China 
Africa 
Explore chapters and articles related to this topic
Photoelectrochemical Ammonia Production
Published in Anirban Das, Gyandshwar Kumar Rao, Kasinath Ojha, Photoelectrochemical Generation of Fuels, 2023
Arpna Jaryal, Anjali Verma, Kamalakannan Kailasam
Nessler’s reagent is a solution of potassium tetraiodomercurate(II) (K2[HgI4]) and potassium hydroxide (KOH). The purpose of KOH(aq) is to stabilize the complex of tetraiodomercurate(II) and to transform NH4+ ions from the solution into free NH3. In alkaline conditions, iodine and mercury ions react with ammonia to form reddish-brown complex (equation 6.4). This complex absorbs at a wavelength of 420 nm. The concentration of ammonia is directly proportional to the absorbance of this complex without any interfering agent. High concentration of ammonia leads to the precipitation of the reddish-brown complex further affecting its accurate estimation. Therefore, proper dilution is a necessary aspect of this quantification technique. 2[HgI4]2−+NH3+3OH−→Hg2ONH2I+7I−+2H2O
l-Asparaginase
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
The direct nesslerization assay is the most common and frequently used method. Here, the ammonia released is the byproduct during the hydrolysis of the substrate l-asparagine by the action of l-asparaginase. The protocol proceeds by incubating enzyme-substrate mixture at 37°C for a certain period. After the completion of the incubation period, the reaction is terminated by trichloroacetic acid. The mixture is thereafter centrifuged to settle down the coagulated protein (by TCA) and get a clear supernatant. The supernatant is mixed with a particular volume of Nessler’s reagent. Nessler’s reagent, which is an aqueous solution of potassium iodide, mercuric chloride and potassium hydroxide, reacts with ammonia that leads to change in color of the supernatant from colorless to yellow/brown. The reaction between ammonia and Nessler’s reagent is given by the following equation:
Isolation of bacteria with plant growth-promoting properties from microalgae-bacterial flocs produced in high-rate oxidation ponds
Published in Environmental Technology, 2023
Wiya L. Masudi, Yinka Titilawo, Taobat A. Keshinro, A. Keith Cowan
Ammonia production activity was assessed using peptone water (PW) at pH 7.2 with Nessler’s reagent as the indicator [39,40]. Inoculants were added to 50 mL of PW and incubated on a rotary shaker for 3 d at 30°C. Thereafter, 30 mL from each sample was centrifuged (18,900 × g for 10 min), and 5 mL of supernatant from each reacted with 0.5 mL Nessler’s reagent, and the mixture was allowed to stand at room temperature for 5 min for maximum development of brown colour. Nessler’s reagent was prepared fresh by suspending it in 100 mL of distilled water, 10 g of HgCl2, 7 g of KI, and 16 g of NaOH. Quantification of NH3 was by spectrophotometric analysis at 430 nm followed by interpolation from a standard curve for NH4Cl [41] and data expressed as NH4Cl equivalents.
Lactic acid wastewater treatment by photosynthetic bacteria and simultaneous production of protein and pigments
Published in Environmental Technology, 2022
Fan Meng, Meng Peng, Xintian Wang, Guangming Zhang
Wastewater sample was centrifuged at 11,000 rpm for 10 min to separate the PSB cells and supernatant. The supernatant was removed and tested for COD and contents according to the APHA method [18]. The COD was determined by the dichromated method. The method is to add a known amount of potassium dichromate solution to the water sample, use silver salt as catalyst in strong acid medium, after boiling and reflux, titrate the unreduced potassium dichromate in the water sample with ammonium ferrous sulphate, and calculate the mass concentration of oxygen consumed from the amount of potassium dichromate consumed. The water quality determination of ammonia nitrogen was determined by the Nessler reagent method. The basic solution of mercuric iodide and potassium iodide reacts with ammonia, then form a light yellow-brown colloidal compound. The chroma is directly proportional to the content of ammonia nitrogen. The sediment was used for biomass measurement and value-added substances analysis. The biomass was dried in an electric oven (SX-300, Shangdong Jihua Instrument Inc., China) and weighted with a Mettler Toledo MS104S analytic balance. The pH was measured with a pH meter (phs-3c, INESA, Shanghai, China) and DO concentration was measured with a DO meter (YSI 550A, USA).
Production, optimization, purification, characterization, and anti-cancer application of extracellular L-glutaminase produced from the marine bacterial isolate
Published in Preparative Biochemistry & Biotechnology, 2020
Hanaa Orabi, Esmail El-Fakharany, Eman Abdelkhalek, Nagwa Sidkey
The enzyme activity in the culture supernatant was assayed according to the procedure of Imada et al.[15] L-asparagine hydrolysis level was assayed by determining the ammonia released using the prepared Nessler’s reagent; 5 g KI titrated 25% HgI2 (Fluka Biochemika, Buchs, Switzerland) followed by adding 45 mL of 50% KOH and then complete volume to 100 mL with distilled water. A mixture of 1.5 mL of 0.04 M L-glutamine (Sigma-Aldrich, St. Louis, MO) in 0.05 M tris-HCl (pH 8.2) and 0.5 mL of enzyme extract incubated in water bath 37 °C for 30 min and then 0.5 mL of 1.5 M trichloroacetic acid (TCA, Sigma-Aldrich, St. Louis, MO) was added to stop the reaction solution followed by centrifugation at 10,000 rpm for 7 min. Then the ammonia released in the reaction was measured colorimetrically by adding 0.2 mL of Nessler’s reagent into samples tubes containing 0.1 mL of supernatant and 3.7 mL of distilled water and incubated for 20 min at room temperature, then the absorbance was read at 450 nm. The L-glutaminase enzyme activity was defined as an international unit (IU), where; one 1 U defined as the concentration of enzyme required to produce 1 μmol of ammonia per min under the proper conditions of the assay.