Publications by authors named "Roque A Hours"

CHase catalyzes chlorogenic acid (CGA) hydrolysis to yield equimolar quinic (QA) and caffeic (CA) acids, products of high value and keen industrial interest. We proposed the preparation and characterization of the nonviable mycelium of Aspergillus niger AKU 3302 containing a cell-associated CHase (CHase biocatalyst) for application in hydrolyzing the CGA from yerba mate residues to produce QA and CA. When the vegetative mycelium was heated at 55 °C for 30 min, no loss of CHase activity occurred, but vegetative mycelial growth and spore germination ended.

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Article Synopsis
  • Histamine and other biogenic amines in fish cannot be removed through heating or chemical methods, necessitating alternative approaches for elimination.
  • A new method combines fungal amine oxidase (FAO) and bacterial aldehyde oxidase (ALOX) to effectively convert histamine into harmless byproducts, achieving a 100% yield of imidazole 4-acetic acid.
  • The presence of ALOX is crucial for the complete reaction, as its absence results in incomplete processing of detoxifying harmful amines.
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Due to the indigestibility, utilization of konjac taro, has been limited only to the Japanese traditional konjac food. preparation with konjac taro was examined to utilize konjac taro as a source of utilizable carbohydrates. AKU 3302 was selected as a favorable strain for preparation, while used extensively in brewing industry was not so effective.

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CHM 43 have D-mannitol dehydrogenase (quinoprotein glycerol dehydrogenase) and flavoprotein D-fructose dehydrogenase in the membranes. When the two enzymes are functional, D-mannitol is converted to 5-keto-D-fructose with 65% yield when cultivated on D-mannitol. 5-Keto-D-fructose production with almost 100% yield was realized with the resting cells.

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Membrane-bound sorbosone dehydrogenase (SNDH) of Gluconacetobacter liquefaciens oxidizes l-sorbosone to 2-keto-l-gulonic acid (2KGLA), a key intermediate in vitamin C production. We constructed recombinant Escherichia coli and Gluconobacter strains harboring plasmids carrying the sndh gene from Ga. liquefaciens strain RCTMR10 to identify the prosthetic group of SNDH.

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A novel oxidation of D-pentonates to 4-keto-D-pentonates was analyzed with Gluconobacter thailandicus NBRC 3258. D-Pentonate 4-dehydrogenase activity in the membrane fraction was readily inactivated by EDTA and it was reactivated by the addition of PQQ and Ca. D-Pentonate 4-dehydrogenase was purified to two different subunits, 80 and 14 kDa.

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Enzymatic decomposition of gelatin layers on used X-ray films and repeated utilization of the enzyme for potential application in silver recovery were investigated using keratinolytic serine proteases from Purpureocillium lilacinum LPS # 876. At pH 9.0, the enzymatic reaction was enhanced by the increase of enzyme concentration or by the increase of the temperature up to 60℃.

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Six nonpathogenic fungal strains isolated from alkaline soils of Buenos Aires Province, Argentina (Acremonium murorum, Aspergillus sidowii, Cladosporium cladosporoides, Neurospora tetrasperma, Purpureocillium lilacinum (formerly Paecilomyces lilacinus), and Westerdikella dispersa) were tested for their ability to produce keratinolytic enzymes. Strains were grown on feather meal agar as well as in solid-state and submerged cultures, using a basal mineral medium and "hair waste" as sole sources of carbon and nitrogen. All the tested fungi grew on feather meal agar, but only three of them were capable of hydrolyzing keratin, producing clear zones.

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Wickerhamomyces anomalus is pectinolytic yeast isolated from citrus fruits peels in the province of Misiones, Argentine. In the present work, enzymes produced by this yeast strain were characterized, and polygalacturonase physicochemical properties were determined in order to evaluate the application of the supernatant in the maceration of potato tissues. W.

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D-Ribose and 2-deoxy-D-ribose were oxidized to 4-keto-D-ribonate and 2-deoxy-4-keto-D-ribonate respectively by oxidative fermentation, and the chemical structures of the oxidation products were confirmed to be as expected. Both pentoses are important sugar components of nucleic acids. When examined, purine nucleosidase activity predominated in the membrane fraction of acetic acid bacteria.

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Paecilomyces lilacinus (Thom) Samson LPS 876, a locally isolated fungal strain, was grown on minimal mineral medium containing "hair waste," a residue from the hair-saving unhairing process, and produced a protease with keratinolytic activity. This enzyme was biochemically characterized. The optimum reaction conditions, determined with a response surface methodology, were 60°C and pH 6.

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4-Keto-D-arabonate (D-threo-pent-4-ulosonate) and 4-keto-D-ribonate (D-erythro-pent-4-ulosonate) were prepared from D-arabinose and D-ribose by two successive reactions of membrane-bound enzymes, D-aldopentose 4-dehydrogenase and 4-keto-D-aldopentose 1-dehydrogenase of Gluconobacter suboxydans IFO 12528. Alternatively, they were prepared from D-arabonate and D-ribonate with another membrane-bound enzyme, D-pentonate 4-dehydrogenase. Analytical data confirmed the chemical structures of the 4-pentulosonates prepared.

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In our previous study, a new microbial reaction yielding 4-keto-D-arabonate from 2,5-diketo-D-gluconate was identified with Gluconacetobacter liquefaciens RCTMR 10. It appeared that decarboxylation and dehydrogenation took place together in the reaction. To analyze the nature of the reaction, investigations were done with the membrane fraction of the organism, and 4-keto-D-arabinose was confirmed as the direct precursor of 4-keto-D-arabonate.

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Rhamnosidases are enzymes that catalyze the hydrolysis of terminal nonreducing L-rhamnose for the bioconversion of natural or synthetic rhamnosides. They are of great significance in the current biotechnological area, with applications in food and pharmaceutical industrial processes. In this study we isolated and characterized a novel alkaline rhamnosidase from Acrostalagmus luteo albus, an alkali-tolerant soil fungus from Argentina.

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Production of 4-keto-D-arabonate (4KAB) was confirmed in a culture medium of Gluconacetobacter liquefaciens strains, newly isolated from water kefir in Argentina. The strains rapidly oxidized D-glucose, D-gluconate (GA), and 2-keto-D-gluconate (2KGA), and accumulated 2,5-diketo-D-gluconate (25DKA) exclusively before reaching the stationary phase. 25DKA was in turn converted to 4KAB, and 4KAB remained stable in the culture medium.

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Plant-pathogenic fungi produce an array of extracellular hydrolytic enzymes that enable them to penetrate and infect the host tissue; these enzymes are collectively called cell wall-degrading enzymes (CWDE). They may contribute to pathogenesis by degrading wax, cuticle and cell walls, thus aiding tissue invasion and pathogen dissemination. Furthermore, they can act as elicitors of host defense reaction.

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