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.

Reaction Kinetics of the Catalytic Esterification of Citric Acid with Ethanol

Abstract: Reaction kinetics are presented for the reversible esterification reaction of citric acid with ethanol to form tri-ethyl citrate via mono-ethyl and di-ethyl citrates. The reaction was studied in batch isothermal experiments, self-catalyzed homogeneously by citric acid and the formed mono- and di-ethyl citrates, and heterogeneously catalyzed by macroporous Amberlyst-15 ion-exchange resin catalyst. Experimental data were obtained between 78 and 120 °C at different mole ratios of ethanol to citric acid and catalyst concentrations up to 5 wt % ion-exchange resin. The kinetics of ethanol etherification to form di-ethyl ether were included in the investigation. Kinetic modeling was performed using a pseudo-homogeneous UNIQUAC-based activity model, taking into consideration the rate of self-catalyzed esterification and the side reaction to form diethyl ether. The activity coefficients for the tri-ethyl citrate−ethanol and tri-ethyl citrate−water binary pairs were obtained from experimental vapor−liquid equilibri...

Two-Step Separation of Chitin from Shrimp Shells Using Citric Acid and Deep Eutectic Solvents with the Assistance of Microwave.

Abstract: In this research, a two-step extraction approach was developed for chitin preparation from shrimp shells by utilizing citric acids and deep eutectic solvents (DESs), which effectively removed minerals and proteins. In the first step, minerals of shrimp shells were removed by citric acid, and the demineralization efficiency reached more than 98%. In the second step, the removal of protein was carried out using deep eutectic solvents with the assistance of microwave, and the deproteinization efficiency was more than 88%. The results of scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), and thermogravimetric analysis (TGA) showed that the quality of DES-prepared chitin was comparable to that of traditional acid/alkali-prepared chitin. These results were realized without utilizing hazardous chemicals, which are detrimental to the environment. This research indicates that a DES-based preparation approach has the potential for application in the recovery of biopolymers from natural resources.

Enhanced itaconic acid production in Aspergillus niger using genetic modification and medium optimization

Abstract: Background: Aspergillus niger was selected as a host for producing itaconic acid due to its versatile and tolerant character in various growth environments, and its extremely high capacity of accumulating the precursor of itaconic acid: citric acid. Expressing the CAD gene from Aspergillus terreus opened the metabolic pathway towards itaconic acid in A. niger. In order to increase the production level, we continued by modifying its genome and optimizing cultivation media. Results: Based on the results of previous transcriptomics studies and research from other groups, two genes : gpdA encoding the glyceraldehyde �3-dehydrogenase (GPD) and hbd1 encoding a flavohemoglobin domain (HBD) were overexpressed in A. niger. Besides, new media were designed based on a reference medium for A. terreus .T o analyze large numbers of cultures, we developed an approach for screening both fungal transformants and various media in 96-well micro-titer plates. The hbd1 transformants (HBD 2.2/2.5) did not improve itaconic acid titer while the gpdA transformant (GPD 4.3) decreased the itaconic acid production. Using 20 different media, copper was discovered to have a positive influence on itaconic acid production. Effects observed in the micro-titer plate screening were confirmed in controlled batch fermentation. Conclusions: The performance of gpdA and hbd1 transformants was found not to be beneficial for itaconic acid production using the tested cultivation conditions. Medium optimization showed that, copper was positively correlated with improved itaconic acid production. Interestingly, the optimal conditions for itaconic acid clearly differ from conditions optimal for citric- and oxalic acid production.

Identification of organic acids produced during rice straw decomposition and their role in rock phosphate solubilization

Abstract: The production of organic acids and changes during decomposition of rice straw amended with tricalcium phos phate (TCP) and Udaipur rock phosphate (URP) were studied under laboratory conditions. The organic C content of rice straw decreased and total N increased with time, resulting in a decrease in C:N ratio as the decomposition progressed. The pH decreased to acidic range in all the treatments on day 15, but became alkaline again later on. Soluble P increased at 15 days after incubation, declined later during decomposition, and was highest in the treatments containing TCP and Aspergillus awamori inoculation. Citric, oxalic, formic and maleic acids were detected during decomposition of rice straw and maximum amounts were present on day 15. Citric and oxalic acids were responsible mainly for P solubilization from TCP and URP; generally, citric acid was the most effective in P solubilization.