Licia M. Pera

Fall Armyworm Strains (Lepidoptera: Noctuidae) in Argentina, Their Associate Host Plants and Response to Different Mortality Factors in Laboratory

Abstract The aim of this research was to identify the existence of different Spodoptera frugiperda (J.E. Smith) (FAW) host strains in Argentina, and to determine their behaviors in the presence of different mortality factors. Populations belonging to these strains were tested with the pesticides chlorpyriphos and cypermethrin, transgenic corn germplasms expressing Cry proteins 1Ab or 1F, and an indigenous Bacillus thuringiensis strain. The relation of these strains with the host plant species and crop utilization, subsistence or commercial ones, is discussed. The response to the assayed insecticides, Bt transgenic corn and Bt suspension was diverse, showing wide variability in mortality rates. This research validates the need of intensive studies relating resistance phenomena with the differential behavior of the host strains inhabiting Argentina. Host plant and crop utility is not a determinant for the identity of the colonizing strain, so molecular identification of the strains is highly recommended before study of any aspect of the FAW in Argentina.

Effect of environmental conditions on extracellular lipases production and fungal morphology from Aspergillus niger MYA 135

Under the current assay conditions, lipase production in mineral medium was only detected in the presence of vegetable oils, reaching the highest specific activity with olive oil. In this way, effect of different environmental conditions on fungal morphology and olive oil‐induced extracellular lipases production from Aspergillus niger MYA 135 was studied. It was observed that addition of 1.0 g l–1 FeCl3to the medium encouraged filamentous growth and increased the specific activity 6.6 fold after 4 days of incubation compared to the control. However, major novelty of this study was the satisfactory production of an acidic lipase at initial pH 3 of the culture medium (1.74 ± 0.06 mU μg–1), since its potencial applications in food and pharmaceutical industry are highly promising. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Mycelium-bound lipase production from Aspergillus niger MYA 135, and its potential applications for the transesterification of ethanol

The potential biotecnological applications of both constitutive and inducible lipase sources from Aspergillus niger MYA 135 were evaluated. To this end, the effect of environmental conditions on mycelium‐bound lipase production from this strain was studied, when cultured either in the absence or presence of 2% olive oil. It was previously reported that mycelium‐bound lipase from Aspergillus niger MYA 135 possess high stability in reaction mixtures containing ethanol; which could be especially important for their use in biodiesel synthesis. In this connection, the performance of the lipase sources produced in the transesterification of ethanol using p‐nitrophenyl palmitate as acyl donor was also explored.

Characterization of native Bacillus thuringiensis strains and selection of an isolate active against Spodoptera frugiperda and Peridroma saucia.

Twelve Bacillus thuringiensis (Bt) strains, isolated from larvae and soil samples in Argentina, were molecularly and phenotypically characterized and their insecticidal activities against Spodoptera frugiperda and Peridroma saucia were determined. One isolate—Bt RT—produced more than 93% mortality on first instar larvae of both species, which was higher than that produced by the reference strain Bt 4D1. Bt RT carried a different cry gene profile than Bt 4D1. Scanning electron microscopy showed the presence of bipyramidal and cuboidal crystals. Phenotypic characterization revealed lytic enzymes that could contribute to Bt pathogenicity.

Tailoring fungal morphology of Aspergillus niger MYA 135 by altering the hyphal morphology and the conidia adhesion capacity: biotechnological applications

Current problems of filamentous fungi fermentations and their further successful developments as microbial cell factories are dependent on control fungal morphology. In this connection, this work explored new experimental procedures in order to quantitatively check the potential of some culture conditions to induce a determined fungal morphology by altering both hyphal morphology and conidia adhesion capacity. The capacity of environmental conditions to modify hyphal morphology was evaluated by examining the influence of some culture conditions on the cell wall lytic potential of Aspergillus niger MYA 135. The relative value of the cell wall lytic potential was determined by measuring a cell wall lytic enzyme activity such as the mycelium-bound β-N-acetyl-D-glucosaminidase (Mb-NAGase). On the other hand, the quantitative value of conidia adhesion was considered as an index of its aggregation capacity. Concerning microscopic morphology, a highly negative correlation between the hyphal growth unit length (lHGU) and the specific Mb-NAGase activity was found (r = -0.915, P < 0.001). In fact, the environment was able to induce highly branched mycelia only under those culture conditions compatible with specific Mb-NAGase values equal to or higher than 190 U gdry.wt-1. Concerning macroscopic morphology, a low conidia adhesion capacity was followed by a dispersed mycelial growth. In fact, this study showed that conidia adhesion units per ml equal to or higher than 0.50 were necessary to afford pellets formation. In addition, it was also observed that once the pellet was formed the lHGU had an important influence on its final diameter. Finally, the biotechnological significance of such results was discussed as well.

Insecticidal crystal proteins from native Bacillus thuringiensis: numerical analysis and biological activity against Spodoptera frugiperda

Fourteen strains of Bacillus thuringiensis collected from both larvae showing disease symptoms and soil samples in northwest Argentina were characterized by insecticidal activity against Spodoptera frugiperda. First instar larvae and protein profile SDS-PAGE analysis of whole cell proteins not only allowed the differentiation of native Bacillus thuringiensis but also revealed the possibility of applying protein profile analysis in classification of toxicity patterns. Cluster analysis showed that there were two main groups. Interestingly, one of them only contained the most pathogenic native strains. The biomass-bound protease activity of native pathogenic isolates and the reference strain Bt 4D1 is also reported.

Towards efficient biocatalysts: photo-immobilization of a lipase on novel lysozyme amyloid-like nanofibrils

Herein, we report the preparation and characterization of a new biocatalyst based on the photo-immobilization of a lipase onto hybrid protein:sugar nanofibrils. The nanofibrils are obtained through the aggregation of hen white egg lysozyme induced by the highly sulfated glycosaminoglycan heparin. The new hybrid nanomaterial could be easily functionalized using photochemical reaction to attach lipases through dityrosine covalent bonds. Compared to the free enzyme, the photo-immobilized lipase has better thermostability and enhanced resistance to non-conventional environment. Structural and morphological characterization of the nanofibrils shows that they are compatible with amyloid-like aggregates. In addition, the supramolecular arrangement of heparin and lysozyme within the building unit of the nanofibrils is also proposed. The procedure reported herein could be useful to design a new generation of insoluble biocatalyst by a single photo-click step which is definitely cleaner and faster than conventional chemical cross-linked procedures.

Influence of Environmental Conditions on Hyphal Morphology in Pellets of Aspergillus niger: Role of β-N-Acetyl-D-Glucosaminidase

Abstract. The influence of modifications of the environmental conditions of growth on β-N-acetyl-D-glucosaminidase (EC 3.2.1.30) activity and on hyphal morphological patterns in pellets of Aspergillus niger was studied. It was found that changes in the degree of branching and, to a lesser extent, in the number of bulbous cells were directly related to the activity of the enzyme. Nevertheless, since β-N-acetyl-D-glucosaminidase is not the only enzyme involved in the lytic potential of the fungus, these findings do not exclude the possibility that other enzymes may be involved.

Chapter 10 – Biocatalysis

Biocatalysis-based technologies are becoming a burgeoning arena of research and industrial applications since the need of intensive use of natural resources with reduced pollution is now a world trend. The advance of Green Chemistry is based on the major development of many areas of the scientific knowledge which involves from the detection of enzyme molecular intermediates and products at very low concentrations, to the development of the biocatalyst ready for the challenge of industrial processes via several strategies such as enzyme immobilization, changes of protein structure, genetic databases, to tailoring the reaction media and raw material processing. In the present chapter, some fundamental topics of biocatalysis will be analyzed in terms of present and future applications at large scale.

Direct Dna Amplification from Fall Armyworm (Lepidoptera: Noctuidae) Samples

The direct amplification by PCR of the DNA in tissue samples of eggs and neonate larvae of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) was accomplished, and it is a new alternative for DNA amplification from fall armyworm samples. This method is simple, fast, economic, and accelerates studies on this polyphagous pest. Se aplico la tecnica de PCR para amplificar el DNA directamente a partir de huevos y de larvas neonatas de Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). Esta es una nueva alternativa para la amplificacion del ADN de muestras del gusano cogollero. El metodo propuesto es simple, rapido, economico y agiliza los procedimientos para diversos estudios sobre esta plaga polifaga. View this article in BioOne