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Enantioselective Catalysts
Published in Alvin B. Stiles, Theodore A. Koch, Catalyst Manufacture, 2019
Alvin B. Stiles, Theodore A. Koch
The synthesis of (R)-4-phenyl-2-hydroxybutyric acid as an intermediate for the production of benazepril, an angiotensin enzyme inhibitor, is an example of heterogeneous en-antioselective catalysis. The synthesis using a platinum on aluminum catalyst modified with 10,11-dihydrocinchonidine is reported to have been scaled to the 200-kg range for commercial production. Investigation of the reaction variables showed that platinum is superior to rhodium while palladium and ruthenium catalysts give low activity and selectivity. Several closely related modifiers were tested and showed only limited enantioselectivity. Variation in solvent composition appeared to have a minor effect. The modifier concentration was considered with a “ligand-accelerated” reaction and an equilibrium sorption of modifier on the platinum surface.
Water Characteristics
Published in Paul N. Cheremisinoff, Handbook of Water and Wastewater Treatment Technology, 2019
Methods are used to determine such parameters as, for example, BOD, COD, and SS. Hitherto most analyses for organic constituents have been made by conventional titrimetric and calorimetric procedures and, after suitable concentration and separation, by long-established chromatographic methods. Examples are amino acids by reaction with higher fatty acids by reversed phase column chromatography. More use is being made of gas-liquid chromatography of aqueous solutions for volatile fatty acids and also of infrared spectroscopy for degradation products of alkylbenzene sulfonates (ABS) and for poly-β- hydroxybutyric acid in sewage microorganisms. The wet combustion method for organic carbon has been replaced by high-temperature catalytic oxidation and determination of the carbon dioxide formed by a nondespersive infrared method. Bacterial numbers have been determined by most probable numbers (MPN) or plate counts, and protozoa have been counted by direct microscopic observation.
Polymeric Materials Obtained through Biocatalysis
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
Florin Dan Irimie, Csaba Paizs, Monica Ioana Tosa
The degree of polymerization of polyesters obtained from hydroxyacids is generally low and depends on carbon chain length. It was noticed that for the lipase from Candida antarctica, 10-hydroxydecanoic acid was close to optimum length, as monomers with shorter and longer carbon chains (4-hydroxybutyric acid, dl-2-hydroxybutyric acid, glycolic acid, and 16-hydroxyhexadecanoic acid) failed to polymerize.
Effect of transient organic load and aeration changes to pollutant removal and extracellular polymeric substances
Published in Environmental Technology, 2023
Weiqing Jiang, Xingrong Yao, Fan Wang, Yajing Li, Suiyi Zhu, Dejun Bian
PS increments were positively correlated with anaerobic phosphorus release and TP removal, and PN increments were positively correlated with aerobic phosphorus uptake. Li et al. found a positive correlation between PS and poly-β-hydroxybutyric acid (PHA) accumulation [63], with lower PS increments resulting in lower PHA accumulation and consequently lower anaerobic phosphorus release rates. The positive correlation between PN increment and aerobic phosphorus uptake may be related to the role of EPS in biosorption for phosphorus removal, making the level of PHA in the anaerobic phase not the only key factor affecting the efficiency of subsequent aerobic phosphorus uptake [64]. PN was found to have more adsorption sites than other components in EPS, to be involved in ion transport and to play a more important role in adsorption [65,66]. Thus the aerobic phosphorus uptake rate decreased with decreasing PN increments during the transient organic load shock. The decrease in EPS increments led to a decrease in TP removal, and as PS was the main component of EPS in the organic load shock, the correlation between PS increments and TP removal was even higher, showing a decrease in TP removal with decreasing PS increments.
Developments in enzyme and microalgae based biotechniques to remediate micropollutants from aqueous systems—A review
Published in Critical Reviews in Environmental Science and Technology, 2022
Zeba Usmani, Minaxi Sharma, Tiit Lukk, Yevgen Karpichev, Vijay Kumar Thakur, Vivek Kumar, Abdelmounaaim Allaoui, Abhishek Kumar Awasthi, Vijai Kumar Gupta
Even though the usage of redox mediators results in a more efficient process, it often causes a change in the direction of the reaction, which can lead to alternative products based on the reaction mechanism. For instance, the addition of mediators to laccase changed their action toward IBU, KET and NPX from being nonselective to selective (Nguyen et al., 2017). Daassi et al. (2016) used laccase from Coriolopsis gallica to remediate BPA and reported two different pathways with and without HBT as mediator. While the former resulted in pyroglutamic and tartaric acid, the latter yielded β-hydroxybutyric acid.
Serum metabolomic adaptations following a 12-week high-intensity interval training combined to citrulline supplementation in obese older adults
Published in European Journal of Sport Science, 2023
Layale Youssef, Sylvère Durand, Fanny Aprahamian, Deborah Lefevre, Mélanie Bourgin, Maria Chiara Maiuri, Maude Dulac, Guy Hajj-Boutros, Vincent Marcangeli, Fanny Buckinx, Eva Peyrusqué, José A. Morais, Pierrette Gaudreau, Gilles Gouspillou, Guido Kroemer, Mylène Aubertin-Leheudre, Philippe Noirez
For other metabolic pathways (amino acid, nucleic acid, leucine and BCAA metabolisms), 2-hydroxybutyric acid decreased in the HIIT-PLA group. Homoserine significantly decreased while 2-aminoadipic acid and guanosine significantly increased in the HIIT-CIT group. In both HIIT-PLA and HIIT-CIT groups, 2-oxovaleric acid significantly decreased.