Isolation and partial characterization of three isoamylases of Rhyzopertha dominica F. (Coleoptera: Bostrichidae).

Three isoamylases of Rhyzopertha dominica (termed RdA70, RdA79, and RdA90 according to their relative mobility in gel electrophoresis) were isolated by ammonium sulfate fractionation and hydrophobic interaction chromatography. RdA70 and RdA79 showed an optimal pH of 7.0, whereas for RdA90 the optimal pH was 6.5. The three isoamylases remained stable at 50 degrees C for 1 h, but at 60 degrees C, all lost 50% of their activity in 20 min and were completely inactivated in 1 h. RdA70 and RdA79 were inhibited by albumin extracts from wheat samples varying widely in amylase inhibitory activity; however, RdA90 was highly resistant to inhibition. beta-Mercaptoethanol up to 30 mM increased the activity of the three isoamylases by 2.5-fold. The action pattern of the three isoamylases was typical of endoamylases; however, differences were observed on the hydrolytic efficiency rates measured as V(max)/K(m) ratio on starch, amylopectin, and amylose. The hydrolyzing action of RdA90 on starch and amylopectin (V(max)/K(m)=90.4+/-2.3 and 78.9+/-6.6, respectively) was less efficient than that on amylose (V(max)/K(m)=214+/-23.2). RdA79 efficiently hydrolyzed both amylopectin and amylose (V(max)/K(m)=260.6+/-12.9 and 326.5+/-9.4, respectively). RdA70 hydrolyzed starch and amylose at similar rates (V(max)/K(m)=202.9+/-5.5 and 215.9+/-6.2, respectively), but amylopectin was a poor substrate (V(max)/K(m)=124.2+/-7.4). The overall results suggest that RdA70 and RdA79 appear to belong to a group of saccharifying isoamylases that breaks down long fragments of oligosaccharide chains produced by the hydrolytic action of RdA90. The simultaneous action of the three isoamylases on starch, aside from the high resistance of RdA90 to wheat amylase inhibitors, might allow R. dominica to feed and reproduce successfully on the wheat kernel.

HALOBACTERIAS PROMOTORAS DE CRECIMIENTO VEGETAL ASOCIADAS A Lippia palmer! (VERBENACEAE) EN LA ZONA ÁRIDA DEL NOROESTE DE MÉXICO / Plant growth promoting halobacteria associated to plant growth promoting halobacteria associated to Lippia palmeri (Verbenaceae) in the arid zone of northwestern Mexico

RESUMEN La producción de orégano es de relevancia económica en el noroeste de México. Sin embargo, los productores para obtener altos rendimientos recurren a la fertilización química, pero su mal uso, agudiza la salinidad. Lippia palmeri crece de manera natural en suelos áridos, pobres en materia orgánica, alta salinidad y temperatura en el noroeste de México. En el contexto de una agricultura sustentable, los microorganismos mantienen la fertilidad del suelo e incrementan la productividad de la planta. Actualmente existe interés en proponer biofertilizantes en la agricultura de alta intrusión salina y elevadas temperaturas para el cultivo de orégano. Las Halobacterias Promotoras del Crecimiento de Plantas (HPCP), se han destacado por beneficiar a los cultivos nutrimentalmente y mitigar el efecto de la salinidad. El objetivo del presente trabajo consistió en identificar termo- y halo-tolerantes HPCP asociadas a la rizosfera de L. palmeri; se evaluó la actividad solubilizadora de fosfatos, producción de ácidos orgánicos, sideróforos y fijación de nitrógeno; se identificaron mediante el gen ARNr-16S aquellas con alta actividad evaluándose su efecto en la germinación y longitud radicular. Quince diferentes colonias sobresalieron al crecer en NaCl (0.25, 0.50 y 0.75 M) a 35 y 45 °C, destacando tres bacterias identificadas: Bacillus amyloliquefaciens, Bacillus subtilis y Bacillus licheniformis. El efecto en la longitud radicular es significativo por la aplicación de B. amyloliquefaciens. Estudios relacionados con la promoción vegetal deben ser considerados en posteriores estudios. Este es el primer informe de B. amyloliquefaciens como una bacteria fijadora de nitrógeno asociada a L. palmeri.

ABSTRACT The production of oregano is of economic relevance in northwestern Mexico. However, to obtain high yields, producers resort to chemical fertilization, but its misuse increases salinity. Lippia palmeri Watts is a species of oregano that naturally grows in arid soils with poor organic matter, high salinity and temperature in the northwestern Mexico. In the context of sustainable agriculture, microorganisms activate soil fertility and increase plant productivity. Currently there is interest in proposing biofertilizers in the agriculture with high saline intrusion and temperatures for the cultivation of oregano. The Plant Growth Promoting Halobacteria (HPCP) have stood out by the beneficiary of the nutritious crops and mitigate the effect of the salinity. The goal of this work was to identify HPCP associated to the rhizosphere of L. palmeri, thermo and halotolerant; phosphate solubilizing activity, organic acid production, siderophores and nitrogen fixation were evaluated; the highest activity colonies were identified by the rRNA-16S gene and the effect on germination and root length was evaluated. Fifteen different colonies stood out when growing in NaCl (G.25, G.5G and G.75 M) at 35 and 45 °C, from which three bacteria were identified: Bacillus amyloliquefaciens, Bacillus subtilis and Bacillus licheniformis. The effect on root length was significant for B. amyloliquefaciens. Studies related to plant promotion should be involved in subsequent studies. This is the first report of Bacillus amyloliquefaciens as a nitrogen fixing bacteria associated with Lipia palmeri.

Anti-Inflammatory Activity and Changes in Antioxidant Properties of Leaf and Stem Extracts from Vitex mollis Kunth during In Vitro Digestion.

Vitex mollis is used in traditional Mexican medicine for the treatment of some ailments. However, there are no studies on what happens to the anti-inflammatory activity or antioxidant properties and total phenolic content of leaves and stem extracts of Vitex mollis during the digestion process; hence, this is the aim of this work. Methanolic, acetonic, and hexanic extracts were obtained from both parts of the plant. Extract yields and anti-inflammatory activity (elastase inhibition) were measured. Additionally, changes in antioxidant activity (DPPH and ABTS) and total phenols content of plant extracts before and after in vitro digestion were determined. The highest elastase inhibition to prevent inflammation was presented by hexanic extracts (leaf = 94.63% and stem = 98.30%). On the other hand, the major extract yield (16.14%), antioxidant properties (ABTS = 98.51% and DPPH = 94.47% of inhibition), and total phenols (33.70 mg GAE/g of dried sample) were showed by leaf methanolic extract. Finally, leaf and stem methanolic extracts presented an antioxidant activity increase of 35.25% and 27.22%, respectively, in comparison to their initial values after in vitro digestion process. All samples showed a decrease in total phenols at the end of the digestion. These results could be the basis to search for new therapeutic agents from Vitex mollis.