reuse and desalination are seen as key technologies to overcome potential regional and local water shortage. In the joint projects funded by the German Federal Ministry of Education and Research (BMBF) ‘Future-oriented Technologies and Concepts to Increase Water Availability by Water Reuse and Desalination (WavE)’, evaluation approaches for analysing innovative technologies and concepts are being developed and assessed. All evaluation methods and criteria used were selected based on the decision situation at hand and the decisionmakers preferences. Based on the analysis of six multi-criteria evaluation concepts used in selected WavE projects, this paper presents a general approach for comparative multi-criteria evaluation of water reuse systems consisting of prerequisites, minimum requirements, evaluation criteria (qualitative, semi-quantitative or quantitative) and a final aggregation of results. Exemplary sets of criteria for the application in a more industrial, municipal and/or international context are presented as an aid for the application of holistic evaluation approaches for (process) concept and technology selection in the context of water reuse and desalination.