Addition Of M-cresol Research Articles

Respirometric response and microbial succession of nitrifying sludge to m-cresol pulses in a sequencing batch reactor.

A nitrifying consortium was kinetically, stoichiometrically and molecularly characterized via the in situ pulse respirometric method and pyrosequencing analysis before and after the addition of m-cresol (25mgCL-1) in a sequencing batch reactor (SBR). Five important kinetic and stoichiometric parameters were determined: the maximum oxygen uptake rate, the maximum nitrification rate, the oxidation yield, the biomass growth yield, and the substrate affinity constant. An inhibitory effect was observed in the nitrification process with a recovery of this by up to eight SBR cycles after m-cresol was added to the system. However, full recovery of the nitrification process was not observed, as the maximum oxygen uptake rate was 25% lower than that of the previous operation without m-cresol addition. Furthermore, the pyrosequencing analyses of the nitrifying consortium after the addition of only two pulses of 25mgCL-1 m-cresol showed an important microbial community change represented by a decrease in the nitrifying populations and an increase in the populations degrading phenolic compounds.

Meta-Cresol Affects Lipid Raft Organization in Membrane-Model Systems and Increases Membrane Leakage in Neural Cells

m-cresol is an excipient stabilizer used in numerous pharmaceutical formulations, including injectable insulin and vaccines. Therefore, we studied the effects of m-cresol in a range of concentrations from 10nM to 3mM on membrane model systems mimicking lipid-rafts and living neural-cells. First, the intrinsic fluorescence of m-cresol was studied. Both its fluorescence lifetime and anisotropy increased in the presence of liposomes, indicating a decreased mobility of the molecule. This interaction was dependent on membrane lipid composition. To elucidate this process, liposomes were labeled with several membrane probes spanning a range of in-depth locations and with preference for distinct lipid domains. For the probes located in the bilayer core (DPH and trans-parinaric acid), no effect was detected even for an m-cresol concentration of 300M, whereas for the more superficial NBD-DOPE and NBD-DPPE, >30M m-cresol induced a significant fluorescence lifetime decrease. Atomic force microscopy experiments were performed on ternary supported lipid bilayers containing raft-like liquid ordered domains (Lo). Indeed, it was observed that upon addition of m-cresol in the M range, a reduction of the Lo occurs without changing their thickness. For higher m-cresol concentrations, raft-like domains are not detected at all. Whole-cell voltage-clamp recordings from pyramidal-neurons isolated from the CA1 region of rat hippocampus (p21-p29) and from N1E-115 neuroblastoma cells were also performed. m-Cresol was applied during constant superfusion and the following parameters were monitored: series-resistance, whole-cell capacitance, holding-current (Vm=-70 mV), and another read-out for the leak-current. Results show that only the leak current was altered by m-cresol (>100 M). As a whole, we show that m-cresol interacts with the membrane, affecting lipid raft organization, with functional implications on neural-cell integrity. We thank F.C.T. Portugal for financial support (Ciência2007, SFRH/BD/64442/2009, PEst-OE/QUI/UI0612/2011).

The application of crystal soaking technique to study the effect of zinc and cresol on insulinotropin crystals grown from a saline solution.

The purpose of this study is to investigate the effect of zinc and cresol on the structure of insulinotropin crystals. Insulinotropin crystals grown from a saline solution were treated with zinc and/or m-cresol using a crystal soaking technique. The effects of these additives on the crystal structure were investigated with powder X-ray diffraction, photomicrography, and differential scanning calorimetry. The molecular interaction between insulinotropin and m-trifluorocresol in solution was also studied by 19F NMR: The data suggest that the original crystals grown from a saline solution have relatively weak lattice forces. After the addition of m-cresol to the suspension of the insulinotropin crystals, the crystals were immediately rendered amorphous. The m-cresol molecules which diffused into the crystals through solvent channels may have disturbed the lattice interactions that maintain the integrity of the crystal. In contrast, the zinc added to the suspension stabilized the crystal lattice so that the subsequent addition of m-cresol did not alter the integrity of the crystals. A marked increase in melting point (206 degrees versus 184 degrees) and heat of fusion (24.6 J/g versus 1.4 J/g) of the crystals was observed after the treatment with zinc. The solubility of the zinc treated crystals in a pH 7.1 phosphate buffered saline was 1/20 of that of the original crystals. When the insulinotropin crystals were treated with the additives using a crystal soaking method, the crystals underwent structural changes. Zinc stabilized the crystal lattice, and reduced the solubility of the peptide.

Determination of Microbial Activity in Marine Sediments by Resazurin Reduction

Abstract A simple method is presented to evaluate microbial activity in aquatic sediments. The method is based on resazurin reduction by microbial electron transport chains and reduced chemical compounds present in the sample. The addition of m-cresol, which inhibits enzyme activity, allows one to measure microbial metabolism by difference. Small aliquots of sediment (about 1 g FW) are incubated at 20°C with resazurin solution, with and without m-cresol. The sample is then filtered and the unreduced resazurin is measured at 600 nm. Testing the method with a bacterial suspension gave a resazurin reduction of 89 μg/h/109 cells. In a few marine coastal sediment samples, the resazurin reduction in aerobic conditions was in the range of 0.31 to 219.3 μg/h/g DW, which is equivalent to an oxygen consumption of 0.02 to 15.32 μg/h/g DW.

Heterogeneous-catalysis transformation of phenols

1. An investigation was made of the alkylation of m-cresol with butadiene in presence of zinc chloride deposited on alumina and of the cationite KU-1. 2. Alkylation led to the formation of 4- and 6-(2-butenyl)-m-cresols, of which the latter was cyclized to 2-ethyl-2,3-dihydro-6-methylbenzofuran and 2,7-dimethylchroman, the totalyield of which attained 50–60% 3. The addition of m-cresol to butadiene occurs in the 1,4-position.