Growth of Leucoagaricus gongylophorus Möller (Singer) and production of key enzymes in submerged and solid-state cultures with lignocellulosic substrates.

The aim of this study was to characterize the growth of the fungus Leucoagaricus gongylophorus LEU18496, isolated from the fungus garden of the nest of leaf cutter ants Atta mexicana. The fungus garden was cultivated in an artificial laboratory nest and the fungus further grown in submerged (SmC) and solid state (SSC) cultures with sugarcane bagasse, grass or model substrates containing CM-cellulose, xylan or lignin. The CO2 production rate with grass in SmC (Vmax 34.76 mg CO2 Lgas-1 day- 1) was almost four times than SSC (Vmax 9.49 mg CO2 Lgas-1 day- 1), while the production rate obtained in sugarcane bagasse in SmC (Vmax 16.02 mg CO2 Lgas-1 day- 1) was almost three times than that for SSC (Vmax 5.42 mg CO2 Lgas-1 day- 1). In addition, the fungus grew with defined carbon substrates mixtures in SmC, but at different rates, first xylan, followed by CM-cellulose and lignin. Endoglucanase and xylanase activities (U mgprotein-1) were detected in all cultures, the specific activity was higher in the fungus-garden, 5.2 and 1.8; followed by SSC-grass, 1.5 and 0.8, and SSC-bagasse, 0.9 and 0.8, respectively. Laccase activity in the fungus-garden was 44.8 U L- 1 and 10.9 U L- 1 in the SSC-grass. The gongylidia structures observed by environmental scanning electron microscopy were ca. 40 µm and the hyphae width ca. 5 µm. The results show that L. gongylophorus from A. mexicana have promising applications for the treatment of plant residues to release fermentable sugars and the production of high value lignocellulolytic enzymes such as endoglucanase, xylanase or laccases.

Evaluating the biological risk of functionalized multiwalled carbon nanotubes and functionalized oxygen-doped multiwalled carbon nanotubes as possible toxic, carcinogenic, and embryotoxic agents.

Carbon nanotubes (CNTs) have been a focus of attention due to their possible applications in medicine, by serving as scaffolds for cell growth and proliferation and improving mesenchymal cell transplantation and engraftment. The emphasis on the benefits of CNTs has been offset by the ample debate on the safety of nanotechnologies. In this study, we determine whether functionalized multiwalled CNTs (fMWCNTs) and functionalized oxygen-doped multiwalled CNTs (fCOxs) have toxic effects on rat mesenchymal stem cells (MSCs) in vitro by analyzing morphology and cell proliferation and, using in vivo models, whether they are able to transform MSCs in cancer cells or induce embryotoxicity. Our results demonstrate that there are statistically significant differences in cell proliferation and the cell cycle of MSCs in culture. We identified dramatic changes in cells that were treated with fMWCNTs. Our evaluation of the transformation to cancer cells and cytotoxicity process showed little effect. However, we found a severe embryotoxicity in chicken embryos that were treated with fMWCNTs, while fCOxs seem to exert cardioembryotoxicity and a discrete teratogenicity. Furthermore, it seems that the time of contact plays an important role during cell transformation and embryotoxicity. A single contact with fMWCNTs is not sufficient to transform cells in a short time; an exposure of fMWCNTs for 2 weeks led to cell transformation risk and cardioembryotoxicity effects.

Evaluation of agave fiber delignification by means of microscopy techniques and image analysis.

Recently, the use of different types of natural fibers to produce paper and textiles from agave plants has been proposed. Agave atrovirens can be a good source of cellulose and lignin; nevertheless, the microstructural changes that happen during delignification have scarcely been studied. The aim of this work was to study the microstructural changes that occur during the delignification of agave fibers by means of microscopy techniques and image analysis. The fibers of A. atrovirens were obtained from leaves using convective drying, milling, and sieving. Fibers were processed using the Acetosolv pulping method at different concentrations of acetic acid; increasing acid concentration promoted higher levels of delignification, structural damage, and the breakdown of fiber clumps. Delignification followed by spectrometric analysis and microstructural studies were carried out by light, confocal laser scanning and scanning electron microscopy and showed that the delignification process follows three stages: initial, bulk, and residual. Microscopy techniques and image analysis were efficient tools for microstructural characterization during delignification of agave fibers, allowing quantitative evaluation of the process and the development of linear prediction models. The data obtained integrated numerical and microstructural information that could be valuable for the study of pulping of lignocellulosic materials.