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.

Oxidation stability of biodiesel fuel produced from fatty wastes.

Abstract: The aim of this work was to examine possibilities to use wastes of animal fat and vegetable oil for the production of biodiesel fuel, evaluating the conformity of the product obtained to the oxidation stability requirements. The oxidation stability of rapeseed oil, linseed oil, tallow and lard fatty acid methyl esters samples and their mixtures was measured by commercial equipment Rancimat 743 applying accelerated oxidation test (Rancimat test) specified in EN 14112. It was found that fatty acid methyl esters of vegetable origin are more stable for oxidation comparing with methyl esters of animal origin. The optimal level of synthetic antioxidants such as butylated hydroxyanizole (BHA) and butylated hydroxytoluene (BHA) for stabilization of fatty acid methyl esters was determined to be 400 ppm (also using synergist – citric acid, 20% of the antioxidant quantity). Mixtures of methyl esters of animal and vegetable origin with antioxidants were more stable compared with pure products. The highest oxidation stability showed mixtures containing 80-90% of fatty acid methyl esters of animal fat and 10-20% of fatty acid methyl esters of vegetable oil with synthetic antioxidants added.

Microbiological Production of Citric and Isocitric Acids from Sunflower Oil

Abstract: Summary The growth of wild type strain Yarrowia lipolytica VKM Y-2373 and its mutant Yarrowia lipolytica N 15 as well the biosynthesis of citric and isocitric acids on sunflower oil were studied. It was indicated that cell growth was associated with the simultaneous utilization of glycerol and free fatty acids produced during oil hydrolysis. The activities of enzymes of glycerol metabolism (glycerol kinase), fatty acid assimilation enzymes of glyoxylate cycle (isocitrate lyase and malate synthase) and citric acid cycle were comparatively assayed in Y. lipolytica grown on sunflower oil, glycerol and oleic acid. Glycerol kinase and enzymes of glyoxylate cycle were active during the whole period of cell cultivation on sunflower oil. Citric acid production and a ratio between citric and isocitric acids depended on both the strain used and the medium composition. It was revealed that wild type strain Y. lipolytica VKM Y-2373 produced almost equal amounts of citric and isocitric acids at pH=4.5 and predominantly accumulated isocitric acid at pH=6.0. The mutant Y. lipolytica N1 5 produced only citric acid (150 g/L with mass yield (YCA) of 1.32 g/g). Biochemical characteristics of mutant strain Y. lipolytica N 15 were discussed.

Biodegradable packaging foam and method of preparation

Abstract: A closed cell, light weight packaging material having biodegradable properties and being formed initially from a nonmodified starch material which has been modified by reaction within an extrusion barrel with (i) a mild acid selected from the group consisting of malic acid, tartaric acid, citric acid, maleic acid and succinic acid in the presence of water and (ii) a carbonate composition to generate CO2 gas. This modified starch material has decreased molecular weight and a dominant pattern of nonuniformity of hydrogen bonding within and between starch chains, and a dominant pattern of structural randomness of the starch chains. The resultant packaging material has a closed cellular structure with a density less than 0.032 grams per cubic centimeter and with resilient properties which enable substantial return of the compressed structure to its original, expanded shape with structural integrity. Also set forth is a process for preparing this material, as well as modification for enhancing hydrophobicity.

Enhancement of uranium phytoaccumulation from contaminated soils

Abstract: Chelation and complexation of uranium (U) and soil acidification were evaluated as practical ways to solubilize, detoxify, and enhance U accumulation by plants. Sunflower (Helianthus annuus) and Indian mustard (Brassica juncea) were selected as potential U accumulators for U phytoextraction in one U mine tailing soil (469 mg U kg -1 ) and nine acid and calcareous soils (pH 4.7 to 8.1) contaminated with different rates (100 to 600 mg U(VI)kg -1 ) of uranyl nitrate (UO 2 (NO 3 ) 2 .6H 2 O). To enhance U phytoextraction, organic chelates were added to soils alone or as complexed-U forms of CDTA, DTPA, EDTA, and HEDTA, and citric and oxalic acids at rates of 1 to 25 mmol kg -1 , to soils with 4-week old seedlings. Dry matter production, U concentration in shoots and roots, and soil pH were measured. Contaminated soils were also evaluated for U desorption and by fractionation. Uranium desorption was performed with 2 to 20 mmol kg -1 of citric acid, CDTA, DTPA, and HEDTA. Uranium fractions [(exchangeable, carbonate, manganese (Mn), iron (Fe), organic, and residual)] were determined after 4 weeks of incubation. Plant dry matter production and U accumulation varied with soil contamination rate, chelate, organic acid form and rate, and soil type. The highest U concentration was in plants growing in calcareous soils and the lowest in clayey acid soils with high Fe and Mn oxides and organic matter content. Addition of citric and oxalic acids increased U accumulation and U translocation to the shoots significantly. Addition of 20 mmol of citric acid kg -1 to loamy acid soils reduced the soil pH to below 5.0 and increased U concentration in shoots to 1400 mg U kg -1 or by 150-fold, but addition of complexed-U forms had little effect on U translocation to shoots. Citric acid was the most effective chelate in desorption and plant accumulation of U. Uranium phytoacumulation was limited to acid soils with low adsorptive potential and to alkaline soils with carbonate minerals.