Rather the Rule than the Exception: Non-Convex Pareto Sets and their Navigation in Distillation Processes

Novel algorithms for adaptive approximation and interactive navigation of Pareto sets are applied to various homogeneous distillation processes with recycle streams within an industrial flowsheet simulator. The adaptive approximation scheme shows that the Pareto set consists of both convex and non-convex regions when the product purities are maximised while minimising the total heat duties. It is illustrated how such Pareto sets can be navigated interactively using a ray tracing technique. Our results suggest that the occurrence of non-convex regions in the Pareto sets is due to recycle streams in the flowsheets and is therefore the rule rather than the exception in multi-objective optimisation of flowsheet simulations in chemical engineering.     

Fe-Zeolite as on-Site Regenerable Adsorber for Chlorohydrocarbons in Groundwater – from Laboratory to Pilot Test

This study describes the design and upscaling of an on-site regenerable adsorbent fixed bed of Fe-loaded MFI zeolite for removal of chlorinated hydrocarbons (CHCs) from contaminated groundwater from laboratory studies to pilot scale. The zeolite has an excellent adsorption performance for the hydrophilic CHCs and can be regenerated on-site by flushing with H₂O₂ to degrade adsorbed contaminants by a catalytic Fenton-like reaction. In the pilot test, the Fe-zeolite (30 kg) maintained its performance over treatment of 1470 m³ of groundwater in 12 adsorption/regeneration cycles.     

Potential of Integrated Semi-Continuous Enzymatic Synthesis and Filtration Processes for Efficiency Enhancement

Galacto-oligosaccharides (GOS), increasingly popular prebiotics, are synthesized by enzymatic conversion of lactose. Among others, the total production costs are significantly influenced by the costly enzyme. Therefore, it was investigated if the reuse and full recovery of the enzyme is feasible, followed by the development of a semi-continuous process in order to maintain a consistent high GOS yield. As a preliminary step, the enzyme-catalyzed reaction was recorded within the permissible operating parameters. It was successfully shown that steady high GOS yields can be synthesized semi-continuously within a filtration plant functioning as an enzymatic membrane reactor.     

Cell-Free Protein Synthesis for the Screening of Novel Azoreductases and Their Preferred Electron Donor

Azoreductases are potent biocatalysts for the cleavage of azo bonds. Various gene sequences coding for potential azoreductases are available in databases, but many of their gene products are still uncharacterized. To avoid the laborious heterologous expression in a host organism, we developed a screening approach involving cell-free protein synthesis (CFPS) combined with a colorimetric activity assay, which allows the parallel screening of putative azoreductases in a short time. First, we evaluated different CFPS systems and optimized the synthesis conditions of a model azoreductase. With the findings obtained, 10 azoreductases, half of them undescribed so far, were screened for their ability to degrade the azo dye methyl red. All novel enzymes catalyzed the degradation of methyl red and can therefore be referred to as azoreductases. In addition, all enzymes degraded the more complex and bulkier azo dye Brilliant Black and four of them also showed the ability to reduce p-benzoquinone. NADH was the preferred electron donor for the most enzymes, although the synthetic nicotinamide co-substrate analogue 1-benzyl-1,4-dihydronicotinamide (BNAH) was also accepted by all active azoreductases. This screening approach allows accelerated identification of potential biocatalysts for various applications.     

Does it burn? The effect of guar gum addition on ginger beer's sensory properties

Consumer demand for ginger beer has grown within the last few years due to health benefits associated with ginger consumption identified in recent studies and its low-calorie content. However, non-alcoholic ginger beer, like other non-alcoholic beverages, does not possess the same mouthfeel as its alcoholic counterparts. As such, the aim of this study was to evaluate how the addition of guar gum impacted the sensory perception, spiciness, and consumer acceptability of non-alcoholic ginger beer. Two different formulations of ginger beer were created, one without the addition of guar gum (control) and the other with 1.9 g/L guar gum added. Samples, along with carbonated water, were presented in pairs with a 20-s wait and no-rinse in between to observe sensitisation and desensitisation. The participants (n = 103) evaluated each sample for spiciness, burning or stinging sensation, along with bitterness, sweetness, sourness, overall flavour intensity, liking of flavour and mouthfeel, and overall liking. The addition of guar gum significantly impacted the perception of spiciness, burning, and stinging sensation in addition to the overall flavour intensity. The guar gum addition also negatively impacted the acceptability of the ginger beer.     

Debottlenecking of an In Vitro Enzyme Cascade Using a Combined Model- and Experiment-Based Approach

Designing a feasible in vitro enzyme cascade is a challenging task that is often preceded by optimization steps. Computational methods can increase the efficiency of the optimization process by providing a deeper insight into the system. In this study, bottlenecks of a farnesyl pyrophosphate-producing in vitro enzyme cascade were determined by a combination of in silico modeling and wet-lab experiments. ATP and the precursor-isomerizing enzyme isopentenyl diphosphate δ-isomerase were identified as limitations of the in vitro enzyme cascade.