Neochloris oleoabundans cell wall rupture through melittin peptide: a new approach to increase lipid recovery.

OBJECTIVES: Microalgae cell wall affects the recovery of lipids, representing one of the main difficulties in the development of biofuel production. This work aimed to test a new method based on melittin peptide to induce a cellular disruption in N. oleoabundans. RESULTS: Neochloris oleoabundans cells were grown at 32 °C in the presence of a high concentration of nitrate-phosphate, causing a cell disruption extent of 83.6%. Further, a two-fold increase in lipid recovery following melittin treatment and solvent extraction was observed. Additionally, it was possible to verify the effects of melittin, both before and after treatment on the morphology of the cells. Scanning electron microscopy (SEM) and confocal images of the melittin-treated microalgae revealed extensive cell damage with degradation of the cell wall and release of intracellular material. CONCLUSIONS: Melittin produced a selective cell wall rupture effect in N. oleoabundans under some culture conditions. These results represent the first report on the effect of melittin on lipid recovery from microalgae.

Systematic bioprospection for cellulolytic actinomycetes in the Chihuahuan Desert: isolation and enzymatic profiling.

The quest for microbial cellulases has intensified as a response to global challenges in biofuel production. The efficient deconstruction of lignocellulosic biomass holds promise for generating valuable products in various industries such as food, textile, and detergents. This article presents a systematic bioprospection aimed at isolating actinomycetes with exceptional cellulose deconstruction capabilities. Our methodology explored the biodiverse oligotrophic region of Cuatro Cienegas, Coahuila, within the Chihuahuan Desert. Among the evaluated actinomycetes collection, 78% exhibited cellulolytic activity. Through a meticulous screening process based on enzymatic index evaluation, we identified a highly cellulolytic Streptomyces strain for further investigation. Submerged fermentation of this strain revealed an endoglucanase enzymatic activity of 149 U/mg. Genomic analysis of strain Streptomyces sp. STCH565-A revealed unique configurations of carbohydrate-active enzyme (CAZyme) genes, underscoring its potential for lignocellulosic bioconversion applications. These findings not only highlight the significance of the Chihuahuan Desert as a rich source of cellulolytic microorganisms but also offer insights into the systematic exploration and selection of high-performing cellulolytic microorganisms for application in diverse environmental contexts. In conclusion, our bioprospecting study lays a foundation for harnessing the cellulolytic potential of actinomycetes from the Chihuahuan Desert, with implications for advancing cellulose deconstruction processes in various industries. The findings can serve as a blueprint for future bioprospecting efforts in different regions, facilitating the targeted discovery of microorganisms with exceptional cellulosic deconstruction capabilities.

Persistence of Toxic Activity of Fermentation Extracts from Bacillus thuringiensis var. israelensis after More Than Three Decades of Storage.

This study was carried out to determine the persistence of toxicity of fermentation extracts of Bacillus thuringiensis var. israelensis after more than three decades of storage. For this purpose, a population of Aedes aegypti was established. The mortality rate of 20 spore-crystal extracts purified using the acetone-lactose coprecipitation method was measured and evaluated by bioassays according to a modified WHO protocol. The extracts with the highest mortality rate were determined in triplicate by their LD50 and LD98. All extracts showed toxicity at the highest tested dose (1000 ppm) and some, such as strains 3260 and 3501, still killed larvae at doses as low as 0.01 ppm. These data are surprising because no study on the activity of B. thuringiensis toxic proteins after such a long storage time has been reported.

Genome annotation of a Saccharomyces sp. lager brewer's yeast.

The genome of lager brewer's yeast is a hybrid, with Saccharomyces eubayanus and Saccharomyces cerevisiae as sub-genomes. Due to their specific use in the beer industry, relatively little information is available. The genome of brewing yeast was sequenced and annotated in this study. We obtained a genome size of 22.7 Mbp that consisted of 133 scaffolds, with 65 scaffolds larger than 10 kbp. With respect to the annotation, 9939 genes were obtained, and when they were submitted to a local alignment, we found that 53.93% of these genes corresponded to S. cerevisiae, while another 42.86% originated from S. eubayanus. Our results confirm that our strain is a hybrid of at least two different genomes.

Effects of culture medium and formulation on the larvicidal activity of the mosquito pathogen Lagenidium giganteum (Oomycetes: Lagenidiales) against Aedes aegypti.

In this work, we examined the production of infective zoospores of Lagenidium giganteum in four culture media, and the larvicidal activity of the cultures was determined against Aedes aegypti larvae, as well as the effect of polymer encapsulation. Medium containing sunflower seed extract showed the greatest production of zoospores, 5.92×10(6) zoospores/ml after six days of fermentation at 25±2°C and 150rpm shaking. This culture tested against A. aegypti 1st stage larvae caused different mortality rates at 24, 48 and 72h posttreatment. The LC(50) obtained was 43.9, 41.1 and 42.9µl of total culture/ml, at 24, 48 and 72h posttreatment respectively, while the culture grown in medium with soybean meal showed 3-5 times higher LC(50) values. Finally, the total culture including mycelium, zoospores and presporangia formulated with 2.5% pectin showed significantly higher mortality rates, around 100% more than the unformulated culture, whose values were from 40 to 1% at 3, 6, 9, and 12d posttreatment in the bioassays carried out in the laboratory to determine residual activity.

Evaluation of polymer-based granular formulations of Bacillus thuringiensis israelensis against larval Aedes aegypti in the laboratory.

A strategy to increase residual activity of Bacillus thuringiensis serovar. israelensis (Bti) extract through slow-release formulations and protection from solar radiation was studied. The median lethal concentration (LC50) and 90% lethal concentration (LC90) levels of laboratory-reared early 4th-stage larval Aedes aegypti after exposure to Bti extract were determined. Formulations with 4 polymers and 1 solar protectant were prepared, and their shelf lives were evaluated for year-long storage at 20-35 degrees C and 50-80% relative humidity. Also, the effect of ultraviolet light on unformulated (extract) and formulated Bti larvicidal activity persistence was determined. Laboratory bioassays were conducted with larval Ae. aegypti introduced into treated and control containers at 1, 2, 7, 14, 21, 28, 35, and 42 days after treatment, and larval mortalities were checked 24 h after introduction. Probit analysis of Bti extract showed LC50 and LC90 values of 0.016 and 0.051 mg/liter, respectively. The polymer-based Bti formulations showed no significant loss of insecticidal activity after 8 months of storage. Ultraviolet irradiation reduced activity of unformulated Bti extract after different exposure times, up to 40-46%, whereas Bti formulated with gelatin or acacia gum showed lower variation in larvicidal activity than formulations with sodium alginate and paraffin for protecting the activity of Bti toxin. Residual activity against 4th-stage Ae. aegypti in the laboratory for the formulation containing acacia gum at 10% (w/w) was 80% mortality at 14 days after treatment, whereas the Bti formulation containing gelatin (10%, w/w) caused 65% mortality. In addition, Bti formulations made with paraffin at 5% (w/w) sustained up to 60% mortality for 21 days. Unformulated Bti showed only 2.6% mortality, and a commercial preparation maintained 37% mortality, both at 14 days after treatment.