Biomedical subjects

P Melgarejo

Publications and source records attributed to P Melgarejo.

7 recordsLinked to original sources

PubMed2006

Effect of stabilizers on the shelf-life of Penicillium frequentans conidia and their efficacy as a biological agent against peach brown rot.

Stabilizers were added to conidia of Penicillium frequentans at two different points of the production-formulation process to improve shelf-life of conidia stored at different temperatures. Effects were also tested on conidial germination and production. Germination of conidia without additives was 90.2%; sodium chloride, potassium chloride, triton TX100, dimethyl sulphoxide, peroxidase, 0.375% and 0.075% ascorbic acid, 7.5% and 3.75% sucrose, and 7.5% and 3.75% d-sorbitol reduced significantly (P=0.05) conidial germination, while no effect was observed with glucose, lactose, maltose, sodium glutamate, glycerol, peptone, sodium alginate, carboximethylcellulose, Tween 80, and gelatine. Production of P. frequentans conidia in solid-state fermentation without additives was 1.07 conidia x 10(8) g(-1) of dry substrate. The highest tested doses of glucose, lactose, maltose, sodium glutamate, and glycerol enhanced production of P. frequentans, while the lowest tested doses of d-sorbitol and ascorbic acid reduced it. No significant effect was observed with sucrose, peptone, sodium alginate, carboximethylcellulose, gelatine and Tween 80. Conidial germinability after one year of storage at different temperatures was studied in some formulations. It was lower than 18% after 365 days of storage at room temperature in control samples (without any additive), being enhanced when 7.5% glucose, 7.5% glycerol, or 1.5% sodium alginate was added to the substrate in bags before fermentation; or when 7.5% glucose, 7.5% sodium glutamate, or 1.5% sodium alginate was added to conidia before drying. Germinability of conidia produced without any additive and stored at 4 degrees C was significantly higher (38%) than at room temperature, being enhanced when 7.5% glycerol or 1.5% sodium alginate was added to the substrate in bags before fermentation; and when 7.5% glucose, or 1.5% sodium alginate was added to conidia before drying. No effect was observed with the presence or absence of light or high vacuum. Four formulations of P. frequentans conidia reduced disease incidence by more than 55%. The relationship of the disease control with the viability of P. frequentans was discussed.

Biological Factors↗

PubMed2004

Solid substrate production of Epicoccum nigrum conidia for biological control of brown rot on stone fruits.

Production of conidia of Epicoccum nigrum, a biocontrol agent of the fungal pathogen Monilinia laxa, was tested in liquid- and solid-state fermentation. Liquid fermentation was conducted in 250 ml Erlenmeyer flasks containing 50 ml of a mineral medium (containing per litre: 20 g lactose, 10 g NO3K, 1 g K2HPO4, 0.5 g MgSO4.7H2O, and 1 ml of a minor-element solution), inoculated with 2 x 10(5) E. nigrum conidia ml(-1), and incubated at 20-25 degrees C and 150 rpm for 7 days. Solid-state fermentation was carried out in specially designed plastic bags (600 cm3) (VALMIC) containing either 50 g of peat/vermiculite (1:1, w/w), or 50 g of peat/vermiculite/lentil meal (1:1:1, w/w/w) with 40% (v/w) initial moisture content. Substrate was inoculated with a conidial suspension of E. nigrum to give 10(5) conidia g(-1) substrate, and bags were incubated at 20-25 degrees C for 7 days in darkness. The amount of conidia of E. nigrum obtained in solid-state fermentation with substrate based on peat/vermiculite/lentil meal was 10-fold higher than with substrate based on peat/vermiculite or in liquid fermentation. Conidial production under these conditions was maintained in the range of 10(8) conidia g(-1) substrate from 10 to 150 days after inoculation. Germinability of these conidia was >90%. Addition of other nutrients than lentil meal to peat/vermiculite did not enhance production of conidia. Presence of peat in the substrate was necessary for good conidia production, but change in the kind of peat or vermiculite did not improve conidial production. Conidial production was similar when the substrate was inoculated with 10(5), 10(6) or 10(7) conidia g(-1) dry substrate. Incubation of bags in light conditions did not enhance conidial production. Fresh conidia produced in this solid-state fermentation system reduced the incidence and lesion diameter induced by M. laxa on peaches.

Ascomycota↗

PubMed2003

Drying of Epicoccum nigrum conidia for obtaining a shelf-stable biological product against brown rot disease.

AIMS: The effects of freeze-drying, spray-drying and fluidized bed-drying on survival of Epicoccum nigrum conidia were compared. METHODS AND RESULTS: Viability of E. nigrum conidia (estimated by measuring its germination) was 100% after fluidized bed-drying and freeze-drying, but it was determined that skimmed milk must be added in the case of freeze-drying conidia. Addition of other protectants (Tween-20, peptone, sucrose, glucose, starch and peptone + starch) to skimmed milk before freeze-drying did not improve the conidial viability which was obtained with skimmed milk alone. Glycerol had a negative effect on the lyophilization of E. nigrum conidia. Epicoccum nigrum conidia freeze-dried with skimmed milk, or fluidized bed-dried alone maintained an initial viability for 30 and 90 days, respectively, for storage at room temperature. Epicoccum nigrum conidial viability after spray-drying was lower than 10%. CONCLUSIONS: The best method to dry E. nigrum conidia was fluidized bed-drying. Conidia without protectants dried by this method had 100% viability and survived for 90 days at room temperature. SIGNIFICANCE AND IMPACT OF STUDY: This paper deals with methods for the potential formulation of a biocontrol agent which is being tested for eventual commercialization.

Ascomycota↗

PubMed2000

Surface hydrophobicity, viability and efficacy in biological control of Penicillium oxalicum spores produced in aerial and submerged culture.

The surface hydrophobicity, viability and biocontrol ability of Penicillium oxalicum spores, produced either in aerial or submerged culture, were characterized. A phase distribution test showed that spores produced in both methods of culture were highly hydrophobic, but those produced in aerial culture were more hydrophobic. Spores stored fresh at either 4 or 25 degrees C retained a high viability (80%) after 27 weeks of storage, although aerial spores survived better. Freeze-drying severely affected viability, especially of submerged spores. Biocontrol ability against Fusarium oxysporum f. sp. lycopersici was studied in the growth chamber. Aerially- produced spores were more effective than submerged ones. Aerially-produced P. oxalicum spores appeared to have more advantages than those produced by submerged culture, in relation to both viability and efficacy. These results demonstrate that physiological changes occur depending on production conditions which significantly influences quality of the biocontrol agent.

Air↗

PubMed1997

Ecophysiological factors affecting growth, sporulation and survival of the biocontrol agent Penicillium oxalicum.

The effect of temperature, pH, water potential and sources of nitrogen and carbon on the biocontrol agent Penicillium oxalicum were studied in vitro. The fungus is xerotolerant, mesophillic and has a wide pH tolerance. The parameters evaluated (germination, germ tube length, growth rate and sporulation) showed different sensitivities to the environmental factors. Peptone and free amino acids gave the highest growth rates and high levels of sporulation. Xylose, mannose and fructose gave the highest growth rates and mannose induced strong sporulation. The effect of nutrients (mannose + arginine) and water potential was also studied in vivo. The xerotolerant character of the fungus was confirmed. From this study we consider Penicillium oxalicum ecologically competent to perform effectively as a biocontrol agent in the soil environment.

Journal Article↗

PubMedDate not supplied

[Inverted papillomas of the nasal sinuses].

After reviewing the Arnau de Vilanova Hospital's records, a total of ten cases of inverted papillomas were found. Nasal obstruction was present in 100% of the cases. External surgery was performed in 70% of these patients, finding that in 50% of them, the real size of the tumor was smaller than that show in the radiological study. After surgical treatment, only one of the patients developed a malignant tumor. Incidence of papilloma recurrence was 30%.

Adult↗

PubMedDate not supplied

[Peritonsillar abscess: treatment guidelines].

A prospective study was carried out on 25 patients showing symptoms suggestive of peritonsillar abscess. Twelve patients were treated with i.v. antibiotics and three months later underwent tonsillectomy. Thirteen patients underwent acute tonsillectomy within 24-48 hours. In order to evaluate the benefits of acute tonsillectomy we compared three parameters; operation length, intraoperative bleeding and overall length of hospitalization.

Abscess↗