Citric acid

About: Citric acid is a research topic. Over the lifetime, 17745 publications have been published within this topic receiving 277125 citations. The topic is also known as: citrate & H3cit.

Improvement of bacterial cellulose production by manipulating the metabolic pathways in which ethanol and sodium citrate involved.

Abstract: Nowadays, bacterial cellulose has played more and more important role as new biological material for food industry and medical and industrial products based on its unique properties. However, it is still a difficult task to improve the production of bacterial cellulose, especially a large number of byproducts are produced in the metabolic biosynthesis processes. To improve bacterial cellulose production, ethanol and sodium citrate are added into the medium during the fermentation, and the activities of key enzymes and concentration of extracellular metabolites are measured to assess the changes of the metabolic flux of the hexose monophosphate pathway (HMP), the Embden–Meyerhof–Parnas pathway (EMP), and the tricarboxylic acid cycle (TCA). Our results indicate that ethanol functions as energy source for ATP generation at the early stage of the fermentation in the HMP pathway and the supplementation of ethanol significantly reduces glycerol generation (a major byproduct). While in the EMP pathway, sodium citrate plays a key role, and its supplementation results in the byproducts (mainly acetic acid and pyruvic acid) entering the gluconeogenesis pathway for cellulose synthesis. Furthermore, by adding ethanol and sodium citrate, the main byproduct citric acid in the TCA cycle is also reduced significantly. It is concluded that bacterial cellulose production can be improved by increasing energy metabolism and reducing the formation of metabolic byproducts through the metabolic regulations of the bypasses.

Photocatalytic degradation of citric acid under different conditions: TiO2 heterogeneous photocatalysis against homogeneous photolytic processes promoted by Fe(III) and H2O2

Abstract: Degradation of citric acid (Cit) at relatively high concentrations by photocatalysis over TiO2 under air bubbling and near UV-light was tested under different conditions. The reaction was improved by addition of H2O2, Fe(III) or both. Minor amounts of H2O2 were effective to enhance the oxidation and the mineralization. H2O2 addition impacts more on the initial rate, while the effect of Fe(III) is more important after prolonged irradiation. The kinetic profiles were analyzed and compared, and the best ratio of reagents was found (1:1:1 H2O2/Cit/Fe molar ratio). However, a lower amount of Fe (1:1:0.2 H2O2/Cit/Fe ratio) was also effective. Similar experiments under the optimal conditions in the absence of TiO2 were performed for comparison. When both H2O2 and Fe(III) were present, the behavior with and without TiO2 was very similar. So far, 3-oxoglutaric acid was detected as a reaction intermediate. A mechanistic analysis is initiated to explain some features of these complex systems.

Ester crosslinking to improve wet performance of paper using multifunctional carboxylic acids, butanetetracarboxylic and citric acid

Abstract: Butanetetracarboxylic acid and citric acid are two multifunctional carboxylic acid that have potential use in formaldehyde-free durable press finishing of fabrics. In this study, these acids were investigated as cellulose crosslinking agents for modifying the wet performance of paperboard. The crosslink reaction involves the formation of two ester linkages per acid molecule to the hydroxylrich surface of cellulose to form a covalently linked structure that restricts the swelling of water. All wet properties of ester crosslinked paperboard were significantly improved, as were dimensional stability and creep performance; two important dry properties–stretch and tensile energy absorption–were seriously decreased. For specialty products where water-soak properties of stiffness, dimensional stability and reduced creep are important and dry toughness is not important, ester crosslinking may be a solution to material needs. Ester crosslinking eliminates the problems that are encountered with formaldehyde crosslinking. It also affords a paddry-cure process that is compatible with paper machine operation and yet has the advantage of a delayed cure option.