José L. Martínez Hernández

Water quality monitoring using an enhanced chemiluminescent assay based on peroxidase-catalyzed peroxidation of luminol

Enhanced chemiluminescence (ECL) describes the phenomenon of the light output increase in the reaction of oxidation of luminol catalyzed by horseradish peroxidase (HRP) in the presence of certain phenolic compounds. This work summarizes the effects of preincubation of certain substances with HRP on the chemiluminescent reaction intensity. Preincubation of herbicide, detergent, surfactants (Brij-96 and Tween-20), phenol, metal ions (mercury, cobalt, and nickel), and bactericide with HRP had an inhibitory effect on the enzyme activity. HRP-preincubation with metal ions (cadmium, magnesium, and zinc), as well as with some insecticides, stimulated the chemiluminescent intensity. Calibration graphs were obtained to demonstrate the possibility to determine the pollutant concentration. Light emission from the peroxidase catalyzed enhanced chemilum inescence is affected by a wide number of chemicals and, therefore, the method can beused for on-site monitoring of water quality. A rapid and simple assay to detect water contamination has been developed.

Process alternatives for bioethanol production from mango stem bark residues

Three alternatives for bioethanol production from pretreated mango stem bark after maceration (MSBAM) were evaluated as a biorefinery component for the mango agroindustry. These included separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), and pre-saccharification followed by simultaneous saccharification and fermentation (PSSF). The effects on ethanol concentration, yield and productivity of pretreated MSBAM solids loading, Tween 20 addition, and temperature were used for process comparisons. The highest yields for the SHF, SSF, and PSSF process alternatives were 58.8, 81.6, and 84.5%, respectively. Since saccharification and fermentation are carried out in the same vessel in the SSF alternative, and no significant SSF and PSSF differences in ethanol concentration were observed, SSF is recommended as the best process configuration.

Determination of arachidonic acid based on the prostaglandin H synthase catalyzed reaction

This article presents a novel method of arachidonic acid (AA) determination based on the reaction catalyzed by prostaglandin H synthase (PGHs). The deoxygenated and nondeoxygenated (as control) buffers were used to obtain the PGHs preparations from bovine vesicular glands by two different methods. The higher specific activity was observed for solubilized preparations obtained by ultracentrifugation and deoxygenated buffers. The preparations obtained by Ca2+ treatment demonstrated higher stability of PGHs during its storage at −15°C. To record the initial rate of AA transformation, a spectrophotometric assay of PGHs cyclo-oxygenase and peroxidase activities was developed using adrenaline and ABTS as electron donors. No oxidation of A BTS was observed in the reaction of AA transformation catalyzed by the PGHs from bovinevesicular glands. However, this electron donor was successfully used in the reaction catalyzed by PGHs from sheep vesicular glands. No chemilum inescence was recorded in the reaction of AA transformation catalyzed by PGHs from bovine vesicular glands in the presence of luminol. The chemiluminescent intensity was measured after addition of hydrogen peroxide allowing quantitative assay of AA to be performed.