Publications by authors named "Ramirez-Lepe M"

Pochonia chlamydosporia has been intensively studied in nematode control of different crops. We have investigated the interaction between P. chlamydosporia and the model system Arabidopsis thaliana under laboratory conditions in the absence of nematodes.

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The effect of chitosan on growth of Trichoderma spp., a cosmopolitan genus widely exploited for their biocontrol properties was evaluated. Based on genotypic (ITS of 18S rDNA) characters, four isolates of Trichoderma were identified as T.

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The antimicrobial activity of 12 plant extracts was tested against the phytopathogens Alternaria alternata and Fusarium solani. In addition, the compatibility of the extracts toward Bacillus liqueniformis, a biofertilizer and a non-target microorganism, was assessed. Plants tested belong to the Euphorbiaceae, Asteraceae, Crassulaceae, Rubiaceae, Convolvulaceae, Verbenaceae, Orchidaceae, Nyctaginaceae, Boraginaceae, and Tiliaceae families and were collected in the State of Oaxaca.

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The insecticidal activity after field exposure of an aluminum-carboxymethylcellulose microencapsulated formulation of Bacillus thuringiensis israelensis (Bti) spore-toxin complex, with malachite green as photoprotective agent, was evaluated using third-instar Aedes aegypti (L.) larvae in laboratory bioassays in Veracruz, México. Four insecticide treatments and an untreated control were compared at low and high doses over 96 d of field exposure under full sun or full shade conditions: 1) microencapsulated Bti spore-toxin complex, 2) nonmicroencapsulated Bti spore-toxin complex, 3) a commercial Bti formulation, 4) a commercial formulation of temephos, and 5) an untreated control.

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Enantiomerically pure alpha-hydroxy amides have been prepared from the corresponding alpha-oxo esters by the use of a double sequence reaction involving in a first step the highly enantioselective Saccharomyces cerevisiae bioreduction and then in a second step, the resulting alpha-hydroxy esters followed a non-enantiospecific lipase catalyzed aminolysis with n-butylamine reaction. In the first non-organic solvent process, the moistened baker's yeast reduced seven alpha-oxo esters with high conversions degree (93% for one substrate and >99% for the others) and high enantioselectivities [>99% for all the substrates except for ketopantoyl lactone, which gave 88% of enantiomeric excess (ee)]. At the same way, the isolated resulting chiral alpha-hydroxy esters were subjected to the second Candida antarctica lipase fraction B (CAL-B) catalyzed aminolysis in dioxane conducting to the corresponding chiral alpha-hydroxy amides with high conversions degree, between 88 and 99%.

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A chitinolytic enzyme from Bacillus thuringiensis subsp. aizawai has been purified and its molecular mass was estimated ca. 66 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

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Article Synopsis
  • The research explored the spray-drying of Bacillus thuringiensis subsp. israelensis (Bti) spore-toxin complex using different materials like maltodextrin, corn starch, and nixtamalized corn flour to enhance its larvicidal effectiveness against Aedes aegypti larvae.
  • The results indicated that the use of nixtamalized corn flour provided significantly higher toxicity levels (up to 81% increased effectiveness) compared to unformulated products, suggesting its potential as an effective delivery medium.
  • Dried products also showed a low water activity, indicating they could be stored for longer periods without microbial growth, which is beneficial for maintaining the potency of the insecticidal agent.
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The complete cry11A region gene of Bacillus thuringiensis ssp. israelensis was fused in frame to the 3' end of the GST gene under the control of the Saccharomyces cerevisiae HXK1 promoter. The fusion protein GST-cry11A was expressed in S.

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