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Culture Media
Published in Maria Csuros, Csaba Csuros, Klara Ver, Microbiological Examination of Water and Wastewater, 2018
Maria Csuros, Csaba Csuros, Klara Ver
pH indicators determine whether or not an acid has been produced as an end product of the metabolism. Phenol red and bromcresol purple are the two pH indicators most frequently used in microbiological work. Phenol red appears red in basic and yellow in acidic pH, bromcresol purple is purple in basic and yellow in acidic solutions. Inoculate carbohydrate broths with the sample.Keep one tube of the carbohydrate broth uninoculated for control.Incubate the tubes at 37°C. Make observations at 24, 48, and 72 h.After each incubation period, compare each of the inoculated tubes with the control tube to determine whether growth occurred and whether acid or acid and gas were produced.If at any time during the incubation period should a fermentation tube contain both acid and gas, it is not necessary to continue incubation. The tube may be discarded after recording the result.
Blood Chemistry Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
pH fluorescence measurements can be obtained using a pH-sensitive dye, such as phenol red. The basic form of phenol red is green absorbing, and the acidic form is blue absorbing. Exciting the phenol red buffer with a green 560 nm and red 600 nm light, the ratio of intensities can be used to calculate the pH according to Equation 68.18: R=k*10[-C/(10-δ+1)]
Sensing Effects and Sensitive Polymers
Published in Gábor Harsányi, Polymer Films in Sensor Applications, 2017
pH-sensors can be fabricated directly from the acid-base indicators or from their combination. Recently, agarose, a typical polysaccharide material, was used by Hao et al. [192] instead of polyacrylamide to immobilize phenol red indicator. Phenol red in the agarose gel matrix shows almost identical optical and chemical properties to those in water. The agrose gel matrix appears to allow relatively fast proton transfer. Phenol red has a colour-change range of pH 6–8.
Applications of aged powders of spray-dried whey protein isolate and ascorbic acid in the field of food safety
Published in Drying Technology, 2023
Chao Zhong, Songwen Tan, Zelin Zhou, Xia Zhong, Timothy Langrish
Microbial contamination causes reductions in food shelf life, and it increases the possibility of food-borne illnesses. For consumers, the changed texture, flavor and color of the food may be unacceptable. To deal with this problem, some food sensors[6–8] have been developed, which also help to mitigate food waste.[9] With the help of specific reactions, food sensors may be used to indicate food quality or safety. The pH of the chemical environment for foods can be changed by microbial spoilage.[10] When food is stored, transported or distributed, a pH indicator can be used to monitor its pH condition and give information about its quality. An indicator may respond through visible color development in response to pH changes.[11,12] The pH may be detected using an indicator, and a simple, low-cost, rapid and environmentally friendly sensor is helpful.[5] In order to detect volatile compounds that are acidic or basic, changes in the visual appearance of some pH dyes may be considered. Colorimetric pH indicator dyestuffs may be used, including bromothymol blue, bromophenol blue, bromocresol purple, methyl red, bromocresol green, methyl orange, methyl yellow, phenol red.[13] As pH indicators, methyl red (MR) and bromocresol purple (BCP) are toxic.
Synthesis, characterization, structural description, TGA, micellization behavior, DNA-binding and antioxidant activity of mono-, di- and tri-nuclear Cu(II) and Zn(II) carboxylate complexes
Published in Journal of Coordination Chemistry, 2021
Muhammad Iqbal, Amir Karim, Ihsan Ullah, Muhammad Abdul Haleem, Saqib Ali, Muhammad Nawaz Tahir, Syed Mustansar Abbas
Complex 1 is synthesized by the reaction of biphenylacetic acid (7 mmol, 1.485 g) with sodium bicarbonate (7 mmol, 0.558 g) in distilled water at 60 °C. The reaction progress was monitored from color change of phenol red from yellow to blue used as indicator. Then copper sulfate (3.5 mmol, 0.558 g in 20 mL DMSO) solution was added gradually with constant stirring for 2 h at 60 °C. The desired compounds were obtained as precipitate from water mother liquor and then air-dried in shade. The dry sample was dissolved in DMSO and kept for crystallization. The crystals appeared after 20 days in the solvent, while a substantial quantity of the solvent was still there. The crystals were separated from the solvent and characterized through FTIR and X-ray crystal studies. All the reactions for 1–3 are schematically presented in Figure 1. Light blue crystals; m.p. 177–178 °C; yield (81%). FTIR (cm−1): 1595 ν(OCO)asym, 1396 ν(OCO)sym, Δν = 199, 428 ν(Cu − O). Elemental analysis: Calculated (%): C, 59.8; H, 5.29. Found (%): C, 59.5; H, 4.98.
Removal of alkalinity and metal toxicity from incinerated biomedical waste ash by using Bacillus halodurans
Published in Bioremediation Journal, 2022
Harsimranpreet Kaur, Rafat Siddique, Anita Rajor
To analyze the pH reduction capacity of the strain B. sp. KG1, the initial pH of the medium was taken to be 13. After 18 h of incubation and shaking (TCLP), the change in pH has been analyzed using a pH meter (Eutech instruments pH tutor). Figure 9 shows plot pH reduction in alkaline growth medium by strain B. sp. KG1 versus time (days). It has been observed that the pH of the medium reduced to 8.05 after 5 days. This strain showed well able to tolerate and grow at higher pH values as the OD value validates the statement. This is in line with the previous research (Kunal, Rajor, and Siddique 2016; Paavilainen, Helisto, and Korpela 1994). The reason for the sustainability of bacteria growth at such a high pH is that the pH gradient gets reversed due to high membrane potential. The inorganic carbon as the source food for the energy has reduced the carbon into acids and thus reduced the pH of the alkaline medium. The presence of carbohydrates in nutrient broth is a direct source of inorganic carbon (IC) and the growth of bacteria gets supported by it. Kunal, Rajor, and Siddique (2016) have reported that the B. sp. KG1 is proficient in producing organic acid (acetic and formic acid). These acids are capable to solubilize the complex metal cations into low pH acidolysis. The bacteria regulate the carbonate system and hence carbonates regulate the pH of the medium. Cole and Prairie (2014) reported that if the pH of the system is below 5, the IC has a very small effect on the pH change of the system and if the pH of the system is high, the IC has a positive impact on the change in pH of the system. The alkaliphilic bacteria’s growth is directly related to pH and IC of the surrounding, hence this statement supports acid production has lowered the pH of the alkaline medium. To investigate if acid production was there in the medium or not, Phenol red indicator was added to the medium. It has been observed that the phenol red color changed to orange and orange to yellow. This was a sign of acid production by the bacteria. At 3 days of incubation, the pH was lowered by 2.1 units whereas at 7 and 8 days of incubation change is zero units was observed which seems to be negligible when compared with the change in pH with other days of incubation. The results indicate that the B. sp. KG1 bacteria is highly efficient in reducing the pH of the IBWA and it can be used where the main purpose of the treatment is to reduce the pH.