Showing papers on "Citric acid published in 2019"

Carbon Dots from Citric Acid and its Intermediates Formed by Thermal Decomposition

Abstract: Thermal decomposition of citric acid is one of the most common synthesis methods for fluorescent carbon dots; the reaction pathway is, however, quite complex and the details are still far from being understood. For instance, several intermediates form during the process and they also give rise to fluorescent species. In the present work, the formation of fluorescent C-dots from citric acid has been studied as a function of reaction time by coupling infrared analysis, X-ray photoelectron spectroscopy, liquid chromatography/mass spectroscopy (LC/MS) with the change of the optical properties, absorption and emission. The reaction intermediates, which have been identified at different stages, produce two main emissive species, in the green and blue, as also indicated by the decay time analysis. C-dots formed from the intermediates have also been synthesised by thermal decomposition, which gave an emission maximum around 450 nm. The citric acid C-dots in water show short temporal stability, but their functionalisation with 3-aminopropyltriethoxysilane reduces the quenching. The understanding of the citric acid thermal decomposition reaction is expected to improve the control and reproducibility of C-dots synthesis.

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.

Systems metabolic engineering for citric acid production by Aspergillus niger in the post-genomic era.

Abstract: Citric acid is the world’s largest consumed organic acid and is widely used in beverage, food and pharmaceutical industries. Aspergillus niger is the main industrial workhorse for citric acid production. Since the release of the genome sequence, extensive multi-omic data are being rapidly obtained, which greatly boost our understanding of the citric acid accumulation mechanism in A. niger to a molecular and system level. Most recently, the rapid development of CRISPR/Cas9 system facilitates highly efficient genome-scale genetic perturbation in A. niger. In this review, we summarize the impact of systems biology on the citric acid molecular regulatory mechanisms, the advances in metabolic engineering strategies for enhancing citric acid production and discuss the development and application of CRISPR/Cas9 systems for genome editing in A. niger. We believe that future systems metabolic engineering efforts will redesign and engineer A. niger as a highly optimized cell factory for industrial citric acid production.

Isolation and Characterization of the High Silicate and Phosphate Solubilizing Novel Strain Enterobacter ludwigii GAK2 that Promotes Growth in Rice Plants

Abstract: Silicon (Si) and phosphorus (P) are beneficial nutrient elements for plant growth. These elements are widely used in chemical fertilizers despite their abundance in the earth’s crust. Excessive use of chemical fertilizers is a threat to sustainable agriculture. Here, we screened different Si and P solubilizing bacterial strains from the diverse rice fields of Daegu, Korea. The strain with high Si and P solubilizing ability was selected and identified as Enterobacter ludwigii GAK2 through 16S rRNA gene sequence analysis. The isolate GAK2 produced organic acids (citric acid, acetic acid, and lactic acid), indole-3-acetic acid, and gibberellic acid (GA1, GA3) in Luria-Bertani media. In addition, GAK2 inoculation promoted seed germination in a gibberellin deficient rice mutant Waito-C and rice cultivar ‘Hwayoungbyeo’. Overall, the isolate GAK2 increased root length, shoot length, fresh biomass, and chlorophyll content of rice plants. These findings reveal that E. ludwigii GAK2 is a potential silicon and phosphate bio-fertilizer.

Physicochemical Properties, Cytotoxicity, and Antioxidative Activity of Natural Deep Eutectic Solvents Containing Organic Acid

Abstract: Natural deep eutectic solvents (NADES) may be considered ‘designer solvents’ due to their numerous structural variations and the possibility of tailoring their physicochemical properties. Prior to their industrial application, characterization of NADES is essential, including determination of their physicochemical properties, cytotoxicity, and antioxidative activity. The most important physicochemical properties of eight prepared NADES (choline chloride:malic acid, proline:malic acid, choline chloride:proline:malic acid, betaine:malic acid, malic acid:glucose, malic acid:glucose:glycerol, choline chloride:citric acid, and betaine:citric acid) were measured as functions of temperature and water content. In general, the structure of prepared NADES greatly influences their physical properties, which could be successfully modified and adjusted by addition of water. All tested NADES were absolutely benign and noncorrosive for investigated steel X6CrNiTi18-10. Furthermore, cytotoxicity of prepared solvents was assessed toward three human cell lines (HEK-293T, HeLa, and MCF-7 cells), and antioxidative activity was measured by the Oxygen Radical Absorbance Capacity (ORAC) method. With regard to cell viability, all tested NADES containing carboxylic acid could be classified as practically harmless and considered environmentally safe. The ORAC values indicated that the tested NADES displayed antioxidative activity.

Production of Added-Value Chemical Compounds through Bioconversions of Olive-Mill Wastewaters Blended with Crude Glycerol by a Yarrowia lipolytica Strain

Abstract: Olive mill wastewaters (OMW) are the major effluent deriving from olive oil production and are considered as one of the most challenging agro-industrial wastes to treat. Crude glycerol is the main by-product of alcoholic beverage and oleochemical production activities including biodiesel production. The tremendous quantities of glycerol produced worldwide represent a serious environmental challenge. The aim of this study was to assess the ability of Yarrowia lipolytica strain ACA-DC 5029 to grow on nitrogen-limited submerged shake-flask cultures, in crude glycerol and OMW blends as well as in media with high initial glycerol concentration and produce biomass, cellular lipids, citric acid and polyols. The rationale of using such blends was the dilution of concentrated glycerol by OMW to (partially or fully) replace process tap water with a wastewater stream. The strain presented satisfactory growth in blends; citric acid production was not affected by OMW addition (Citmax~37.0 g/L, YCit/Glol~0.55 g/g) and microbial oil accumulation raised proportionally to OMW addition (Lmax~2.0 g/L, YL/X~20% w/w). Partial removal of color (~30%) and phenolic compounds (~10% w/w) of the blended media occurred. In media with high glycerol concentration, a shift towards erythritol production was noted (Erymax~66.0 g/L, YEry/Glol~0.39 g/g) simultaneously with high amounts of produced citric acid (Citmax~79.0 g/L, YCit/Glol~0.46 g/g). Fatty acid analysis of microbial lipids demonstrated that OMW addition in blended media and in excess carbon media with high glycerol concentration favored oleic acid production.

Citric Acid Production by Aspergillus niger from Agro-Industrial By-Products: Molasses and Chicken Feather Peptone

Abstract: Citric acid is a commercially important organic acid with a wide range of applications. To reduce the cost of producing citric acid, sugar beet molasses and chicken feather peptone (CFP) were used as the sole carbon and nitrogen sources, respectively for submerged citric acid biosynthesis using Aspergillus niger. To improve the citric acid production, the parental isolate of A. niger MO-25 was improved by mutation using ethidium bromide. Citric acid production using molasses was significantly affected by CFP concentrations (1–6 g/L). The maximum citric acid concentration was determined at 4 g/L CFP and 168 h. When CFP compared to commercial peptones (casein and bacto), the highest citric acid production was obtained with CFP. Furthermore, the addition of KH2PO4 (0.15 g/L) enhanced citric acid production (68.8 g/L). These results suggested that sugar beet molasses supplemented with CFP as organic nitrogen and mineral salt sources could be utilized for the economical and efficient production of citric acid. This is the first study to investigate the influence of CFP for citric acid production.

Citric acid enhances the physical properties, cytocompatibility and osteogenesis of magnesium calcium phosphate cement.

Abstract: In recent years, the magnesium phosphate cements showed impressive advantages for their setting property, mechanical strength, and resorption rate in laboratory investigation. While it remained a big challenge to develop the magnesium phosphate cements with ideal self-setting properties, sufficient mechanical strength, excellent biocompatibility, and osteoinductivity for clinical application. In our work, we prepared the magnesium calcium phosphate cement (MCPC) using the MgO, KH2P2O4, and Ca(H2PO4)2 particles with the citric acid added. The citric acid was adopted to modify the setting time and compressive strength of the MCPC, which were investigated by the X-ray diffractometer and scanning electron microscopy. The cytocompatibility and osteoinductivity of the modified cements were evaluated by the MC3T3-E1 cells proliferation and morphology, alkaline phosphatase assay, alizarin red staining and western blot assay. The results demonstrated that the citric acid modified MCPC was featured of satisfactory setting time, ideal mechanical strength, good cytocompatibility and osteoinductivity, indicating its potential application for bone regeneration.

Citric acid and itaconic acid accumulation: variations of the same story?

Abstract: Citric acid production by Aspergillus niger and itaconic acid production by Aspergillus terreus are two major examples of technical scale fungal fermentations based on metabolic overflow of primary metabolism. Both organic acids are formed by the same metabolic pathway, but whereas citric acid is the end product in A. niger, A. terreus performs two additional enzymatic steps leading to itaconic acid. Despite of this high similarity, the optimization of the production process and the mechanism and regulation of overflow of these two acids has mostly been investigated independently, thereby ignoring respective knowledge from the other. In this review, we will highlight where the similarities and the real differences of these two processes occur, which involves various aspects of medium composition, metabolic regulation and compartmentation, transcriptional regulation, and gene evolution. These comparative data may facilitate further investigations of citric acid and itaconic acid accumulation and may contribute to improvements in their industrial production.