Efecto de la actividad de agua y la modificación de la atmósfera gaseosa sobre la producción y calidad de conidios de Beauveria bassiana
Biological control is defined as the reduction of pest populations using natural enemies, Beauveria bassiana is wildely distributed in nature, has a potential to control nearly of 70 pests of insects, this feature has increased the interest for industrial production, in fact in many places of the wo...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2009 |
| País: | México |
| Institución: | Universidad Autónoma Metropolitana |
| Repositorio: | Repositorio Institucional de la UAM Iztapalapa |
| Idioma: | español |
| OAI Identifier: | oai:bindani.izt.uam.mx:1544bp39d |
| Acceso en línea: | https://doi.org/10.24275/uami.1544bp39d |
| Access Level: | acceso abierto |
| Palabra clave: | info:eu-repo/classification/LEM/Hongos como agentes de control biológico info:eu-repo/classification/LEM/Cónidos info:eu-repo/classification/LEM/Fungi -- Biological control systems info:eu-repo/classification/LEM/Conid info:eu-repo/classification/LEM/Plagas de insectos info:eu-repo/classification/LEM/Plagas de insectos -- Biological control info:eu-repo/classification/cti/6 |
| Sumario: | Biological control is defined as the reduction of pest populations using natural enemies, Beauveria bassiana is wildely distributed in nature, has a potential to control nearly of 70 pests of insects, this feature has increased the interest for industrial production, in fact in many places of the world there are commercial formulations based on Beauveria bassina. Produces a different kind of conidia, depending on culture conditions. The method used for conidia production affects bioinsecticide activity of fungus, and the main production methods are solid state fermentation, which is defined as microorganism grown on moisted solid substrates with enough water to allow metabolisms, with no water leakeage and with air as continue phase. Other culture method is a biphasic system, in which inoculum is produced in liquid media, followed by a solid production medium, in both production systems the desirable product are conidia. Composition effect was evaluated using four media: Sabouraud Dextrose Agar 4 %, Potato Dextrose Agar, Defined medium and Colloid Chitin 1 % medium. The highers Vr were 79, 76, 79, 75 µm/h respectively, with aW = 1. The maximum conidia production (3.6x109 conidia/plate) was reached with Sabouraud Dextrose Agar 4 % at aW=0.994. Conidia production decreased as a function of aW, in fact differences of one magnitud order were observed between aW extremes. Maximum conidia density was 6.9 x 108 conidia/cm2 reached with colloidal chitin and aW = 0.973. The medium compotition effect was showed over Vr and conidia production, the best results were obtained with complex media. In solid state fermentation maximal yield was 1.15 x 1010 conidia/gdss, this value was obtained with a moisture content of 66 % (aW = 1), however, yield reduced as moisture content increased. In addition, the use of substrates mixes (wheat bran and sugar cane baggase) higher yields were obtained with media containing only wheat bram, in fact the presence of sugar cane as a texturizer reduced in conidial yields, however real yields (conidia per gram of wheat bran) did not show any stadistical difference in all mixtures. When differents levels of inocula (1x106 , 7x106 , 5x107 conidia/gdss) were tested, similar yields were observed (1 x 1010 conidia/gdss), but time at which this yield was reached (t10) was reduced as inoculum increases; t10 was proposed as fermentations quality parameter. Viability values in at times with the highest yield (1 x 1010 conidia/gdss) were 77.5, 61 and 54% for inocula of 1x106 , 7x106 , 5x107 conidia/dss, respectively. A inoculum size of 1x106 conidia/dss was selected for further experiments. Gaseous atmosphere was modified after 72 h once mycelia was visible, in oxygen riched atmosphere O2/CO2 (26/0 %) yield of 1x1010 conidia/gdss was obtained, this yield was similar to that reached in normal atmosphere O2/CO2 (21/0 %). Nonetheless, using atmospheres with O2/CO2 ratios of 21/5 % and 16/5 %, yields were substantially reduced: 1.4x109 and 5.8x108 conidia/gdss, respectively. CO2 mixtures showed mycelia disruption at the end of cultures, this was more evident in a atmosphere of O2/CO2 : 16/5 %. Conidial viability was affected when atmosphere was modified, values were 73, 58, 44 and 39 % in O2/CO2 (%) mixtures of 21/0, 26/0, 21/5 and 16/5, respectively. Finally, bioassays were performed using Tenebrio molitor larvae. Maximum mortality (52%) was reached with conidia obtained in a normal atmosphere (O2/CO2,: 21/0) with a 50 lethal time (TL50) of 16.9 d. Atmosphere modification caused a negative effect on Beauveria bassiana virulence, since mortality was equal or less to 20 % in the rest of treatments, Viability and hidrofobicity showed as well a reduction with atmosphere modification. The main conclusions were: 1. Beauveria bassiana is very sensitive to culture media composition and water activity. Better radial extension rates, conidia yields and growth were obtained with complex nitrogen sources and water activity values closer to 1. 2. As a recommendation for production systems, the highest solid state fermentation conidia yields (1 x 1010 cnidias/gdss) were reached with normal atmosphere, wheat bran as a substrate, moisture contents of 66 % (aW = 1), a inoculum zise of 1 x 106 conidia/gdss, with an inoculum age of 10 days. Sugar cane bagaze as texturizer did not show effect over conidia yields. 3. Accumulation of CO2 in culture of Beauveria bassiana should be regarded as a detrimental factor. In this work the presence of CO2 in gaseous atmosphere was a negative effect on fungal growth, yields and conidia viability. A clear relationship between conidia relative hydrofobicity and virulence was no found. |
|---|